I have a vertical sensor like yours and the one that was recently on Ebay. However, no matter how I try I can not balance it so the pointer stays in the center of the indicator on the front of the unit. The best I have been able to manage is with the pointer near the top of the dial, but it does work there. Any ideas or suggestions would be appreciated.
Thanks
Jim Allen
Subject: Re: Sprengnether Vertical Seismo
From: meredithlamb meredithlamb@.............
Date: Fri, 15 Nov 2002 10:42:09 -0700
Hi Jim,
I had the same problem ~10 years ago with mine on ititial setup.
The most immediate problem with a "good" answer is my
shrinking memory cells (ha).
I think (without delving into the parts manuel at
this time), (us guys don't read the manuel first....ha.) is that
towards the top rear is where there is a knurled round nut that
is also a wire locking compression (screwing) clamp (I think
with a setscrew underneath); that actually connects to the
zero length spring. There was also another compression
nut further down from the top nut that needs to be loosened.
You would "overall" need to lower the wire somewhat to find
a area of the wire to clamp down on....to where.....the mass
oscillates, and can be "zeroed" the best, per the pointer from
the boom that goes over the scale on the upright
aluminum post with the boom clamp hole. The total wire
movement "might" only be ~ 1/2", but perhaps up to 1" or
more (?).
I'd level the base with the setscrews and a bubble level in both
directions first. Check and see if that does the trick with the boom
unlocked. If no success, you need to clamp the boom in place
with the locking pin in the holes provided for the front and rear
areas, so it doesn't move. The locked boom protects about
everything from damage if the spring gets loose on one end,
which it probably can/will happen potentially.
I literally marked this upper wire near a seismo part with a felt
tip pen to show where it is at the present....you know it would
need to be alittle further down than it was, once you unclamp
the wire on the top. Of course once you unclamp, the spring
contraction force will jerk it down very fast....you need to limit
this amount of movement with other outside wire holding clamps
locking vise wrench grips etc., means. Keep up marking the
wire for a past position reference. I sanded the wire to get a
clean shiny surface, to see the black marker ink.
Relock the wire, unclamp you tool clamps, unlock the boom,
and test. You may have to do this quite a number of times, to
find a nice zeroing pointer/marker place. Of course you need
to keep in mind that the setscrews and the seismo base also
play a part in this balance/zero.....and also the seismo period
length one sees, or wishes to have. If....you go down too far
then it becomes a physical effort to pull on the upper wire
(many pounds of exertion), and at the same time eyeball for the
wire mark and also be ready to use the setscrew to clamp down
on the wire. You may need a strong friend to help pull/stabilize
the wire. It can be a pain in the maximus glutomus to do this stuff,
but it did work out in the end for me. If the wire breaks, no big
deal; its common music wire. Keep your fingers away from the
spring during all of this, if it gets loose, it could break/smash
fingers
that are in the way.
Whenever you move the unit, you might expect to have to do it
again. Once its adjusted, their might be a month or two of
"settling in" waiting time, but thereafter, it usually is very
stabile...
moreso than any horizontal...but make sure it has a good
temperature stable environment if possible. If the drift is high
after acouple months; its a strong clue/suggestion that it needs
more insulation from temperature extremes. Its a very good
machine I think overall, and it offers a variety of potentials for
add-ons sensors actually.....if one is so inclined to try. Its
worth the time/effort....verticals are always the most useful,
scarce (and often difficult adjustment) machines.
If I remember correctly....the manuel doesn't cover the topic,
for the time (50+ years ago), they wanted to send out company
techs to do the setup stuff for the original buyer. All this effort
will acquaint you well with the machine. I think it took me
several (grumbling, fumbling, learning) days to get it adjusted....ha.
Take care, Meredith Lamb
RADIOTEL@....... wrote:
> I have a vertical sensor like yours and the one that was recently on
> Ebay. However, no matter how I try I can not balance it so the
> pointer stays in the center of the indicator on the front of the
> unit. The best I have been able to manage is with the pointer near
> the top of the dial, but it does work there. Any ideas or suggestions
> would be appreciated.
> Thanks
> Jim Allen
Hi Jim,
I had the same problem ~10 years ago with mine on ititial setup.
The most immediate problem with a "good" answer is my
shrinking memory cells (ha).
I think (without delving into the parts manuel at
this time), (us guys don't read the manuel first....ha.) is that
towards the top rear is where there is a knurled round nut that
is also a wire locking compression (screwing) clamp (I think
with a setscrew underneath); that actually connects to the
zero length spring. There was also another compression
nut further down from the top nut that needs to be loosened.
You would "overall" need to lower the wire somewhat to find
a area of the wire to clamp down on....to where.....the mass
oscillates, and can be "zeroed" the best, per the pointer from
the boom that goes over the scale on the upright
aluminum post with the boom clamp hole. The total wire
movement "might" only be ~ 1/2", but perhaps up to 1" or
more (?).
I'd level the base with the setscrews and a bubble level in both
directions first. Check and see if that does the trick with the
boom
unlocked. If no success, you need to clamp the boom in place
with the locking pin in the holes provided for the front and rear
areas, so it doesn't move. The locked boom protects about
everything from damage if the spring gets loose on one end,
which it probably can/will happen potentially.
I literally marked this upper wire near a seismo part with a felt
tip pen to show where it is at the present....you know it would
need to be alittle further down than it was, once you unclamp
the wire on the top. Of course once you unclamp, the spring
contraction force will jerk it down very fast....you need to limit
this amount of movement with other outside wire holding clamps
locking vise wrench grips etc., means. Keep up marking the
wire for a past position reference. I sanded the wire to get
a
clean shiny surface, to see the black marker ink.
Relock the wire, unclamp you tool clamps, unlock the boom,
and test. You may have to do this quite a number of times, to
find a nice zeroing pointer/marker place. Of course you need
to keep in mind that the setscrews and the seismo base also
play a part in this balance/zero.....and also the seismo period
length one sees, or wishes to have. If....you go down too far
then it becomes a physical effort to pull on the upper wire
(many pounds of exertion), and at the same time eyeball for the
wire mark and also be ready to use the setscrew to clamp down
on the wire. You may need a strong friend to help pull/stabilize
the wire. It can be a pain in the maximus glutomus to do this
stuff,
but it did work out in the end for me. If the wire breaks, no
big
deal; its common music wire. Keep your fingers away from the
spring during all of this, if it gets loose, it could break/smash fingers
that are in the way.
Whenever you move the unit, you might expect to have to do it
again. Once its adjusted, their might be a month or two of
"settling in" waiting time, but thereafter, it usually is very stabile...
moreso than any horizontal...but make sure it has a good
temperature stable environment if possible. If the drift is high
after acouple months; its a strong clue/suggestion that it needs
more insulation from temperature extremes. Its a very good
machine I think overall, and it offers a variety of potentials for
add-ons sensors actually.....if one is so inclined to try. Its
worth the time/effort....verticals are always the most useful,
scarce (and often difficult adjustment) machines.
If I remember correctly....the manuel doesn't cover the topic,
for the time (50+ years ago), they wanted to send out company
techs to do the setup stuff for the original buyer. All this
effort
will acquaint you well with the machine. I think it took me
several (grumbling, fumbling, learning) days to get it adjusted....ha.
Take care, Meredith Lamb
RADIOTEL@....... wrote:
I have a vertical
sensor like yours and the one that was recently on Ebay. However,
no matter how I try I can not balance it so the pointer stays in the center
of the indicator on the front of the unit. The best I have been able
to manage is with the pointer near the top of the dial, but it does work
there. Any ideas or suggestions would be appreciated.
Thanks
Jim Allen
Subject: Re: STM 8 (previous Sprengnether subject email)
From: meredithlamb meredithlamb@.............
Date: Fri, 15 Nov 2002 11:56:54 -0700
Hi Karl and all,
Barry wrote:
> Hi Meredith I have wanted to put a web site together like several
> of you folks have so nicely done but I seem to have a problem with
> documentation. I have made some photos but not to many yet. Written
> descriptions----well not yet. I can briefly describe what I have done
> wrt the SMT8 style verticals. I think of the SMT8 in four
> parts. 1. the mechanical - boom, leaf spring, hinges.On
> my first sensor I tried as closely as possible to duplicate the the
> SMT8 geometry. The only change I made was to remove part of the leaf
> spring support where it attaches to the end pins so I could slightly
> squeeze the ends of the bent leaf spring together and quickly remove
> it from the assembly w/o tools.
>
> Sounds interesting on the mechanical change, although I don't
> totally understand it.
>
>
> On the second SMT8 I reproduced the first sensor but made the boom
> about 10 " long to try to make it more portable (for possible field
> use in an ammo box). 2. the displacement sensorIn the
> first sensor, I installed a homemade LVDT with phase shift oscillator
> and the demodulator that Karl Cunningham has described. In the second
> sensor I installed the VRDT hardware as STM described but with phase
> shift oscillator, instrumentation amp to sum and Karl's demodulator.
> Both work well and are quite linear. Side note: I calibrate the
> displacement sensors with a "diving board" type device that I
> calibrated with precision weights. I found it was easier to apply a
> precise weight than a small deflection directly. All the circuitry for
> either can be crammed on a 2X6.5 size breadboard. Not too complicated
> of circuitry, mostly just dual opamps.
>
> Most interesting on the LVDT switch from the LRDT original design
> on one of your instruments! Am not really "up" to either; but its
> interesting on the switching sensor capability you've already done
> and the success.
>
> Perhaps the biggest thing I "seem" to see, is that Seans
> original LRDT transformers are in likelyhood kind of a crude
> nonlinear wire wrapping; whereas, your LVDT, is a painstaking
> relatively
> precision wire layed device. Yet.....according to Seans website, his
> LRDT is sensitive to a incredible .1nm. I've zero experience
> but it makes me wonder further about coils themselves between
> the two. It would seem the LRDT is much simpler to make and
> more sensitive overall. Interesting.
>
> 3. the feedback circuitryI used the Mathcad equations
> STM suggested. 4. mechanical adjustment control.There are
> some adjustments I found necessary as STM had described in depth. The
> vertical is not as sensitive to tilting but is sensitive to
> temperature and the initial relaxation of the leaf spring. For
> temperature correction I installed a bimetal thermometer coil near the
> boom. With some trial and error positioning and thermal insulation I
> was able to remove a substantial amount of this temperature variation.
> For zero adjustment I used the Edmond Scientific low rpm motor and
> threaded rod and sliding weight. Works well.
>
> Quite a nice additon on the bi-metal thermometer coil!
>
> Take care, Meredith Lamb
Hi Karl and all,
Barry wrote:
Hi
Meredith I have wanted to put a web site together
like several of you folks have so nicely done but I seem to have a problem
with documentation. I have made some photos but not to many yet.
Written descriptions----well not yet. I can briefly describe what
I have done wrt the SMT8 style verticals. I think
of the SMT8 in four parts.
1. the mechanical - boom, leaf spring, hinges.On my first sensor I tried
as closely as possible to duplicate the the SMT8 geometry. The only change
I made was to remove part of the leaf spring support where it attaches
to the end pins so I could slightly squeeze the ends of the bent leaf spring
together and quickly remove it from the assembly w/o tools.
Sounds interesting on the mechanical
change, although I don't
totally understand it.
On the second SMT8 I reproduced the
first sensor but made the boom about 10 " long to try to make it more portable
(for possible field use in an ammo box).
2. the displacement sensorIn the first sensor, I installed a homemade
LVDT with phase shift oscillator and the demodulator that Karl Cunningham
has described. In the second sensor I installed the VRDT hardware
as STM described but with phase shift oscillator, instrumentation amp to
sum and Karl's demodulator. Both work well and are quite linear. Side note:
I calibrate the displacement sensors with a "diving board" type device
that I calibrated with precision weights. I found it was easier to apply
a precise weight than a small deflection directly. All the circuitry for
either can be crammed on a 2X6.5 size breadboard. Not too complicated of
circuitry, mostly just dual opamps.
Most interesting on the LVDT switch
from the LRDT original design
on one of your instruments!
Am not really "up" to either; but its
interesting on the switching sensor
capability you've already done
and the success.
Perhaps the biggest thing I "seem"
to see, is that Seans
original LRDT transformers are in
likelyhood kind of a crude
nonlinear wire wrapping; whereas,
your LVDT, is a painstaking relatively
precision wire layed device.
Yet.....according to Seans website, his
LRDT is sensitive to a incredible
..1nm. I've zero experience
but it makes me wonder further about
coils themselves between
the two. It would seem the LRDT
is much simpler to make and
more sensitive overall. Interesting.
3. the feedback circuitryI used the Mathcad equations STM suggested.
4. mechanical adjustment control.There are some adjustments I found necessary
as STM had described in depth. The vertical is not as sensitive to
tilting but is sensitive to temperature and the initial relaxation of the
leaf spring. For temperature correction I installed a bimetal thermometer
coil near the boom. With some trial and error positioning and thermal insulation
I was able to remove a substantial amount of this temperature variation.
For zero adjustment I used the Edmond Scientific low rpm motor and threaded
rod and sliding weight. Works well.
Quite a nice additon on the bi-metal
thermometer coil!
Take care, Meredith Lamb
Subject: Re: STM 8 (LVDT subject)
From: meredithlamb meredithlamb@.............
Date: Fri, 15 Nov 2002 13:08:27 -0700
Hi Chris and all,
This message is more with the LVDT aspect than with the
original LRDT sensor with Sean Morrisseys STM-8 design.
ChrisAtUpw@....... wrote:
> In a message dated 13/11/02, meredithlamb@............. writes:
>
> Regardless, its "still"
>
>> likely the best broadband vertical design around for its
>> cheapest home building approach..... As I recall, one or two people
>> were considering other sensor / amplifier methods outside of the
>> original design, but I've no idea of how that went.
>
> Agreed, but there are several sensor approaches which can be
> successful. To my mind, there is a distinct shortage of amateur 'off
> the shelf' sensor designs capable of giving near professional
> resolution and stability. There is only one LVDT kit sensor available
> with a PCB, to my knowledge, which can give about 7 nano metres
> resolution at 10 Hz over +/-6 mm, with a max range of +/-12 mm.
Presume its the Italian, Nuova Electronica unit (?), you've been
working with/on over time?
Perhaps the greatest curiosity item I wonder about their
transformer part, is whether its really a precision wound
unit like mentioned as a (professional) necessity as on other web
sites? It appears to be much like other general looking transformer/s.
Without any access I'd guess its somewhat linearly wound
but no where near precision.
All this is leading up to the question of whether a fairly
linear wound (but not exactly precisely layered) coil "could"
somewhat work simarily (with less sensitivity) with the same
general ferrite core type setup. Such coils are rather scarce
I'am sure. It would probably leave out any and all relay coils
on the general "market". It "might" be more prevalent to
some salvagable coil transformers though.
Just some (unexperienced) thoughts. I think the Nuova item
costs around $103 US dollars (PCB and LVDT) plus
whatever shipping/handling. Sometimes I think that a
homebrew LVDT with perhaps a Phillips or Analog IC
(and other parts) might be a cheaper alternative......but
probably more costly for any R&D overall.
Take care, Meredith Lamb
Hi Chris and all,
This message is more with the LVDT aspect than with the
original LRDT sensor with Sean Morrisseys STM-8 design.
ChrisAtUpw@....... wrote:
In a message
dated 13/11/02, meredithlamb@............. writes:
Regardless, its "still"
likely
the best broadband vertical design around for its
cheapest home building approach.....
As I recall, one or two people were considering other sensor / amplifier
methods outside of the original design, but I've no idea of how that went.
Agreed, but there are several sensor approaches which can be successful.
To my mind, there is a distinct shortage of amateur 'off the shelf' sensor
designs capable of giving near professional resolution and stability. There
is only one LVDT kit sensor available with a PCB, to my knowledge, which
can give about 7 nano metres resolution at 10 Hz over +/-6 mm, with a max
range of +/-12 mm.
Presume its the Italian, Nuova Electronica unit (?), you've been
working with/on over time?
Perhaps the greatest curiosity item I wonder about their
transformer part, is whether its really a precision wound
unit like mentioned as a (professional) necessity as on other web
sites? It appears to be much like other general looking transformer/s.
Without any access I'd guess its somewhat linearly wound
but no where near precision.
All this is leading up to the question of whether a fairly
linear wound (but not exactly precisely layered) coil "could"
somewhat work simarily (with less sensitivity) with the same
general ferrite core type setup. Such coils are rather scarce
I'am sure. It would probably leave out any and all relay coils
on the general "market". It "might" be more prevalent to
some salvagable coil transformers though.
Just some (unexperienced) thoughts. I think the Nuova item
costs around $103 US dollars (PCB and LVDT) plus
whatever shipping/handling. Sometimes I think that a
homebrew LVDT with perhaps a Phillips or Analog IC
(and other parts) might be a cheaper alternative......but
probably more costly for any R&D overall.
Take care, Meredith Lamb
Subject: Re: STM 8 (LVDT subject)
From: "Mauro Mariotti" mariotti@.........
Date: Fri, 15 Nov 2002 22:59:20 +0100
Hi All,
I worked very much with this LVDT.
It is based on the Phllips NE5521N phase comparator.
I can supply you the schematic if needed.
The cost of the unit is 50$ for the circuit and 50$ for the mechanic to=20
build up a complete horizontal sensor like to S-G type.
I never disassembled the LVDT coils to but I can do it I have some spare
part in my lab.
The LX922 kit is no longer producted, only some spare parts are =
available.
The actual Nuova Elettronica production is on LX1358.
All the system was conceived to use a high-speed thermal printer
for producing seismograms.
Actually N.E. producing a A/D interface the LX1500 that is a single
channel fixed 50 SPS at 16 bit with the AD7715 converter.
It have no syncronization clock.
It can be used also with SEISMOWIN.
Anwyay that LVDT can be used with any kind of a/d if the DC
component is removed (the output is 0-12V at 6V zero offset).
If needed I can provide more info about.
The results of that LVDT are very good but accurate shielding of
the coils and the circuit is needed to avoid interference and keep
low the noise.
Regards
Mauro
Just some (unexperienced) thoughts. I think the Nuova item=20
costs around $103 US dollars (PCB and LVDT) plus=20
whatever shipping/handling. Sometimes I think that a=20
homebrew LVDT with perhaps a Phillips or Analog IC=20
(and other parts) might be a cheaper alternative......but=20
probably more costly for any R&D overall.=20
Hi All,
I worked very much with this =
LVDT.
It is based on the Phllips NE5521N =
phase=20
comparator.
I can supply you the schematic if=20
needed.
The cost of the unit is 50$ for the =
circuit and 50$=20
for the mechanic to
build up a complete horizontal sensor =
like to S-G=20
type.
I never disassembled the LVDT coils to =
but I can do=20
it I have some spare
part in my lab.
The LX922 kit is no longer producted, =
only some=20
spare parts are available.
The actual Nuova Elettronica production =
is on=20
LX1358.
All the system was conceived to use a =
high-speed=20
thermal printer
for producing seismograms.
Actually N.E. producing a A/D interface =
the LX1500=20
that is a single
channel fixed 50 SPS at 16 bit with the =
AD7715=20
converter.
It have no syncronization =
clock.
It can be used also with =
SEISMOWIN.
Anwyay that LVDT can be used with any =
kind of a/d=20
if the DC
component is removed (the output is =
0-12V at 6V=20
zero offset).
If needed I can provide more info=20
about.
The results of that LVDT are very good =
but accurate=20
shielding of
the coils and the circuit is needed to =
avoid=20
interference and keep
low the noise.
Regards
Mauro
Just some (unexperienced) thoughts. I think the Nuova item =
costs=20
around $103 US dollars (PCB and LVDT) plus
whatever=20
shipping/handling. Sometimes I think that a
homebrew LVDT =
with=20
perhaps a Phillips or Analog IC
(and other parts) might be a =
cheaper=20
alternative......but
probably more costly for any R&D overall. =
Subject: Re: STM 8 (LVDT subject)
From: ChrisAtUpw@.......
Date: Sat, 16 Nov 2002 14:29:47 EST
In a message dated 15/11/02, meredithlamb@............. writes:
> >> Agreed, but there are several distance transducer approaches whic=
h=20
>> can be successful. To my mind, there is a distinct shortage of amateur=20
>> 'off the shelf' sensor designs capable of giving near professional=20
>> resolution and stability. There is only one LVDT Kit sensor available wit=
h=20
>> a PCB, to my knowledge, which can give about 7 nano metres resolution at=20
>>=20
> Presume its the Italian, Nuova Elettronica unit (?), you've been working=20
>=20
Hi Meredith,
I have done some experiments modifying / improving my Nuova=20
Elettronica LVDT board, reducing the two pole detector filter to 10 Hz, whic=
h=20
is more suitable for seismic use, changing the output opamp to a low noise=20
type and increasing the time constant of the high pass filter, along with=20
several other small changes. NE seemed to have used a circuit designed by=20
Philips for wider bandwidth commercial LVDT applications. I have also been=20
working on other magnetic sensor systems using the Philips NE5521 LVDT chip,=
=20
including modified transformers, somewhat like Sean's, some using ferrite=20
components and lately, a capacitative system. I have a full write up nearly=20
finished.=20
> Perhaps the greatest curiosity item I wonder about their transformer part,=
=20
> is whether its really a precision wound unit like mentioned as a=20
> (professional) necessity as on other web sites? It appears to be much lik=
e=20
> other general looking transformers. Without any access I'd guess its=20
>=20
If you want to measure several inches of movement and require a linea=
r=20
response, you may need a precision linear winding. If you only want a few mm=
=20
and the field of the sensor rod can be sensed over a physically much larger=20
sensor winding, you just need the windings to stay in a fixed position. Ther=
e=20
will of course be thermal expansion and changes of resistance with=20
temperature, but these effects are very small over the 10 Hz bandwidth and=20
the 5 to 30 sec of the high pass filter time constant. =20
> Perhaps the biggest thing I "seem" to see, is that Seans original LRDT=20
> transformers are in likelyhood kind of a crude nonlinear wire wrapping;=20
> whereas, your LVDT, is a painstaking relatively precision wire layered=20
>=20
With Sean's variable reluctance transformer sensor, the magnetic=20
circuit is defined by the position of the flat iron armature plate and the=20
iron polepieces. In a LVDT, the interaction is between the position of a=20
magnetised armature and the varying distance it moves inside the sensor coil=
,=20
so the coil needs to be quite uniformly wound. For a description of an LVDT,=
=20
see http=
://www.msiusa.com/schaevitz/pdf/lvdt/LVDT_Intro.pdf It is not too=20
difficult to make even windings, so long as you do not use extremely fine=20
wire, do not try to wind too fast, slow up right at the end of each layer=20
and, most importantly, use very thin paper, like cigarette or tissue paper,=20
for interleaving each layer. This makes it easy to spot and correct any=20
overwinding or incorrectly spaced turns. It also makes winding easier and=20
helps to prevent shorted turns in between layers. I made two matched 40,000=20
turn precision differential transformer coils this way, for measuring=20
paramagnetic susceptibility. A very small plastic tube makes a good wire=20
guide. It is also possible to just layer wind two LVDT secondaries end to en=
d=20
on a sensor tube and use a ferrite or powder iron cored choke to provide the=
=20
magnetic excitation. This avoids having to wind a central primary magnetisin=
g=20
section in between, or over the top of the secondaries.
=20
Yet.....according to Seans website, his LRDT is sensitive to a incredible=20
0.1nm. I've=20
> zero experience but it makes me wonder further about coils themselves=20
> between=20
> the two. It would seem the LRDT is much simpler to make and more sensitiv=
e=20
>=20
Coupled with the very high sensitivity of Sean's transducer, the=20
movement range is small, perhaps +/-0.5 mm in a 2 mm total gap, and the=20
output is only linear for a limited range around the zero position. This is=20
just fine for a feedback seismometer, where you try to hold the armature=20
position constant. The out of range signal increases dramatically before=20
saturating, which can be bad news if the seismometer feedback system gets ou=
t=20
of lock.=20
> All this is leading up to the question of whether a fairly linear wound (b=
ut=20
> not exactly precisely layered) coil "could" somewhat work simarily (with=20
> less sensitivity) with the same general ferrite core type setup. Such=20
>=20
If you have an E core transformer type winding, the magnetic flux is=20
linked strongly to the winding, so great winding precision is not required,=20
only a good physical stability. The magnetic field interactions are=20
controlled by the positions and separations of the iron laminations, so thes=
e=20
need to be firmly fixed. These E core types can be either modified audio=20
transformers similar to Sean's, ferrite cup transformers with DIY windings,=20=
a=20
linear differential reluctance system of the magslip type, or two physically=
=20
large coils pairs bridged by a ferrite rod, like the NE type.
J
> ust some (unexperienced) thoughts. I think the Nuova item costs around $1=
03=20
> US dollars (PCB and LVDT) plus whatever shipping/handling. Sometimes I=20
> think that a homebrew LVDT with perhaps a Phillips or Analog IC (and other=
=20
> parts) might be a cheaper alternative......but probably more costly for an=
y=20
> R&
The two Analogue Devices LVDT chips have a relatively high noise floo=
r=20
and are not suitable for our use. The Philips NE5521 device is about 1/3 the=
=20
price and you can get right down to the intrinsic opamp noise level. =20
The LX1358 Kit price is =E2=82=AC 51.65 + Carriage. Looking up today'=
s=20
exchange rate, this is just US $51.23 !! There will be a charge on your=20
Credit Card for the currency conversion and the exchange rate will be lower=20
than the International Banking Rate quoted. Air Mail packets are reasonably=20
priced and may take 10 days to arrive. Be warned that International Carriers=
=20
may have a minimum charge of near $50 for any packet! They seem to be only=20
relatively reasonably priced within the USA.=20
=20
With a LX1358, I get ~7 nano metre resolution over a +/-6 mm=20
accurately linear range, with 65 mV / micron output. The output is 10% down=20
at +/-12 mm and 20% down at +/-15 mm, since the ''out of range'' response is=
=20
of the usual S shape. This wide range was designed for Lehman type systems,=20
but the sensor will work equally well on simple pendulums.
Regards,
Chris Chapman
In a message dated 15/11/=
02, meredithlamb@............. writes:
Agreed, but there are sever=
al distance transducer approaches which can be successful. To my mind, there=
is a distinct shortage of amateur 'off the shelf' sensor designs capable of=
giving near professional resolution and stability. There is only one LVDT K=
it sensor available with a PCB, to my knowledge, which can give about 7 nano=
metres resolution at 10 Hz over +/-6 mm, with a max range of +/-12 mm.
Presume its the Italian, Nuova Elettronica unit (?), you've been working=
with / on over time?
Hi Meredith,
I have done some experiments modify=
ing / improving my Nuova Elettronica LVDT board, reducing the two pole detec=
tor filter to 10 Hz, which is more suitable for seismic use, changing=20=
the output opamp to a low noise type and increasing the time constant of the=
high pass filter, along with several other small changes. NE seemed to have=
used a circuit designed by Philips for wider bandwidth commercial LVDT appl=
ications. I have also been working on other magnetic sensor systems using th=
e Philips NE5521 LVDT chip, including modified transformers, somewhat like S=
ean's, some using ferrite components and lately, a capacitative system. I ha=
ve a full write up nearly finished.=20
Perhaps the greatest curios=
ity item I wonder about their transformer part, is whether its really a prec=
ision wound unit like mentioned as a (professional) necessity as on other we=
b sites? It appears to be much like other general looking transformers=
.. Without any access I'd guess its somewhat linearly wound but no where near=
precision.
If you want to measure several inch=
es of movement and require a linear response, you may need a precision linea=
r winding. If you only want a few mm and the field of the sensor rod can be=20=
sensed over a physically much larger sensor winding, you just need the windi=
ngs to stay in a fixed position. There will of course be thermal expansion a=
nd changes of resistance with temperature, but these effects are very small=20=
over the 10 Hz bandwidth and the 5 to 30 sec of the high pass filter time co=
nstant.
Perhaps the biggest thing I=
"seem" to see, is that Seans original LRDT transformers are in likelyhood k=
ind of a crude nonlinear wire wrapping; whereas, your LVDT, is a painstaking=
relatively precision wire layered device.
With Sean's variable reluctance tra=
nsformer sensor, the magnetic circuit is defined by the position of the flat=
iron armature plate and the iron polepieces. In a LVDT, the interaction is=20=
between the position of a magnetised armature and the varying distance it mo=
ves inside the sensor coil, so the coil needs to be quite uniformly wound. F=
or a description of an LVDT, see http://www.msiusa.com/schaevitz/pdf/lvdt/LVDT_Intro=
..pdf It is not too difficult to make even windings, so long as you=
do not use extremely fine wire, do not try to wind too fast, slow up right=20=
at the end of each layer and, most importantly, use very thin paper, like ci=
garette or tissue paper, for interleaving each layer. This makes it easy to=20=
spot and correct any overwinding or incorrectly spaced turns. It also makes=20=
winding easier and helps to prevent shorted turns in between layers. I made=20=
two matched 40,000 turn precision differential transformer coils this way, f=
or measuring paramagnetic susceptibility. A very small plastic tube makes a=20=
good wire guide. It is also possible to just layer wind two LVDT secondaries=
end to end on a sensor tube and use a ferrite or powder iron cored choke to=
provide the magnetic excitation. This avoids having to wind a central prima=
ry magnetising section in between, or over the top of the secondaries.
=20
Yet.....according to Seans website, his LRDT is sensitive to a incredib=
le 0.1nm. I've=20
zero experience but it make=
s me wonder further about coils themselves between=20
the two. It would seem the LRDT is much simpler to make and more s=
ensitive overall.
Coupled with the very high sensitiv=
ity of Sean's transducer, the movement range is small, perhaps +/-0.5 mm in=20=
a 2 mm total gap, and the output is only linear for a limited range around t=
he zero position. This is just fine for a feedback seismometer, where you tr=
y to hold the armature position constant. The out of range signal increases=20=
dramatically before saturating, which can be bad news if the seismometer fee=
dback system gets out of lock.=20
All this is leading up to t=
he question of whether a fairly linear wound (but not exactly precisely laye=
red) coil "could" somewhat work simarily (with less sensitivity) with the sa=
me general ferrite core type setup. Such coils are rather scarce I'am=20=
sure.
If you have an E core transformer t=
ype winding, the magnetic flux is linked strongly to the winding, so great w=
inding precision is not required, only a good physical stability. The magnet=
ic field interactions are controlled by the positions and separations of the=
iron laminations, so these need to be firmly fixed. These E core types can=20=
be either modified audio transformers similar to Sean's, ferrite cup transfo=
rmers with DIY windings, a linear differential reluctance system of the mags=
lip type, or two physically large coils pairs bridged by a ferrite rod, like=
the NE type.
J
ust some (unexperienced) th=
oughts. I think the Nuova item costs around $103 US dollars (PCB and L=
VDT) plus whatever shipping/handling. Sometimes I think that a homebre=
w LVDT with perhaps a Phillips or Analog IC (and other parts) might be a che=
aper alternative......but probably more costly for any R&D overall.
The two Analogue Devices LVDT chips=
have a relatively high noise floor and are not suitable for our use. The Ph=
ilips NE5521 device is about 1/3 the price and you can get right down to the=
intrinsic opamp noise level.
The LX1358 Kit price is =E2=82=AC 5=
1.65 + Carriage. Looking up today's exchange rate, this is just US $51.23=
!! There will be a charge on your Credit Card for the currency conversi=
on and the exchange rate will be lower than the International Banking Rate q=
uoted. Air Mail packets are reasonably priced and may take 10 days to arrive=
.. Be warned that International Carriers may have a minimum charge of near $5=
0 for any packet! They seem to be only relatively reasonably priced within t=
he USA.=20
=20
With a LX1358, I get ~7 nano metre=20=
resolution over a +/-6 mm accurately linear range, with 65 mV / micron outpu=
t. The output is 10% down at +/-12 mm and 20% down at +/-15 mm, since the ''=
out of range'' response is of the usual S shape. This wide range was designe=
d for Lehman type systems, but the sensor will work equally well on simple p=
endulums.
Regards,
Chris Chapman
Subject: Re: STM 8 (LVDT subject)
From: meredithlamb meredithlamb@.............
Date: Sat, 16 Nov 2002 15:32:10 -0700
Hi Mauro and all,
Thanks for the notes. I see your reference to the LX922 &
LX1358 on the web: The obsolete LX922 seismometer in its
entirety, certainly was a large unit. Is the same LVDT coil and circuit
board used on such, the same as on the small pendulum LX1358
that you know of?
http://mariottim.interfree.it/doc13_e.htm
Yes, if you can, and want to, it would be interesting to see
just what they used in the LVDT squarish transformer/s inasfar
as whether its precision laid out, or more ~jumbo wound.
They are somewhat large, and I suspect they are salvaged
coils meant originally for another use....but I could always be
wrong. In a sense, even if they are not precision, it kind of
suggests that other transformers could work also.....but with
a reduced sensitivity compared to precision wound LVDT's
(but still very good overall).
Mauro Mariotti wrote:
> Hi All, I worked very much with this LVDT.It is based on the Phllips
> NE5521N phase comparator.I can supply you the schematic if needed.The
> cost of the unit is 50$ for the circuit and 50$ for the mechanic
> tobuild up a complete horizontal sensor like to S-G type.I never
> disassembled the LVDT coils to but I can do it I have some sparepart
> in my lab.
Hi Mauro and all,
Thanks for the notes. I see your reference to the LX922 &
LX1358 on the web: The obsolete LX922 seismometer in its
entirety, certainly was a large unit. Is the same LVDT coil and
circuit
board used on such, the same as on the small pendulum LX1358
that you know of?
http://mariottim.interfree.it/doc13_e.htm
Yes, if you can, and want to, it would be interesting to see
just what they used in the LVDT squarish transformer/s inasfar
as whether its precision laid out, or more ~jumbo wound.
They are somewhat large, and I suspect they are salvaged
coils meant originally for another use....but I could always be
wrong. In a sense, even if they are not precision, it kind of
suggests that other transformers could work also.....but with
a reduced sensitivity compared to precision wound LVDT's
(but still very good overall).
Mauro Mariotti wrote:
Hi
All, I worked very much
with this LVDT.It is based on the Phllips NE5521N phase comparator.I can
supply you the schematic if needed.The cost of the unit is 50$ for the
circuit and 50$ for the mechanic tobuild up a complete horizontal sensor
like to S-G type.I never disassembled the LVDT coils to but I can do it
I have some sparepart in my lab.
Subject: Re: STM 8 (LVDT subject)
From: meredithlamb meredithlamb@.............
Date: Sat, 16 Nov 2002 16:53:12 -0700
Hi Chris and all,
ChrisAtUpw@....... wrote:
>> > Agreed, but there are several distance transducer approaches which
>> > can be successful. To my mind, there is a distinct shortage of
>> > amateur 'off the shelf' sensor designs capable of giving near
>> > professional resolution and stability. There is only one LVDT Kit
>> > sensor available with a PCB, to my knowledge, which can give about
>> > 7 nano metres resolution at 10 Hz over +/-6 mm, with a max range of
>> > +/-12 mm.
>>
>>
>> Presume its the Italian, Nuova Elettronica unit (?), you've been
>> working with / on over time?
>
> Hi Meredith,
>
> I have done some experiments modifying / improving my Nuova
> Elettronica LVDT board, reducing the two pole detector filter to 10
> Hz, which is more suitable for seismic use, changing the output opamp
> to a low noise type and increasing the time constant of the high pass
> filter, along with several other small changes. NE seemed to have used
> a circuit designed by Philips for wider bandwidth commercial LVDT
> applications. I have also been working on other magnetic sensor
> systems using the Philips NE5521 LVDT chip, including modified
> transformers, somewhat like Sean's, some using ferrite components and
> lately, a capacitative system. I have a full write up nearly finished.
Your full write up should be VERY interesting!!
>> Perhaps the greatest curiosity item I wonder about their transformer
>> part, is whether its really a precision wound unit like mentioned as
>> a (professional) necessity as on other web sites? It appears to be
>> much like other general looking transformers. Without any access I'd
>> guess its somewhat linearly wound but no where near precision.
>
> If you want to measure several inches of movement and require a linear
> response, you may need a precision linear winding. If you only want a
> few mm and the field of the sensor rod can be sensed over a physically
> much larger sensor winding, you just need the windings to stay in a
> fixed position. There will of course be thermal expansion and changes
> of resistance with temperature, but these effects are very small over
> the 10 Hz bandwidth and the 5 to 30 sec of the high pass filter time
> constant.
>
>
>> Perhaps the biggest thing I "seem" to see, is that Seans original
>> LRDT transformers are in likelyhood kind of a crude nonlinear wire
>> wrapping; whereas, your LVDT, is a painstaking relatively precision
>> wire layered device.
>
> With Sean's variable reluctance transformer sensor, the magnetic
> circuit is defined by the position of the flat iron armature plate and
> the iron polepieces. In a LVDT, the interaction is between the
> position of a magnetised armature and the varying distance it moves
> inside the sensor coil, so the coil needs to be quite uniformly wound.
> For a description of an LVDT, see
> http://www.msiusa.com/schaevitz/pdf/lvdt/LVDT_Intro.pdf It is not too
> difficult to make even windings, so long as you do not use extremely
> fine wire, do not try to wind too fast, slow up right at the end of
> each layer and, most importantly, use very thin paper, like cigarette
> or tissue paper, for interleaving each layer. This makes it easy to
> spot and correct any overwinding or incorrectly spaced turns. It also
> makes winding easier and helps to prevent shorted turns in between
> layers. I made two matched 40,000 turn precision differential
> transformer coils this way, for measuring paramagnetic susceptibility.
> A very small plastic tube makes a good wire guide. It is also possible
> to just layer wind two LVDT secondaries end to end on a sensor tube
> and use a ferrite or powder iron cored choke to provide the magnetic
> excitation. This avoids having to wind a central primary magnetising
> section in between, or over the top of the secondaries.
>
> Yet.....according to Seans website, his LRDT is sensitive to a
> incredible 0.1nm. I've
>
>> zero experience but it makes me wonder further about coils
>> themselves between
>> the two. It would seem the LRDT is much simpler to make and more
>> sensitive overall.
>
> Coupled with the very high sensitivity of Sean's transducer, the
> movement range is small, perhaps +/-0.5 mm in a 2 mm total gap, and
> the output is only linear for a limited range around the zero
> position. This is just fine for a feedback seismometer, where you try
> to hold the armature position constant. The out of range signal
> increases dramatically before saturating, which can be bad news if the
> seismometer feedback system gets out of lock.
Seans reluctance sensor sounds like it could be used in a "S-G" also,
although one might have a devil of a time especially when any
kind of small height S-G feedback system, might influence the sensor.
Perhaps a fixed eddy current damping system might be workable,
if far enough away from the sensor itself.
>> All this is leading up to the question of whether a fairly linear
>> wound (but not exactly precisely layered) coil "could" somewhat work
>> simarily (with less sensitivity) with the same general ferrite core
>> type setup. Such coils are rather scarce I'am sure.
>
> If you have an E core transformer type winding, the magnetic flux is
> linked strongly to the winding, so great winding precision is not
> required, only a good physical stability. The magnetic field
> interactions are controlled by the positions and separations of the
> iron laminations, so these need to be firmly fixed. These E core types
> can be either modified audio transformers similar to Sean's, ferrite
> cup transformers with DIY windings, a linear differential reluctance
> system of the magslip type, or two physically large coils pairs
> bridged by a ferrite rod, like the NE type.
>
>> Just some (unexperienced) thoughts. I think the Nuova item costs
>> around $103 US dollars (PCB and LVDT) plus whatever
>> shipping/handling. Sometimes I think that a homebrew LVDT with
>> perhaps a Phillips or Analog IC (and other parts) might be a cheaper
>> alternative......but probably more costly for any R&D overall.
>
> The two Analogue Devices LVDT chips have a relatively high noise floor
> and are not suitable for our use. The Philips NE5521 device is about
> 1/3 the price and you can get right down to the intrinsic opamp noise
> level.
>
> The LX1358 Kit price is € 51.65 + Carriage. Looking up today's
> exchange rate, this is just US $51.23 !! There will be a charge on
> your Credit Card for the currency conversion and the exchange rate
> will be lower than the International Banking Rate quoted. Air Mail
> packets are reasonably priced and may take 10 days to arrive. Be
> warned that International Carriers may have a minimum charge of near
> $50 for any packet! They seem to be only relatively reasonably priced
> within the USA.
Am missing something here....whats the difference between a "air mail
packet", and a, "International Carriers"? Did Nuova offer the
distinction
when you got your LVDT? Airmail v/s "ground" (ship)?
> With a LX1358, I get ~7 nano metre resolution over a +/-6 mm
> accurately linear range, with 65 mV / micron output. The output is 10%
> down at +/-12 mm and 20% down at +/-15 mm, since the ''out of range''
> response is of the usual S shape. This wide range was designed for
> Lehman type systems, but the sensor will work equally well on simple
> pendulums.
Thats quite a large sensor mm/mv output! Thanks for all the "feedback"
info!
Take care, Meredith
Hi Chris and all,
ChrisAtUpw@....... wrote:
Agreed,
but there are several distance transducer approaches which can be successful.
To my mind, there is a distinct shortage of amateur 'off the shelf' sensor
designs capable of giving near professional resolution and stability. There
is only one LVDT Kit sensor available with a PCB, to my knowledge, which
can give about 7 nano metres resolution at 10 Hz over +/-6 mm, with a max
range of +/-12 mm.
Presume its the Italian,
Nuova Elettronica unit (?), you've been working with / on over time?
Hi Meredith,
I have done some experiments
modifying / improving my Nuova Elettronica LVDT board, reducing the two
pole detector filter to 10 Hz, which is more suitable for seismic use,
changing the output opamp to a low noise type and increasing the time constant
of the high pass filter, along with several other small changes. NE seemed
to have used a circuit designed by Philips for wider bandwidth commercial
LVDT applications. I have also been working on other magnetic sensor systems
using the Philips NE5521 LVDT chip, including modified transformers, somewhat
like Sean's, some using ferrite components and lately, a capacitative system.
I have a full write up nearly finished.
Your full write up should be VERY interesting!!
Perhaps
the greatest curiosity item I wonder about their transformer part, is whether
its really a precision wound unit like mentioned as a (professional) necessity
as on other web sites? It appears to be much like other general looking
transformers. Without any access I'd guess its somewhat linearly wound
but no where near precision.
If you want to measure several
inches of movement and require a linear response, you may need a precision
linear winding. If you only want a few mm and the field of the sensor rod
can be sensed over a physically much larger sensor winding, you just need
the windings to stay in a fixed position. There will of course be thermal
expansion and changes of resistance with temperature, but these effects
are very small over the 10 Hz bandwidth and the 5 to 30 sec of the high
pass filter time constant.
Perhaps
the biggest thing I "seem" to see, is that Seans original LRDT transformers
are in likelyhood kind of a crude nonlinear wire wrapping; whereas, your
LVDT, is a painstaking relatively precision wire layered device.
With Sean's variable reluctance
transformer sensor, the magnetic circuit is defined by the position of
the flat iron armature plate and the iron polepieces. In a LVDT, the interaction
is between the position of a magnetised armature and the varying distance
it moves inside the sensor coil, so the coil needs to be quite uniformly
wound. For a description of an LVDT, see http://www.msiusa.com/schaevitz/pdf/lvdt/LVDT_Intro.pdf
It is not too difficult to make even windings, so long as you do not use
extremely fine wire, do not try to wind too fast, slow up right at the
end of each layer and, most importantly, use very thin paper, like cigarette
or tissue paper, for interleaving each layer. This makes it easy to spot
and correct any overwinding or incorrectly spaced turns. It also makes
winding easier and helps to prevent shorted turns in between layers. I
made two matched 40,000 turn precision differential transformer coils this
way, for measuring paramagnetic susceptibility. A very small plastic tube
makes a good wire guide. It is also possible to just layer wind two LVDT
secondaries end to end on a sensor tube and use a ferrite or powder iron
cored choke to provide the magnetic excitation. This avoids having to wind
a central primary magnetising section in between, or over the top of the
secondaries.
Yet.....according to Seans
website, his LRDT is sensitive to a incredible 0.1nm. I've
zero
experience but it makes me wonder further about coils themselves between
the two. It would
seem the LRDT is much simpler to make and more sensitive overall.
Coupled with the very high sensitivity
of Sean's transducer, the movement range is small, perhaps +/-0.5 mm in
a 2 mm total gap, and the output is only linear for a limited range around
the zero position. This is just fine for a feedback seismometer, where
you try to hold the armature position constant. The out of range signal
increases dramatically before saturating, which can be bad news if the
seismometer feedback system gets out of lock.
Seans reluctance sensor sounds like it could be used in a "S-G" also,
although one might have a devil of a time especially when any
kind of small height S-G feedback system, might influence the sensor.
Perhaps a fixed eddy current damping system might be workable,
if far enough away from the sensor itself.
All
this is leading up to the question of whether a fairly linear wound (but
not exactly precisely layered) coil "could" somewhat work simarily (with
less sensitivity) with the same general ferrite core type setup.
Such coils are rather scarce I'am sure.
If you have an E core transformer
type winding, the magnetic flux is linked strongly to the winding, so great
winding precision is not required, only a good physical stability. The
magnetic field interactions are controlled by the positions and separations
of the iron laminations, so these need to be firmly fixed. These E core
types can be either modified audio transformers similar to Sean's, ferrite
cup transformers with DIY windings, a linear differential reluctance system
of the magslip type, or two physically large coils pairs bridged by a ferrite
rod, like the NE type.
Just
some (unexperienced) thoughts. I think the Nuova item costs around
$103 US dollars (PCB and LVDT) plus whatever shipping/handling. Sometimes
I think that a homebrew LVDT with perhaps a Phillips or Analog IC (and
other parts) might be a cheaper alternative......but probably more costly
for any R&D overall.
The two Analogue Devices LVDT
chips have a relatively high noise floor and are not suitable for our use.
The Philips NE5521 device is about 1/3 the price and you can get right
down to the intrinsic opamp noise level.
The LX1358 Kit price is €
51.65 + Carriage. Looking up today's exchange rate, this is just US
$51.23 !! There will be a charge on your Credit Card for the currency
conversion and the exchange rate will be lower than the International Banking
Rate quoted. Air Mail packets are reasonably priced and may take 10 days
to arrive. Be warned that International Carriers may have a minimum charge
of near $50 for any packet! They seem to be only relatively reasonably
priced within the USA.
Am missing something here....whats the difference between a "air mail
packet", and a, "International Carriers"? Did Nuova offer the
distinction
when you got your LVDT? Airmail v/s "ground" (ship)?
With a
LX1358, I get ~7 nano metre resolution over a +/-6 mm accurately linear
range, with 65 mV / micron output. The output is 10% down at +/-12 mm and
20% down at +/-15 mm, since the ''out of range'' response is of the usual
S shape. This wide range was designed for Lehman type systems, but the
sensor will work equally well on simple pendulums.
Thats quite a large sensor mm/mv output! Thanks for all the "feedback"
info!
Take care, Meredith
Subject: Re: STM 8 (LVDT subject)
From: "Mauro Mariotti" mariotti@.........
Date: Sun, 17 Nov 2002 10:13:29 +0100
Hi Meredith,
the lx1358 circuit is exactly the same used in the lx922 with few=20
small variations.
The LX922 and LX1358 coils are the same.
I think that the coils are wound for the pourpose of the seismometer
and not re-used from an another application.
They are very large to make easier the assembly of the mechanic.
That squared hole keep easy the assembly of the nucleus that is
needed to insert for last when you assemble the mechanic components.
Regards
Mauro
----- Original Message -----=20
From: meredithlamb=20
To: psn-l@.................
Sent: Saturday, November 16, 2002 11:32 PM
Subject: Re: STM 8 (LVDT subject)
Hi Mauro and all,=20
Thanks for the notes. I see your reference to the LX922 &=20
LX1358 on the web: The obsolete LX922 seismometer in its=20
entirety, certainly was a large unit. Is the same LVDT coil and =
circuit=20
board used on such, the same as on the small pendulum LX1358=20
that you know of?=20
http://mariottim.interfree.it/doc13_e.htm=20
Yes, if you can, and want to, it would be interesting to see=20
just what they used in the LVDT squarish transformer/s inasfar=20
as whether its precision laid out, or more ~jumbo wound.=20
They are somewhat large, and I suspect they are salvaged=20
coils meant originally for another use....but I could always be=20
wrong. In a sense, even if they are not precision, it kind of=20
suggests that other transformers could work also.....but with=20
a reduced sensitivity compared to precision wound LVDT's=20
(but still very good overall).=20
=20
Mauro Mariotti wrote:=20
Hi All, I worked very much with this LVDT.It is based on the Phllips =
NE5521N phase comparator.I can supply you the schematic if needed.The =
cost of the unit is 50$ for the circuit and 50$ for the mechanic tobuild =
up a complete horizontal sensor like to S-G type.I never disassembled =
the LVDT coils to but I can do it I have some sparepart in my lab.
Hi Meredith,
the lx1358 circuit is exactly the same =
used in the=20
lx922 with few
small variations.
The LX922 and LX1358 coils are the=20
same.
I think that the coils are wound for =
the pourpose=20
of the seismometer
and not re-used from an another=20
application.
They are very large to make easier the =
assembly of=20
the mechanic.
That squared hole keep easy the =
assembly of the=20
nucleus that is
needed to insert for last when you =
assemble the=20
mechanic components.
Regards
Mauro
----- Original Message -----
From:=20
meredithlamb
Sent: Saturday, November 16, =
2002 11:32=20
PM
Subject: Re: STM 8 (LVDT =
subject)
Hi Mauro and all,=20
Thanks for the notes. I see your reference to the LX922 & =
LX1358 on the web: The obsolete LX922 seismometer in its=20
entirety, certainly was a large unit. Is the same LVDT coil =
and=20
circuit
board used on such, the same as on the small pendulum =
LX1358=20
that you know of?=20
http://mariottim.inter=
free.it/doc13_e.htm=20
Yes, if you can, and want to, it would be interesting to see =
just what=20
they used in the LVDT squarish transformer/s inasfar
as whether =
its=20
precision laid out, or more ~jumbo wound.
They are somewhat large, =
and I=20
suspect they are salvaged
coils meant originally for another =
use....but I=20
could always be
wrong. In a sense, even if they are not =
precision,=20
it kind of
suggests that other transformers could work =
also.....but with=20
a reduced sensitivity compared to precision wound LVDT's
(but =
still=20
very good overall).
=20
Mauro Mariotti wrote:=20
Hi All, I worked very much with this LVDT.It is based on the =
Phllips NE5521N=20
phase comparator.I can supply you the schematic if needed.The cost =
of the=20
unit is 50$ for the circuit and 50$ for the mechanic tobuild up a =
complete=20
horizontal sensor like to S-G type.I never disassembled the LVDT =
coils to=20
but I can do it I have some sparepart in my=20
lab.
Subject: Digital Analisys of Seismic Data
From: Cristian Haulica cristianhaulica@.......
Date: 17 Nov 2002 13:35:13 -0000
Hy..
My graduation project (at the Automatic and computer
inginering dept. of Technical Univetsity Iasi, Romania) is an
seismograph (Lehman type). If someone knows where I can find
(on web) some algorithms, code, or open code projects
(preferable in C,C++,VC) related to Automatic Analisis on
Seismic Data, please reply.
Thank You.
PS. My connection to this mailing list isn't so good, so i
couldn't download the archive files. My apologies if this
question has been alredy answered.
----
Home, no matter how far...
http://www.home.ro
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: STM 8 (LVDT subject)
From: ChrisAtUpw@.......
Date: Sun, 17 Nov 2002 09:39:17 EST
In a message dated 16/11/02, meredithlamb@............. writes:
> Sean's reluctance sensor sounds like it could be used in a "S-G" also,
> although one might have a devil of a time especially when any kind of small
> height S-G feedback system, might influence the sensor. Perhaps a fixed
> eddy current damping system might be workable, if far enough away from the
>
Hi Meredith,
Sean's system should be fine for a pendulum sensor, if a bit
elaborate. I would not expect there to be any problem over the physical size
of the sensor. The miniature transformers are 15 mm (~5/8") across the
windings and 19 mm (~3/4") across the jaws of the E. The usual method of
suspending the iron armature on a brass plate should provide quite adequate
magnetic isolation.
SG seismometers normally use active damping with a coil and a bar
magnet. This can, with advantage, be coupled directly to the seismic mass.
The 'true' SG systems (as opposed to damped pendulums) get much of their
sensitivity from damping the otherwise underdamped pendulum.
On the side issue of magnetic damping, the Wing shaped two face pole
magnets sold by www.wondermagnet.com are very effective indeed at providing
magnetic damping and size for size, are much more effective than single pole
magnets. The smaller damping plate is placed over the joint between the two
wings, where the field reverses.
> >> The LX1358 Kit price is E 51.65 + Carriage. At today's exchange rate, this
>> is just US $51.23. There will be a charge on your Credit Card for the
>> currency conversion and the exchange rate will be lower than the
>> International Banking Rate quoted. Air Mail packets are reasonably priced
>> and may take 10 days to arrive. Be warned that International Carriers may
>> have a minimum charge of near $50 for any packet! They seem to be only
>>
> Am missing something here....whats the difference between a "air mail
>
Air Mail goes through the normal Mail system of most countries, but
there are strict limits on the size and weight for letters, packets and
parcels and you have to insure seperately over certain values. By
International Carriers, I am referring to Fedex, Amtrak, DHL, TNT etc. which
handle heavier, industrial and urgent goods.
When the UK part of Measurement Specialities, Schaevitz's
distributors, folded a while back, Schaevitz offered to supply direct from
the USA, but mentioned 'carriage charges'. When I enquired, these turned out
to be over $40 on any item, no matter how small. Schaevitz seemed incapable
or unwilling to provide near normal distributor service over some months and
seemed to have the bizarre idea that their customers should happily foot the
excess bill, as well as suffering a delivery delay and increased currency and
import charges. You don't either keep or win customers that way, particularly
when there is strong local competiton.
Nuova Elettronica are a large Italian organisation producing a very
wide range of well designed Kits and probably have more product lines than
Heathkit ever had. They assume that the builder can recognise components and
can read. They provide adequate constructional documentation, but they do not
provide 'idiot's construction guides'.
The sensor coils used on the LX1358 are obviously new and are similar
to low wattage 1:1 mains isolation transformer windings. There are two coils
mounted side by side in a sealed nylon case, which is the usual EEC
construction for 'double insulated' transformers. The coils look to be well
wound, but because of the geometry of the system, the output linearity of the
sensor does not depend on the 'precision' of the winding, like in an LVDT. On
the cutaway construction photo in the Schaevitz introduction,
http://www.msiusa.com/schaevitz/pdf/lvdt/LVDT_Intro.pdf you may notice that
the fatter sensor windings on their LVDTs are also split up into a series of
short coil sections, on much the same principle. There is a nice java applet
demonstrating a LVDT operating at
http://www.rdpe.com/displacement/lvdt/lvdt-principles.htm
Regards,
Chris Chapman
In a message dated 16/11/02, meredithlamb@............. writes:
Sean's reluctance sensor sounds like it could be used in a "S-G" also, although one might have a devil of a time especially when any kind of small height S-G feedback system, might influence the sensor. Perhaps a fixed eddy current damping system might be workable, if far enough away from the sensor itself.
Hi Meredith,
Sean's system should be fine for a pendulum sensor, if a bit elaborate. I would not expect there to be any problem over the physical size of the sensor. The miniature transformers are 15 mm (~5/8") across the windings and 19 mm (~3/4") across the jaws of the E. The usual method of suspending the iron armature on a brass plate should provide quite adequate magnetic isolation.
SG seismometers normally use active damping with a coil and a bar magnet. This can, with advantage, be coupled directly to the seismic mass. The 'true' SG systems (as opposed to damped pendulums) get much of their sensitivity from damping the otherwise underdamped pendulum.
On the side issue of magnetic damping, the Wing shaped two face pole magnets sold by www.wondermagnet.com are very effective indeed at providing magnetic damping and size for size, are much more effective than single pole magnets. The smaller damping plate is placed over the joint between the two wings, where the field reverses.
The LX1358 Kit price is E 51.65 + Carriage. At today's exchange rate, this is just US $51.23. There will be a charge on your Credit Card for the currency conversion and the exchange rate will be lower than the International Banking Rate quoted. Air Mail packets are reasonably priced and may take 10 days to arrive. Be warned that International Carriers may have a minimum charge of near $50 for any packet! They seem to be only relatively reasonably priced within the USA.
Am missing something here....whats the difference between a "air mail packet", and a, "International Carriers"?
Air Mail goes through the normal Mail system of most countries, but there are strict limits on the size and weight for letters, packets and parcels and you have to insure seperately over certain values. By International Carriers, I am referring to Fedex, Amtrak, DHL, TNT etc. which handle heavier, industrial and urgent goods.
When the UK part of Measurement Specialities, Schaevitz's distributors, folded a while back, Schaevitz offered to supply direct from the USA, but mentioned 'carriage charges'. When I enquired, these turned out to be over $40 on any item, no matter how small. Schaevitz seemed incapable or unwilling to provide near normal distributor service over some months and seemed to have the bizarre idea that their customers should happily foot the excess bill, as well as suffering a delivery delay and increased currency and import charges. You don't either keep or win customers that way, particularly when there is strong local competiton.
Nuova Elettronica are a large Italian organisation producing a very wide range of well designed Kits and probably have more product lines than Heathkit ever had. They assume that the builder can recognise components and can read. They provide adequate constructional documentation, but they do not provide 'idiot's construction guides'.
The sensor coils used on the LX1358 are obviously new and are similar to low wattage 1:1 mains isolation transformer windings. There are two coils mounted side by side in a sealed nylon case, which is the usual EEC construction for 'double insulated' transformers. The coils look to be well wound, but because of the geometry of the system, the output linearity of the sensor does not depend on the 'precision' of the winding, like in an LVDT. On the cutaway construction photo in the Schaevitz introduction, http://www.msiusa.com/schaevitz/pdf/lvdt/LVDT_Intro.pdf you may notice that the fatter sensor windings on their LVDTs are also split up into a series of short coil sections, on much the same principle. There is a nice java applet demonstrating a LVDT operating at http://www.rdpe.com/displacement/lvdt/lvdt-principles.htm
Regards,
Chris Chapman
Subject: Re: Digital Analisys of Seismic Data
From: "Mauro Mariotti" mariotti@.........
Date: Sun, 17 Nov 2002 20:06:53 +0100
"Automatic analisys of seismic data" is not so specific question.
Seismic data can be treated as a flow digitized analogic signal
with DSP tecniques. So any DSP guidebook can provides useful
information on the algorythms...
If you need more specific information you should post
more specific questions.
Regards
Mauro
----- Original Message -----
From: "Cristian Haulica"
To:
Sent: Sunday, November 17, 2002 2:35 PM
Subject: Digital Analisys of Seismic Data
>
>
> Hy..
>
> My graduation project (at the Automatic and computer
> inginering dept. of Technical Univetsity Iasi, Romania) is an
> seismograph (Lehman type). If someone knows where I can find
> (on web) some algorithms, code, or open code projects
> (preferable in C,C++,VC) related to Automatic Analisis on
> Seismic Data, please reply.
>
> Thank You.
>
> PS. My connection to this mailing list isn't so good, so i
> couldn't download the archive files. My apologies if this
> question has been alredy answered.
>
>
> ----
>
> Home, no matter how far...
> http://www.home.ro
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
>
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: STM 8 (LVDT subject)
From: meredithlamb meredithlamb@.............
Date: Mon, 18 Nov 2002 14:54:14 -0700
Hi Chris, and all,
ChrisAtUpw@....... wrote:
> In a message dated 16/11/02, meredithlamb@............. writes:
>
>
>> Sean's reluctance sensor sounds like it could be used in a "S-G"
>> also, although one might have a devil of a time especially when any
>> kind of small height S-G feedback system, might influence the
>> sensor. Perhaps a fixed eddy current damping system might be
>> workable, if far enough away from the sensor itself.
>
>
> Hi Meredith,
>
> Sean's system should be fine for a pendulum sensor, if a bit
> elaborate. I would not expect there to be any problem over the
> physical size of the sensor. The miniature transformers are 15 mm
> (~5/8") across the windings and 19 mm (~3/4") across the jaws of the
> E. The usual method of suspending the iron armature on a brass plate
> should provide quite adequate magnetic isolation.
Your statement of "a bit elaborate" for the Sean circuit is quite true
to me (ha), by comparison, a general LVDT circuit indeed looks
alot simplier. I see they've been around for over a hundred years
(in esscense). Perhaps in general, they could be the better more
sensitive and cheaper future for amateur seismology. Most U.S.,
companies truely want a "mint" for their LVDT coil items, which
seems to be the main current problem overall in that commercial
part approach.
> SG seismometers normally use active damping with a coil and a bar
> magnet. This can, with advantage, be coupled directly to the seismic
> mass. The 'true' SG systems (as opposed to damped pendulums) get much
> of their sensitivity from damping the otherwise underdamped pendulum.
>
> On the side issue of magnetic damping, the Wing shaped two face pole
> magnets sold by www.wondermagnet.com are very effective indeed at
> providing magnetic damping and size for size, are much more effective
> than single pole magnets. The smaller damping plate is placed over the
> joint between the two wings, where the field reverses.
Very true on the "wing" or 4 pole magnets. I'am rather
surprised more amateurs are not using this cheaper and more
effective damping (and even coil sensor pickup) route. Perhaps
(?), to be fair in that regard, its usually the larger the neodymium
magnet/s, the better the results. Most neodymium magnets are
rather small, whereas alot of the Alnico magnets are larger poled
but with alot less "potential" maximum gauss interaction. On the
other hand, two, "wing" magnets facing (attracting to each
other), can enhance results moreso.
>> > The LX1358 Kit price is E 51.65 + Carriage. At today's exchange
>> > rate, this is just US $51.23. There will be a charge on your Credit
>> > Card for the currency conversion and the exchange rate will be
>> > lower than the International Banking Rate quoted. Air Mail packets
>> > are reasonably priced and may take 10 days to arrive. Be warned
>> > that International Carriers may have a minimum charge of near $50
>> > for any packet! They seem to be only relatively reasonably priced
>> > within the USA.
>>
Most interesting on the cost. I'd guess the actual cost could be
~ double with the shipping charges added just for the LVDT and
circuit alone. Getting the mechanical S-G part added would
likely make it prohibitively alot more expensive.... ~ 2-4 times.
>> Am missing something here....whats the difference between a "air
>> mail packet", and a, "International Carriers"?
>
> Air Mail goes through the normal Mail system of most countries, but
> there are strict limits on the size and weight for letters, packets
> and parcels and you have to insure seperately over certain values. By
> International Carriers, I am referring to Fedex, Amtrak, DHL, TNT etc.
> which handle heavier, industrial and urgent goods.
Thanks for the info. Have shipped out to other countries before,
and sometimes the actual cost can even far exceed the value of the
item actually shipped. Its always quite expensive it seems.
> When the UK part of Measurement Specialities, Schaevitz's
> distributors, folded a while back, Schaevitz offered to supply direct
> from the USA, but mentioned 'carriage charges'. When I enquired, these
> turned out to be over $40 on any item, no matter how small. Schaevitz
> seemed incapable or unwilling to provide near normal distributor
> service over some months and seemed to have the bizarre idea that
> their customers should happily foot the excess bill, as well as
> suffering a delivery delay and increased currency and import charges.
> You don't either keep or win customers that way, particularly when
> there is strong local competiton.
True; alot of U.S. companies seem to go the same "self defeating"
route.
> Nuova Elettronica are a large Italian organisation producing a very
> wide range of well designed Kits and probably have more product lines
> than Heathkit ever had. They assume that the builder can recognise
> components and can read. They provide adequate constructional
> documentation, but they do not provide 'idiot's construction guides'.
Too bad they don't promote more of their items information via
the internet; but I think it might be related to a less hectic "way of
life" approach.
> The sensor coils used on the LX1358 are obviously new and are similar
> to low wattage 1:1 mains isolation transformer windings. There are two
> coils mounted side by side in a sealed nylon case, which is the usual
> EEC construction for 'double insulated' transformers. The coils look
> to be well wound, but because of the geometry of the system, the
> output linearity of the sensor does not depend on the 'precision' of
> the winding, like in an LVDT. On the cutaway construction photo in the
> Schaevitz introduction,
> http://www.msiusa.com/schaevitz/pdf/lvdt/LVDT_Intro.pdf you may
> notice that the fatter sensor windings on their LVDTs are also split
> up into a series of short coil sections, on much the same principle.
> There is a nice java applet demonstrating a LVDT operating at
> http://www.rdpe.com/displacement/lvdt/lvdt-principles.htm
Thanks for the info! Take care, Meredith Lamb
Hi Chris, and all,
ChrisAtUpw@....... wrote:
In a message
dated 16/11/02, meredithlamb@............. writes:
Sean's
reluctance sensor sounds like it could be used in a "S-G" also, although
one might have a devil of a time especially when any kind of small height
S-G feedback system, might influence the sensor. Perhaps a fixed eddy current
damping system might be workable, if far enough away from the sensor itself.
Hi Meredith,
Sean's system should be fine
for a pendulum sensor, if a bit elaborate. I would not expect there to
be any problem over the physical size of the sensor. The miniature
transformers are 15 mm (~5/8") across the windings and 19 mm (~3/4") across
the jaws of the E. The usual method of suspending the iron armature on
a brass plate should provide quite adequate magnetic isolation.
Your statement of "a bit elaborate" for the Sean circuit is quite true
to me (ha), by comparison, a general LVDT circuit indeed looks
alot simplier. I see they've been around for over a hundred years
(in esscense). Perhaps in general, they could be the better more
sensitive and cheaper future for amateur seismology. Most U.S.,
companies truely want a "mint" for their LVDT coil items, which
seems to be the main current problem overall in that commercial
part approach.
SG seismometers
normally use active damping with a coil and a bar magnet. This can,
with advantage, be coupled directly to the seismic mass. The 'true' SG
systems (as opposed to damped pendulums) get much of their sensitivity
from damping the otherwise underdamped pendulum.
On the side issue of magnetic
damping, the Wing shaped two face pole magnets sold by www.wondermagnet.com
are very effective indeed at providing magnetic damping and size for size,
are much more effective than single pole magnets. The smaller damping plate
is placed over the joint between the two wings, where the field reverses.
Very true on the "wing" or 4 pole magnets. I'am rather
surprised more amateurs are not using this cheaper and more
effective damping (and even coil sensor pickup) route. Perhaps
(?), to be fair in that regard, its usually the larger the neodymium
magnet/s, the better the results. Most neodymium magnets are
rather small, whereas alot of the Alnico magnets are larger poled
but with alot less "potential" maximum gauss interaction. On
the
other hand, two, "wing" magnets facing (attracting to each
other), can enhance results moreso.
The
LX1358 Kit price is E 51.65 + Carriage. At today's exchange rate, this
is just US $51.23. There will be a charge on your Credit Card for the currency
conversion and the exchange rate will be lower than the International Banking
Rate quoted. Air Mail packets are reasonably priced and may take 10 days
to arrive. Be warned that International Carriers may have a minimum charge
of near $50 for any packet! They seem to be only relatively reasonably
priced within the USA.
Most interesting on the cost. I'd guess the actual cost could be
~ double with the shipping charges added just for the LVDT and
circuit alone. Getting the mechanical S-G part added would
likely make it prohibitively alot more expensive.... ~ 2-4 times.
Am
missing something here....whats the difference between a "air mail packet",
and a, "International Carriers"?
Air Mail goes through the normal
Mail system of most countries, but there are strict limits on the size
and weight for letters, packets and parcels and you have to insure seperately
over certain values. By International Carriers, I am referring to Fedex,
Amtrak, DHL, TNT etc. which handle heavier, industrial and urgent goods.
Thanks for the info. Have shipped out to other countries before,
and sometimes the actual cost can even far exceed the value of the
item actually shipped. Its always quite expensive it seems.
When the
UK part of Measurement Specialities, Schaevitz's distributors, folded a
while back, Schaevitz offered to supply direct from the USA, but mentioned
'carriage charges'. When I enquired, these turned out to be over $40 on
any item, no matter how small. Schaevitz seemed incapable or unwilling
to provide near normal distributor service over some months and seemed
to have the bizarre idea that their customers should happily foot the excess
bill, as well as suffering a delivery delay and increased currency and
import charges. You don't either keep or win customers that way, particularly
when there is strong local competiton.
True; alot of U.S. companies seem to go the same "self defeating"
route.
Nuova
Elettronica are a large Italian organisation producing a very wide range
of well designed Kits and probably have more product lines than Heathkit
ever had. They assume that the builder can recognise components and can
read. They provide adequate constructional documentation, but they do not
provide 'idiot's construction guides'.
Too bad they don't promote more of their items information via
the internet; but I think it might be related to a less hectic "way
of
life" approach.
The sensor
coils used on the LX1358 are obviously new and are similar to low wattage
1:1 mains isolation transformer windings. There are two coils mounted side
by side in a sealed nylon case, which is the usual EEC construction for
'double insulated' transformers. The coils look to be well wound, but because
of the geometry of the system, the output linearity of the sensor does
not depend on the 'precision' of the winding, like in an LVDT. On the cutaway
construction photo in the Schaevitz introduction, http://www.msiusa.com/schaevitz/pdf/lvdt/LVDT_Intro.pdf
you may notice that the fatter sensor windings on their LVDTs are also
split up into a series of short coil sections, on much the same principle.
There is a nice java applet demonstrating a LVDT operating at http://www.rdpe.com/displacement/lvdt/lvdt-principles.htm
Thanks for the info! Take care, Meredith Lamb
Subject: Re: STM 8 (LVDT subject)
From: meredithlamb meredithlamb@.............
Date: Mon, 18 Nov 2002 14:54:57 -0700
Hi Mauro,
I'd now think you are correct, in the aspect of the LVDT coils
likely being made just for the seismo unit; just from the aspect
of the NE, being a large organization/company.
I do wonder what the size/diameter of the ferrite rod that
comes with the LVDT and circuit? Suspect its quite "loose"
clearance (~ 1-2 mm?) on any side. In the same sense, I
wonder what the dimension/s are of the transformer hole/s?
In ways, it seems possible that a tighter (larger) fitting ferrite
rod might enhance the sensitivity somewhat....but not likely
really needed at all.
Take care, Meredith Lamb
Mauro Mariotti wrote:
> Hi Meredith,the lx1358 circuit is exactly the same used in the lx922
> with fewsmall variations.The LX922 and LX1358 coils are the same.I
> think that the coils are wound for the pourpose of the seismometerand
> not re-used from an another application.They are very large to make
> easier the assembly of the mechanic.That squared hole keep easy the
> assembly of the nucleus that isneeded to insert for last when you
> assemble the mechanic components. RegardsMauro
Hi Mauro,
I'd now think you are correct, in the aspect of the LVDT coils
likely being made just for the seismo unit; just from the aspect
of the NE, being a large organization/company.
I do wonder what the size/diameter of the ferrite rod that
comes with the LVDT and circuit? Suspect its quite "loose"
clearance (~ 1-2 mm?) on any side. In the same sense, I
wonder what the dimension/s are of the transformer hole/s?
In ways, it seems possible that a tighter (larger) fitting ferrite
rod might enhance the sensitivity somewhat....but not likely
really needed at all.
Take care, Meredith Lamb
Mauro Mariotti wrote:
Hi Meredith,the
lx1358 circuit is exactly the same used in the lx922 with fewsmall variations.The
LX922 and LX1358 coils are the same.I think that the coils are wound for
the pourpose of the seismometerand not re-used from an another application.They
are very large to make easier the assembly of the mechanic.That squared
hole keep easy the assembly of the nucleus that isneeded to insert for
last when you assemble the mechanic components. RegardsMauro
Subject: Fw: Infrasonic sound
From: "Larry Cochrane" cochrane@..............
Date: Mon, 18 Nov 2002 17:03:39 -0800
----- Original Message -----
From: "Lewis,Bob"
To:
Sent: Monday, November 18, 2002 5:03 AM
Subject: Infrasonic sound
> Larry: Please post this for me....
>
> Bob Lewis
> Plano, Texas
>
> This morning, a little after midnight Dallas time, I heard (or rather
felt)
> what seemed like
> an 8-10 Hz. sine wave. It lasted about 40 seconds, long enough for me to
go
> out into
> the back yard and try to figure out where it was coming from. It was not
> sharp or
> staccato, sounded like a clean sine wave. My seismometer, of course was
off
> at the
> time, but this seemed airborne rather than through the earth. I could not
> determine any
> direction; seemed to be coming from all around. Does any one have any
ideas
> as to
> what this may have been ??
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Fw: Infrasonic sound
From: meredithlamb meredithlamb@.............
Date: Tue, 19 Nov 2002 01:53:19 -0700
Hi Bob,
???? perhaps its "somewhat" related to the "Taos hum". This
pneumonia has been "sensed" world wide, but most promently
in the US and the UK according to this website:
http://www.eskimo.com/~bilb/hum/hum.html
Am sure a web search engine, probably has alot of references
to the "Taos hum", and probably other "title" descriptions
and theories.
Take care, Meredith
> ----- Original Message -----
> From: "Lewis,Bob"
> To:
> Sent: Monday, November 18, 2002 5:03 AM
> Subject: Infrasonic sound
>
> > Larry: Please post this for me....
> >
> > Bob Lewis
> > Plano, Texas
> >
> > This morning, a little after midnight Dallas time, I heard (or rather
> felt)
> > what seemed like
> > an 8-10 Hz. sine wave. It lasted about 40 seconds, long enough for me to
> go
> > out into
> > the back yard and try to figure out where it was coming from. It was not
> > sharp or
> > staccato, sounded like a clean sine wave. My seismometer, of course was
> off
> > at the
> > time, but this seemed airborne rather than through the earth. I could not
> > determine any
> > direction; seemed to be coming from all around. Does any one have any
> ideas
> > as to
> > what this may have been ??
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Fw: Infrasonic sound
From: "Larry Cochrane" cochrane@..............
Date: Tue, 19 Nov 2002 01:16:40 -0800
Meredith,
The link below doesn't work, but as a Monty Python fan I love the file not
found message:
The file is deceased.
It is no longer. It has passed on.
You can not have that file in this life!
The file is dead, lifeless, departed, demised, late, extinct, no more.
It has broken on through to the other side.
I need to see if I can modify my web server to display this message and a
image of a Parrot with it's feet up in the air....
-Larry Cochrane
Redwood City, PSN
----- Original Message -----
From: "meredithlamb"
To:
Sent: Tuesday, November 19, 2002 12:53 AM
Subject: Re: Fw: Infrasonic sound
> Hi Bob,
>
> ???? perhaps its "somewhat" related to the "Taos hum". This
> pneumonia has been "sensed" world wide, but most promently
> in the US and the UK according to this website:
>
> http://www.eskimo.com/~bilb/hum/hum.html
>
> Am sure a web search engine, probably has alot of references
> to the "Taos hum", and probably other "title" descriptions
> and theories.
>
> Take care, Meredith
>
>
>
> > ----- Original Message -----
> > From: "Lewis,Bob"
> > To:
> > Sent: Monday, November 18, 2002 5:03 AM
> > Subject: Infrasonic sound
> >
> > > Larry: Please post this for me....
> > >
> > > Bob Lewis
> > > Plano, Texas
> > >
> > > This morning, a little after midnight Dallas time, I heard (or rather
> > felt)
> > > what seemed like
> > > an 8-10 Hz. sine wave. It lasted about 40 seconds, long enough for me
to
> > go
> > > out into
> > > the back yard and try to figure out where it was coming from. It was
not
> > > sharp or
> > > staccato, sounded like a clean sine wave. My seismometer, of course
was
> > off
> > > at the
> > > time, but this seemed airborne rather than through the earth. I could
not
> > > determine any
> > > direction; seemed to be coming from all around. Does any one have any
> > ideas
> > > as to
> > > what this may have been ??
> >
> > __________________________________________________________
> >
> > Public Seismic Network Mailing List (PSN-L)
> >
> > To leave this list email PSN-L-REQUEST@.............. with
> > the body of the message (first line only): unsubscribe
> > See http://www.seismicnet.com/maillist.html for more information.
>
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Fw: Infrasonic sound
From: meredithlamb meredithlamb@.............
Date: Tue, 19 Nov 2002 02:50:38 -0700
Hi Larry,
OK on the humor, its probably appropriate for the "wee hours"
(presume you're watching the Leonids meteor shower?) there
.....ha. I've only seen one out of the right direction, but 3 other
meteors from other directions. No great "meteor show" yet in
Denver at 2am. Ho-hUM....(excuse me...ha)
Think the address is correct, however, I saw what you got
once also, but it was addressed as:
http://www.eskimo.com/notfound.html
Perhaps a server problem, or, gosh knows?
Take care, Meredith
Larry Cochrane wrote:
> Meredith,
>
> The link below doesn't work, but as a Monty Python fan I love the file not
> found message:
>
> The file is deceased.
> It is no longer. It has passed on.
> You can not have that file in this life!
> The file is dead, lifeless, departed, demised, late, extinct, no more.
> It has broken on through to the other side.
>
> I need to see if I can modify my web server to display this message and a
> image of a Parrot with it's feet up in the air....
>
> -Larry Cochrane
> Redwood City, PSN
>
> ----- Original Message -----
> From: "meredithlamb"
> To:
> Sent: Tuesday, November 19, 2002 12:53 AM
> Subject: Re: Fw: Infrasonic sound
>
> > Hi Bob,
> >
> > ???? perhaps its "somewhat" related to the "Taos hum". This
> > pneumonia has been "sensed" world wide, but most promently
> > in the US and the UK according to this website:
> >
> > http://www.eskimo.com/~bilb/hum/hum.html
> >
> > Am sure a web search engine, probably has alot of references
> > to the "Taos hum", and probably other "title" descriptions
> > and theories.
> >
> > Take care, Meredith
> >
> >
> >
> > > ----- Original Message -----
> > > From: "Lewis,Bob"
> > > To:
> > > Sent: Monday, November 18, 2002 5:03 AM
> > > Subject: Infrasonic sound
> > >
> > > > Larry: Please post this for me....
> > > >
> > > > Bob Lewis
> > > > Plano, Texas
> > > >
> > > > This morning, a little after midnight Dallas time, I heard (or rather
> > > felt)
> > > > what seemed like
> > > > an 8-10 Hz. sine wave. It lasted about 40 seconds, long enough for me
> to
> > > go
> > > > out into
> > > > the back yard and try to figure out where it was coming from. It was
> not
> > > > sharp or
> > > > staccato, sounded like a clean sine wave. My seismometer, of course
> was
> > > off
> > > > at the
> > > > time, but this seemed airborne rather than through the earth. I could
> not
> > > > determine any
> > > > direction; seemed to be coming from all around. Does any one have any
> > > ideas
> > > > as to
> > > > what this may have been ??
> > >
> > > __________________________________________________________
> > >
> > > Public Seismic Network Mailing List (PSN-L)
> > >
> > > To leave this list email PSN-L-REQUEST@.............. with
> > > the body of the message (first line only): unsubscribe
> > > See http://www.seismicnet.com/maillist.html for more information.
> >
> >
> > __________________________________________________________
> >
> > Public Seismic Network Mailing List (PSN-L)
> >
> > To leave this list email PSN-L-REQUEST@.............. with
> > the body of the message (first line only): unsubscribe
> > See http://www.seismicnet.com/maillist.html for more information.
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: hum....another better hum reference...
From: meredithlamb meredithlamb@.............
Date: Tue, 19 Nov 2002 03:07:44 -0700
Hi Bob and Larry,
OK, this web site looks more through, with text, map, and
even a audio recording link (.wav) at the bottom. The wav
file/s takes quite awhile to load/play...and its "sounds"
similar to your description Bob. Their is even previous
reports places in Texas...I'am not sure where Plano, Texas
is right off. See:
http://www.crystalinks.com/taoshum.html
hum.....meredith
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Fw: Infrasonic sound
From: ian@...........
Date: Tue, 19 Nov 2002 10:43:55 +0000 (GMT)
Translated: the hum has stopped!
Quoting Larry Cochrane :
> Meredith,
>
> The link below doesn't work, but as a Monty Python fan I love the file
> not
> found message:
>
> The file is deceased.
> It is no longer. It has passed on.
> You can not have that file in this life!
> The file is dead, lifeless, departed, demised, late, extinct, no more.
> It has broken on through to the other side.
>
> I need to see if I can modify my web server to display this message and
> a
> image of a Parrot with it's feet up in the air....
>
> -Larry Cochrane
> Redwood City, PSN
>
> ----- Original Message -----
> From: "meredithlamb"
> To:
> Sent: Tuesday, November 19, 2002 12:53 AM
> Subject: Re: Fw: Infrasonic sound
>
>
> > Hi Bob,
> >
> > ???? perhaps its "somewhat" related to the "Taos hum". This
> > pneumonia has been "sensed" world wide, but most promently
> > in the US and the UK according to this website:
> >
> > http://www.eskimo.com/~bilb/hum/hum.html
> >
> > Am sure a web search engine, probably has alot of references
> > to the "Taos hum", and probably other "title" descriptions
> > and theories.
> >
> > Take care, Meredith
> >
> >
> >
> > > ----- Original Message -----
> > > From: "Lewis,Bob"
> > > To:
> > > Sent: Monday, November 18, 2002 5:03 AM
> > > Subject: Infrasonic sound
> > >
> > > > Larry: Please post this for me....
> > > >
> > > > Bob Lewis
> > > > Plano, Texas
> > > >
> > > > This morning, a little after midnight Dallas time, I heard (or
> rather
> > > felt)
> > > > what seemed like
> > > > an 8-10 Hz. sine wave. It lasted about 40 seconds, long enough
> for me
> to
> > > go
> > > > out into
> > > > the back yard and try to figure out where it was coming from. It
> was
> not
> > > > sharp or
> > > > staccato, sounded like a clean sine wave. My seismometer, of
> course
> was
> > > off
> > > > at the
> > > > time, but this seemed airborne rather than through the earth. I
> could
> not
> > > > determine any
> > > > direction; seemed to be coming from all around. Does any one have
> any
> > > ideas
> > > > as to
> > > > what this may have been ??
> > >
> > > __________________________________________________________
> > >
> > > Public Seismic Network Mailing List (PSN-L)
> > >
> > > To leave this list email PSN-L-REQUEST@.............. with
> > > the body of the message (first line only): unsubscribe
> > > See http://www.seismicnet.com/maillist.html for more information.
> >
> >
> > __________________________________________________________
> >
> > Public Seismic Network Mailing List (PSN-L)
> >
> > To leave this list email PSN-L-REQUEST@.............. with
> > the body of the message (first line only): unsubscribe
> > See http://www.seismicnet.com/maillist.html for more information.
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
>
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: stability of a Lehman
From: "Charles R. Patton" charles.r.patton@........
Date: Tue, 19 Nov 2002 09:00:12 -0800
There have been numerous discussions about lengthening the period of a
Lehman beyond the approximately 10 sec period and it becomes
"unstable."
The question is - unstable in what way? The period changes, the
centering fails, sensitivity goes haywire? In particular, if the answer
is, "The centering fails," does the center just move around, or does the
beam "flop" to one side or the other?
I'm doing some thought experiments during my long commute, and I'm
thinking about the sources of error. In particular it's been mentioned
before that the center of rotation changes on the flexible hinge
designs. That's intuitive, but how much and in what direction - toward
stability or instability? Has anybody figured out the actual path of the
center of rotation for a typical Lehman? Crossed-X flex hinges were
mentioned, but in this application with side force, I don't think they
would be any less susceptible to the same de-centering.
Another question is the upright's rigidity. Several pounds of weight at
the end of a boom is a fair torque moment which is resisted by the
spring constant of the 'pipe' (in the pipe constructed versions)
vertical. How much does this constant vary with temperature in standard
steel?
Anyway, if there is an answer I should have looked up in the past posts,
just flame me, but please include an approximate date and subject header
I can go looking for!
Thanks,
Charles R. Patton
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: stability of a Lehman
From: "Larry Cochrane" cochrane@..............
Date: Tue, 19 Nov 2002 16:18:09 -0800
Charles,
Long period sensors like a Lehman are sensitive to ground tilt. The longer
the period the more sensitive it is to tilt changes. What happens is the
boom wonders around when the tilt of the ground changes. The changing of the
position of the boom effects the sensitivity since the distance between the
magnet and pickup coil changes over time.
My Lehman has even more of a problem because it is sitting on a wood floor.
Whenever the humidity changes I need to re adjust the sensor. At this point
I have given up on my Lehman do to this problem. I just don't have the time
to constantly monitor the sensor. To record teleseismic events I use my SG
sensor and for local events either a geophone or accelerometer.
Regards,
Larry Cochrane
Redwood City, PSN
----- Original Message -----
From: "Charles R. Patton"
To:
Sent: Tuesday, November 19, 2002 9:00 AM
Subject: stability of a Lehman
> There have been numerous discussions about lengthening the period of a
> Lehman beyond the approximately 10 sec period and it becomes
> "unstable."
>
> The question is - unstable in what way? The period changes, the
> centering fails, sensitivity goes haywire? In particular, if the answer
> is, "The centering fails," does the center just move around, or does the
> beam "flop" to one side or the other?
>
> I'm doing some thought experiments during my long commute, and I'm
> thinking about the sources of error. In particular it's been mentioned
> before that the center of rotation changes on the flexible hinge
> designs. That's intuitive, but how much and in what direction - toward
> stability or instability? Has anybody figured out the actual path of the
> center of rotation for a typical Lehman? Crossed-X flex hinges were
> mentioned, but in this application with side force, I don't think they
> would be any less susceptible to the same de-centering.
>
> Another question is the upright's rigidity. Several pounds of weight at
> the end of a boom is a fair torque moment which is resisted by the
> spring constant of the 'pipe' (in the pipe constructed versions)
> vertical. How much does this constant vary with temperature in standard
> steel?
>
> Anyway, if there is an answer I should have looked up in the past posts,
> just flame me, but please include an approximate date and subject header
> I can go looking for!
>
> Thanks,
> Charles R. Patton
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Help with self leveling Lehman
From: "Dewayne Hill" n0ssy@.........
Date: Tue, 19 Nov 2002 19:03:50 -0700
I want to make my Lehman self leveling as it is in the crawl space and =
I'm getting to the age I hate
crawling on my hands and knees as I did when I was 3.
What I have in mind, but need help with is to connect a common wire to =
the base plate which in turn
will also put the same electrical potential on the boom as my Lehman is =
all metal. I want to insulate
my boom stops from the base plate and connect a plus voltage to it and a =
minus voltage to the other
stop. When the boom touches one of the stops it will complete a circuit =
that will activate a DC motor that
in turn will driver one of my leveling screws a preset amount of =
rotations or for X amount of time.
What I need help with is a circuit to control the motor. I have read =
that a step motor can have a controller
that will control the number of rotations or steps and then stop.
Can anyone Help?
Regards,
Dewayne Hill=20
I want to make my Lehman self leveling as it is in the crawl space =
and I'm=20
getting to the age I hate
crawling on my hands and knees as I did when I was 3.
What I have in mind, but need help with is to connect a common wire =
to the=20
base plate which in turn
will also put the same electrical potential on the boom as my Lehman =
is all=20
metal. I want to insulate
my boom stops from the base plate and connect a plus voltage to it =
and a=20
minus voltage to the other
stop. When the boom touches one of the stops it will complete a =
circuit that=20
will activate a DC motor that
in turn will driver one of my leveling screws a preset amount of =
rotations or=20
for X amount of time.
What I need help with is a circuit to control the motor. I have read =
that a=20
step motor can have a controller
that will control the number of rotations or steps and then stop.
Can anyone Help?
Regards,
Dewayne Hill
Subject: Help with self leveling Lehman
From: Kplblange@.......
Date: Tue, 19 Nov 2002 21:52:41 EST
I am not sending you any suggestions except to say that what you wish to
do can be done but it will be very involved and you will need to crawl in the
get it to work. I had a Lehman working some years ago and know what a time
it is to have it stay in neutral. I wonder if I should have make a vertical
one and have plans in an old Scientific American. The problem is that it
needs springs that best would be make by a machine shop. They are not coil
springs but flat pieces of metal.
Ken from Gardena, CA
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Want a drum recorder
From: Kplblange@.......
Date: Tue, 19 Nov 2002 22:01:39 EST
I do not wish to go to digital for several reason. I have the Lehman and
used it for several years with a strip-chart recorder. The cost of ink and
paper became prohibitive and I turned it off.
I want to find a drum recorder and have had no success in finding a
source. Can anyone help me? I can repair it bother mechanically and
electrically. I think the seismic labs are phasing them out and I wonder
where they are going.
Ken in Gardena, CA
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Help with self leveling Lehman
From: Thomas W Leiper twleiper@........
Date: Wed, 20 Nov 2002 00:54:38 -0500
Why don't you put a tank (half filled) of water on each side of the
Lehman
and use two little aquarium pumps to pump the water back and forth
between
them, thus shifting the floor slightly. You could then adjust the flow
rate with
a throttle valve to get the desired hysterisis, since you would want it
to pump
more water than that which was simply required to move off the "stops".
Each
one simply pumps from the bottom into the top of the other. A pair of
chemical
tanks for water conditioners would be cheap, have tight-fitting lids to
eliminate
evaporation, and, at 15 gal would weigh up to 120 lbs, which should be
more
than enough to do the job. No fancy circuitry, machining or vibrations to
deal with.
In addition, they would guard your sensitive detector from stray cosmic
rays.
Tom
On Tue, 19 Nov 2002 19:03:50 -0700 "Dewayne Hill"
writes:
I want to make my Lehman self leveling as it is in the crawl space and
I'm getting to the age I hate
crawling on my hands and knees as I did when I was 3.
What I have in mind, but need help with is to connect a common wire to
the base plate which in turn
will also put the same electrical potential on the boom as my Lehman is
all metal. I want to insulate
my boom stops from the base plate and connect a plus voltage to it and a
minus voltage to the other
stop. When the boom touches one of the stops it will complete a circuit
that will activate a DC motor that
in turn will driver one of my leveling screws a preset amount of
rotations or for X amount of time.
What I need help with is a circuit to control the motor. I have read that
a step motor can have a controller
that will control the number of rotations or steps and then stop.
Can anyone Help?
Regards,
Dewayne Hill
Why don't you put a tank (half filled) of water on each side of the=20
Lehman
and use two little aquarium pumps to pump the water back and forth=20
between
them, thus shifting the floor slightly. You could then adjust the flow=
rate=20
with
a throttle valve to get the desired hysterisis, since you would want =
it to=20
pump
more water than that which was simply required to move off the "stops"=
..=20
Each
one simply pumps from the bottom into the top of the other. A pair of=
=20
chemical
tanks for water conditioners would be cheap, have tight-fitting lids =
to=20
eliminate
evaporation, and, at 15 gal would weigh up to 120 lbs, which should be=
=20
more
than enough to do the job. No fancy circuitry, machining or =
vibrations=20
to deal with.
In addition, they would guard your sensitive detector from stray =
cosmic=20
rays.
Tom
On Tue, 19 Nov 2002 19:03:50 -0700 "Dewayne Hill" <
n0ssy@.........> writes:
I want to make my Lehman self leveling as it is in the crawl space and=
I'm=20
getting to the age I hate
crawling on my hands and knees as I did when I was 3.
What I have in mind, but need help with is to connect a common wire to=
the=20
base plate which in turn
will also put the same electrical potential on the boom as my Lehman =
is all=20
metal. I want to insulate
my boom stops from the base plate and connect a plus voltage to it and=
a=20
minus voltage to the other
stop. When the boom touches one of the stops it will complete a =
circuit=20
that will activate a DC motor that
in turn will driver one of my leveling screws a preset amount of =
rotations=20
or for X amount of time.
What I need help with is a circuit to control the motor. I have read =
that a=20
step motor can have a controller
that will control the number of rotations or steps and then stop.
Can anyone Help?
Regards,
Dewayne Hill
Subject: Re: Want a drum recorder
From: Thomas W Leiper twleiper@........
Date: Wed, 20 Nov 2002 00:57:39 -0500
You might think about the strip recorder I made that uses
adding machine paper and Scripto pens. Photos and a
brief description are in my arcticle "Nice little seismo..."
on the PSN Redwood City Web page.
Tom
On Tue, 19 Nov 2002 22:01:39 EST Kplblange@....... writes:
> I do not wish to go to digital for several reason. I have the
> Lehman and
> used it for several years with a strip-chart recorder. The cost of
> ink and
> paper became prohibitive and I turned it off.
> I want to find a drum recorder and have had no success in
> finding a
> source. Can anyone help me? I can repair it bother mechanically and
>
> electrically. I think the seismic labs are phasing them out and I
> wonder
> where they are going.
>
> Ken in Gardena, CA
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
>
>
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Help with self leveling Lehman
From: meredithlamb meredithlamb@.............
Date: Tue, 19 Nov 2002 23:08:30 -0700
Hi Dewayne,
Ramsey Electronics "might" have what you want/need. They
list a Stepper Motor Driver, and a DC Motor Speed Control,
kit/s. They look to be complete, and I'd guess with minimum
circuitry. One can also buy a chassis for the specific kit/s.
http://www.ramseykits.com
Click on Hobby Kits, and use the search there. I've not
bought anything from them, so I can't really recommend them,
but, they've been in business some 30 odd years or so. Their
items would have to match up with what you have now, or,
are comtemplating getting.
Perhaps the bigger problem is just the motor and/or gears
to be driven with? One would likely need a "harder to find" DC
motor with a "high" gear speed reduction ratio attachment to
where it can be somewhat controlled/limited. One might connect
it all up, and simply drive a on/off switch while watching your
SDR monitor I suppose.
I'd think it would be rather very difficult to mechanically match it
all up well. The motor activation itself might create so much sensor
coil pickup noise from vibration, that the total effort/cost might all
be counterproductive.
If I vaguely remember (?), your unit/s sit on concrete pavers
on bare soil? If so... the best (and strenuious) next thing is to
actually make a solid concrete pier and house/insulate it. If
its moderately well done, the number of adjustment trips should
drop considerably. I had the same problem as you, but the
vault/pier approach really helped alot here. The bigger the pier
the less the ground water tilt overall. Insulation is also a must,
the temperature effects do contribute to the metals expansion
and contractions of the seismo/s.
Take care, Meredith
Dewayne Hill wrote:
> I want to make my Lehman self leveling as it is in the crawl space and
> I'm getting to the age I hate
>
> crawling on my hands and knees as I did when I was 3.
>
> What I have in mind, but need help with is to connect a common wire to
> the base plate which in turn
>
> will also put the same electrical potential on the boom as my Lehman
> is all metal. I want to insulate
>
> my boom stops from the base plate and connect a plus voltage to it and
> a minus voltage to the other
>
> stop. When the boom touches one of the stops it will complete a
> circuit that will activate a DC motor that
>
> in turn will driver one of my leveling screws a preset amount of
> rotations or for X amount of time.
>
> What I need help with is a circuit to control the motor. I have read
> that a step motor can have a controller
>
> that will control the number of rotations or steps and then stop.
>
> Can anyone Help?
>
> Regards,
>
> Dewayne Hill
Hi Dewayne,
Ramsey Electronics "might" have what you want/need. They
list a Stepper Motor Driver, and a DC Motor Speed Control,
kit/s. They look to be complete, and I'd guess with minimum
circuitry. One can also buy a chassis for the specific kit/s.
http://www.ramseykits.com
Click on Hobby Kits, and use the search there. I've not
bought anything from them, so I can't really recommend them,
but, they've been in business some 30 odd years or so. Their
items would have to match up with what you have now, or,
are comtemplating getting.
Perhaps the bigger problem is just the motor and/or gears
to be driven with? One would likely need a "harder to find" DC
motor with a "high" gear speed reduction ratio attachment to
where it can be somewhat controlled/limited. One might connect
it all up, and simply drive a on/off switch while watching your
SDR monitor I suppose.
I'd think it would be rather very difficult to mechanically match it
all up well. The motor activation itself might create so much
sensor
coil pickup noise from vibration, that the total effort/cost might
all
be counterproductive.
If I vaguely remember (?), your unit/s sit on concrete pavers
on bare soil? If so... the best (and strenuious) next thing is
to
actually make a solid concrete pier and house/insulate it. If
its moderately well done, the number of adjustment trips should
drop considerably. I had the same problem as you, but the
vault/pier approach really helped alot here. The bigger the pier
the less the ground water tilt overall. Insulation is also a
must,
the temperature effects do contribute to the metals expansion
and contractions of the seismo/s.
Take care, Meredith
Dewayne Hill wrote:
I want to make my Lehman
self leveling as it is in the crawl space and I'm getting to the age I
hate
crawling on my hands and knees as I did when I was 3.
What I have in mind, but need help with is to connect
a common wire to the base plate which in turn
will also put the same electrical potential on the boom
as my Lehman is all metal. I want to insulate
my boom stops from the base plate and connect a plus voltage
to it and a minus voltage to the other
stop. When the boom touches one of the stops it will complete
a circuit that will activate a DC motor that
in turn will driver one of my leveling screws a preset
amount of rotations or for X amount of time.
What I need help with is a circuit to control the motor.
I have read that a step motor can have a controller
that will control the number of rotations or steps and
then stop.
Can anyone Help?
Regards,
Dewayne Hill
Subject: Re: Help with self leveling Lehman (vertical spring thought)
From: meredithlamb meredithlamb@.............
Date: Tue, 19 Nov 2002 23:25:22 -0700
Hi Ken,
Perhaps a hacksaw blade/s might work (?) for your unspecified
size flat spring material? I've read of some email mention
in the past with such, but never tried it. Its not the
best "spring" material, as it can be bent, but it can bend
within some mechanical constraints and not get damaged.
Even real spring material has its bending limits.
Take care, Meredith
Kplblange@....... wrote:
> (Previous Clipped) I wonder if I should have make a vertical
> one and have plans in an old Scientific American. The problem is that it
> needs springs that best would be make by a machine shop. They are not coil
> springs but flat pieces of metal.
>
> Ken from Gardena, CA>
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Help with self leveling Lehman
From: "Larry Cochrane" cochrane@..............
Date: Tue, 19 Nov 2002 22:27:42 -0800
Meredith wrote:
"Perhaps the bigger problem is just the motor and/or gears
to be driven with? One would likely need a "harder to find" DC
motor with a "high" gear speed reduction ratio attachment to
where it can be somewhat controlled/limited."
Jameco Electronics (www.jameco.com) has a reversible DC motor that has a
speed of ~2 RPM. It as a 3000 to 1 gear head that is perfect for adjusting
sensors. I use one on my SG sensor so I don't have to lift off the box to
get to the leveling screw. The Jameco part number is 176049 and the cost is
$18.95. I manually adjust my sensor my temporarily connecting up a 9 volt
battery to the motor.
-Larry Cochrane
Redwood City, PSN
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Help with self leveling Lehman
From: meredithlamb meredithlamb@.............
Date: Wed, 20 Nov 2002 00:16:24 -0700
Hi all,
The "worst possible helpful reality resolution" (ha), to frequent
horizontal seismometer adjustments is to actually get down and
dirty and make a large/thick isolated ground pier out of concrete
and house it all with a surrounding insulated box/vault/building.
For the "physical work allergic" members....I'd suggest you
somehow get your wife, kids, (someone else) to do all the
digging, mixing of concrete (yea....sure!!...."you say"...ha).
Their will still be house influenced tilt when its made
underneath such; even in loose soil, but it should yield
considerably less need for set screw adjustments in the long term.
I'd even suggest that the pier be made over thick insulation
pliable plastic sheet/s, to keep the ground moisture/water
out of the concrete pier itself. A surrounding covering "vault"
thats well insulated will also help somewhat. I used to use
concrete patio squares on loose dirt and that required
several adjustments a week (for a horizontal). With the
present "vault" and pier, its now ~ once a month.
A vertical is not very influenced by "ground" tilt of course ......
but....they tend to be much more temperature sensitive, where a
coiled or flat spring is involved....hence adding ALOT of insulation
"R factor" is quite helpful. Without insulation and on a simple
dirt/concrete paver, I used to have to adjust it ~ once a day....
but with a insulated vault, its ~ every 6 months or so.
Take care, Meredith
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Help with self leveling Lehman
From: ian@...........
Date: Wed, 20 Nov 2002 09:23:25 +0000 (GMT)
a few dimensions would help, width, length and depth of the peer. I hope to be
making one in the next 6 months. Does the peer have to be the same size as the
platform it supports all the way down or can it have a small circular cross
section?
TIA
Ian Smith
Quoting meredithlamb :
> Hi all,
>
> The "worst possible helpful reality resolution" (ha), to frequent
> horizontal seismometer adjustments is to actually get down and
> dirty and make a large/thick isolated ground pier out of concrete
> and house it all with a surrounding insulated box/vault/building.
>
> For the "physical work allergic" members....I'd suggest you
> somehow get your wife, kids, (someone else) to do all the
> digging, mixing of concrete (yea....sure!!...."you say"...ha).
>
> Their will still be house influenced tilt when its made
> underneath such; even in loose soil, but it should yield
> considerably less need for set screw adjustments in the long term.
>
> I'd even suggest that the pier be made over thick insulation
> pliable plastic sheet/s, to keep the ground moisture/water
> out of the concrete pier itself. A surrounding covering "vault"
> thats well insulated will also help somewhat. I used to use
> concrete patio squares on loose dirt and that required
> several adjustments a week (for a horizontal). With the
> present "vault" and pier, its now ~ once a month.
>
> A vertical is not very influenced by "ground" tilt of course ......
> but....they tend to be much more temperature sensitive, where a
> coiled or flat spring is involved....hence adding ALOT of insulation
> "R factor" is quite helpful. Without insulation and on a simple
> dirt/concrete paver, I used to have to adjust it ~ once a day....
> but with a insulated vault, its ~ every 6 months or so.
>
> Take care, Meredith
>
>
>
>
>
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
>
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: stability of a Lehman
From: "Frank Cooper" fxc@.......
Date: Wed, 20 Nov 2002 03:36:46 -0600
Hi Charles and other PSN members,
I think too much is being made of the "unstable" characteristics of the
Lehman. Both of mine (T Max and Old Lehman) are set up in my garage with a
sloping concrete floor. They are in the same garage with a washing machine
and drier with only about six or eight feet separating them from my ham
shack in a small garage room. They are next to the front garage door and
only about 20 feet from a busy street. A car and a van park only about six
feet from them. Foot traffic on the porch is several feet away. Here on
the Gulf Coast of Texas (near Houston) our houses are constructed with
concrete slabs resting on clay soil. All the houses in my subdivision have
constant problems with concrete slabs that shift with each rain or dry
period. Our sheet rock walls frequently crack and the wall corners shift
and open for this reason. My modified Lehman has been in constant operation
resting on my garage floor since January, 1997. After a heavy rain I have
learned to check the pendulum to see if it is centered. If it is not, it
only take me a few seconds to center it. I usually check it every night
before going to bed to see if it needs centering.
I have worked on my Old Lehman only once and that was to change the
pendulum. It was producing a period of only 12 seconds or so. It had a
pendulum with its end ground to a point that rested in a dimple of a steel
bolt head. 12 seconds seemed to be the limit. Then along came John Cole
with his ball bearing method. John lives only a few miles from me and he
presented me with a polished bolt and a pendulum with a ball bearing
inserted in one end. We changed the pendulum out to where the ball bearing
rested on the polished bolt. I was able to immediately increase the period
to about 18 seconds and after an adjustment or two the period has remained
over 20 seconds. John recently presented me with his T Max detector which
is a modified Lehman with a nickel chrome ball bearing resting upon a
slightly convex nickel chrome polished steel surface at the lower pivot
point. The upper suspension point has a nickel chrome ball bearing resting
on a slightly convex polished nickel chrome surface. The nickel chrome steel
convex surface is impervious to dimpling or scratching by the ball. The
period of this instrument remains at 27 to 30 seconds. It is difficult to
time the period exactly because the pendulum moves so slowly.
I checked the pendulum tonight and it is still centered from 24 hours ago.
If polishing a nickel chrome surface is too much trouble I suggest using the
ball bearing with a polished bolt at the lower pivot point and fine piano
wire at the upper suspension point. The Lehman is a simple instrument that
produces great results (especially with a ball bearing pivot point) but the
owner must devote a couple of minutes a day to keep the pendulum centered.
I do not try to upload all the quakes I detect to PSN but there are enough
posted for anyone to check how my simple sensors resting on a concrete
garage floor with much nearby traffic produces results.
Pictures and descriptions of my Lehman detectors are included in my web page
at http://pages.prodigy.net/fxc/
May you keep your pendulum centered,
Frank Cooper, Friendswood, Texas, USA
----- Original Message -----
From: Charles R. Patton
To:
Sent: Tuesday, November 19, 2002 11:00 AM
Subject: stability of a Lehman
> There have been numerous discussions about lengthening the period of a
> Lehman beyond the approximately 10 sec period and it becomes
> "unstable."
>
> The question is - unstable in what way? The period changes, the
> centering fails, sensitivity goes haywire? In particular, if the answer
> is, "The centering fails," does the center just move around, or does the
> beam "flop" to one side or the other?
>
> I'm doing some thought experiments during my long commute, and I'm
> thinking about the sources of error. In particular it's been mentioned
> before that the center of rotation changes on the flexible hinge
> designs. That's intuitive, but how much and in what direction - toward
> stability or instability? Has anybody figured out the actual path of the
> center of rotation for a typical Lehman? Crossed-X flex hinges were
> mentioned, but in this application with side force, I don't think they
> would be any less susceptible to the same de-centering.
>
> Another question is the upright's rigidity. Several pounds of weight at
> the end of a boom is a fair torque moment which is resisted by the
> spring constant of the 'pipe' (in the pipe constructed versions)
> vertical. How much does this constant vary with temperature in standard
> steel?
>
> Anyway, if there is an answer I should have looked up in the past posts,
> just flame me, but please include an approximate date and subject header
> I can go looking for!
>
> Thanks,
> Charles R. Patton
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSN-L)
>
> To leave this list email PSN-L-REQUEST@.............. with
> the body of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
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Public Seismic Network Mailing List (PSN-L)
Subject: Specific questions relative to \"Digital Digital Analisis of Seismic Data\"
From: Cristian Haulica cristianhaulica@.......
Date: 20 Nov 2002 10:46:22 -0000
As well said Mauro Mariotti, here are some specific
questions: I am interested in algorithms and open source
projects in: 1: The detection of P & S waves. 2: The
mathematical functions for: a: determining the distance to
epicenter from the time difference between P & S waves. b:
determining the magnitude of the earthquake. c: determining
the actual time of the begining of the earthquake (at the
epicenter). d: determining the magnitude at the epicenter.
etc. Note: I could found only graphics, dubious function ,
discrete values or inverse founctions (relative to what I
needed)
My project itends to get a minimum amounth of basical
earthquake data from a horisontal Lehman pendulum recordings.
Note that I am a Computer science student and seismology isn't
my strong point (yet ;) ).
If someone nows some sites where i can find such data please
reply.
Regards CristianH.
----
Home, no matter how far...
http://www.home.ro
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Public Seismic Network Mailing List (PSN-L)
Subject: Re: Want a drum recorder
From: CapAAVSO@.......
Date: Wed, 20 Nov 2002 09:37:47 EST
In a message dated 11/20/02 3:01:56 AM GMT Standard Time, Kplblange@.......
writes:
> I do not wish to go to digital for several reason. I have the Lehman and
>
> used it for several years with a strip-chart recorder. The cost of ink and
>
> paper became prohibitive and I turned it off.
> I want to find a drum recorder and have had no success in finding a
> source. Can anyone help me? I can repair it bother mechanically and
> electrically. I think the seismic labs are phasing them out and I wonder
> where they are going.
Hi Ken,
I have two Sprengnether drums brand new in the box, never been unpacked. You
can have one of these for $50 if you will pay the shipping charges. They are
packed in the original wooden crates by Sprengnether and ready to ship. They
are the top-of-the line Sprengnether drums only. You will have to mount a pen
motor on them and a pen. You can then scotch tape a piece of plain paper onto
the drum to make a classic analog seismogram. Alternatively you could run the
drum with photosensitive paper that Sprengnether designed them to use. The
manual and the optics and everything you need to do this is packed in the
crate with the drum. It consists of a beautiful very sensitive galvanometer
that reflects a light beam onto the photosensitive paper to draw the line.
The galvanometer is sensitive enough to record the seismic signal directly
from a seismometer without an amplifier. The output of your Lehman would
probably drive it without amplification.
Best regards,
Cap
(Casper Hossfield.......New Jersey)
In a message dated 11/20/02 3:01:56 AM GMT Standard Time, Kplblange@....... writes:
I do not wish to go to digital for several reason. I have the Lehman and
used it for several years with a strip-chart recorder. The cost of ink and
paper became prohibitive and I turned it off.
I want to find a drum recorder and have had no success in finding a
source. Can anyone help me? I can repair it bother mechanically and
electrically. I think the seismic labs are phasing them out and I wonder
where they are going
.
Hi Ken,
I have two Sprengnether drums brand new in the box, never been unpacked. You can have one of these for $50 if you will pay the shipping charges. They are packed in the original wooden crates by Sprengnether and ready to ship. They are the top-of-the line Sprengnether drums only. You will have to mount a pen motor on them and a pen. You can then scotch tape a piece of plain paper onto the drum to make a classic analog seismogram. Alternatively you could run the drum with photosensitive paper that Sprengnether designed them to use. The manual and the optics and everything you need to do this is packed in the crate with the drum. It consists of a beautiful very sensitive galvanometer that reflects a light beam onto the photosensitive paper to draw the line. The galvanometer is sensitive enough to record the seismic signal directly from a seismometer without an amplifier. The output of your Lehman would probably drive it without amplification.
Best regards,
Cap
(Casper Hossfield.......New Jersey)
Subject: Re: Want a drum recorder
From: Kplblange@.......
Date: Wed, 20 Nov 2002 10:19:20 EST
Cap, so good to hear from you on the drum record. Sounds as if that is
just what I want. I confess I know little about the drum recorders. I have
only seen them from a distance. Saw one at San Juan Batista near the mission
and almost sitting on the San Andreas Fault! Have seen them working at
Griffith Observatory, too.
Tell me, is there the feature where tick marks are put ever minute or so?
Also, what about ink supply? You mention the pens. As for the assembly, no
problem.
Do you have an idea about shipping costs? I do not see that as a factor
and I almost surely want to buy one of them.
Ken in Gardena, CA
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Help with self leveling Lehman
From: CapAAVSO@.......
Date: Wed, 20 Nov 2002 10:30:52 EST
In a message dated 11/20/02 2:51:37 AM GMT Standard Time, Kplblange@.......
writes:
> I had a Lehman working some years ago and know what a time
> it is to have it stay in neutral. I wonder if I should have make a
> vertical
> one and have plans in an old Scientific American. The problem is that it
> needs springs that best would be make by a machine shop. They are not coil
> springs but flat pieces of metal.
>
> Ken from Gardena, CA
Hi Ken,
A good flat spring is the one Sean-Thomas used in his leaf spring
seismometer. I bought one of these, a plasterer's 14" spackling trowel for
about $20 at Home Depot and removed the handle by drilling out the rivets.
This gave me a 0.025" thick flat spring 4" by 14" which I mounted vertically
and bent over 90 degrees with a lead weight so the free end was horizontal.
An outrigger carried a coil from a 120-Volt relay that dipped between the
poles of a big Alnico magnet to generate a signal voltage. A flat sheet of
copper 4" X 4" farther out on the outrigger sandwiched between eight flat
ceramic magnets provided critical damping and enough additional weight to
give a period of about 1 1/4 seconds. With one of Dave Saum's amp/filters
there was more than enough sensitivity to record microseisims continuously
even on quiet days.
Cap
(Casper Hossfield)
In a message dated 11/20/02 2:51:37 AM GMT Standard Time, Kplblange@....... writes:
I had a Lehman working some years ago and know what a time
it is to have it stay in neutral. I wonder if I should have make a vertical
one and have plans in an old Scientific American. The problem is that it
needs springs that best would be make by a machine shop. They are not coil
springs but flat pieces of metal.
Ken from Gardena, CA
Hi Ken,
A good flat spring is the one Sean-Thomas used in his leaf spring seismometer. I bought one of these, a plasterer's 14" spackling trowel for about $20 at Home Depot and removed the handle by drilling out the rivets. This gave me a 0.025" thick flat spring 4" by 14" which I mounted vertically and bent over 90 degrees with a lead weight so the free end was horizontal. An outrigger carried a coil from a 120-Volt relay that dipped between the poles of a big Alnico magnet to generate a signal voltage. A flat sheet of copper 4" X 4" farther out on the outrigger sandwiched between eight flat ceramic magnets provided critical damping and enough additional weight to give a period of about 1 1/4 seconds. With one of Dave Saum's amp/filters there was more than enough sensitivity to record microseisims continuously even on quiet days.
Cap
(Casper Hossfield)
Subject: Re: Self leveling and about spurious noise
From: Kplblange@.......
Date: Wed, 20 Nov 2002 11:45:19 EST
Tom that suggestion of yours to use water tanks is great. It will not work in
my setup due to a lack of space but it is a good idea.
My seismo has been off for years but may soon be going again. I find so
much on our web and pleased I found it.
When I had it going I was bothered with spurious responses. Many times
the trace was one quarter inch peak to peak. I think it was because I am
seven miles from the Pacific at Manhattan Beach, CA. I have read that waves
cause a shift for miles. Any ideas on that? I have made a rough calculation
of how much the sift was but didn't keep the figures and not sure if all was
valid.
Ken
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Want a drum recorder
From: CapAAVSO@.......
Date: Wed, 20 Nov 2002 11:54:21 EST
In a message dated 11/20/02 3:19:59 PM GMT Standard Time, Kplblange@.......
writes:
>
> Tell me, is there the feature where tick marks are put ever minute or
> so?
> Also, what about ink supply? You mention the pens. As for the assembly, no
>
> problem.
> Do you have an idea about shipping costs? I do not see that as a factor
>
> and I almost surely want to buy one of them.
>
> Ken in Gardena, CA
Hi Ken,
You will have to generate your own tick marks. I did this on a "Geotech" drum
I converted to pen and ink. I used an ordinary quartz kitchen clock. I glued
a little piece of aluminum foil on the second hand and mounted an infra red
diode and a photo transistor side by side on the face of the clock. Once each
minute the second hand reflector jumped under these for exactly one second
and reflected the infrared into the phototransistor to generate a current
that closed a relay mechanically connected to the pen so it lifted the pen
off the paper putting a 1-second gap in the trace every minute. The pen was
the tip assembly of a "Rapidograph" drawing pen that held enough ink to last
24 hours which was how often the paper recording had to be changed. Each
morning I checked the clock error against WWV and marked it on the starting
edge of the recording. The error was pretty consistent at loosing about four
tenths of a second/day. This was back in ~1990 and I was able to time the
first impulse usually to with a few tenths of a second for USGS as station
TXNY in Tuxedo, NY.
I will ship it by "Yellow Freight" because I can take the crate to their main
terminal which is nearby and save some $$s. The weight is marked on the crate
as 192 pounds which I would guess might cost somewhere in the neighborhood of
200-300 dollars from New jersey to California. If you will give me your zip
code I'll get an exact price.
Regards,
Cap
(Casper Hossfield.....New Jersey)
-------------------------------------------------------------------
Original Message:
Cap, so good to hear from you on the drum record. Sounds as if that is
just what I want. I confess I know little about the drum recorders. I have
only seen them from a distance. Saw one at San Juan Batista near the mission
and almost sitting on the San Andreas Fault! Have seen them working at
Griffith Observatory, too.
Tell me, is there the feature where tick marks are put ever minute or so?
Also, what about ink supply? You mention the pens. As for the assembly, no
problem.
Do you have an idea about shipping costs? I do not see that as a factor
and I almost surely want to buy one of them.
Ken in Gardena, CA
__________________________________________________________
In a message dated 11/20/02 3:19:59 PM GMT Standard Time, Kplblange@....... writes:
Tell me, is there the feature where tick marks are put ever minute or so?
Also, what about ink supply? You mention the pens. As for the assembly, no
problem.
Do you have an idea about shipping costs? I do not see that as a factor
and I almost surely want to buy one of them.
Ken in Gardena, CA
Hi Ken,
You will have to generate your own tick marks. I did this on a "Geotech" drum I converted to pen and ink. I used an ordinary quartz kitchen clock. I glued a little piece of aluminum foil on the second hand and mounted an infra red diode and a photo transistor side by side on the face of the clock. Once each minute the second hand reflector jumped under these for exactly one second and reflected the infrared into the phototransistor to generate a current that closed a relay mechanically connected to the pen so it lifted the pen off the paper putting a 1-second gap in the trace every minute. The pen was the tip assembly of a "Rapidograph" drawing pen that held enough ink to last 24 hours which was how often the paper recording had to be changed. Each morning I checked the clock error against WWV and marked it on the starting edge of the recording. The error was pretty consistent at loosing about four tenths of a second/day. This was back in ~1990 and I was able to time the first impulse usually to with a few t
enths of a second for USGS as station TXNY in Tuxedo, NY.
I will ship it by "Yellow Freight" because I can take the crate to their main terminal which is nearby and save some $$s. The weight is marked on the crate as 192 pounds which I would guess might cost somewhere in the neighborhood of 200-300 dollars from New jersey to California. If you will give me your zip code I'll get an exact price.
Regards,
Cap
(Casper Hossfield.....New Jersey)
-------------------------------------------------------------------
Original Message:
Cap, so good to hear from you on the drum record. Sounds as if that is
just what I want. I confess I know little about the drum recorders. I have
only seen them from a distance. Saw one at San Juan Batista near the mission
and almost sitting on the San Andreas Fault! Have seen them working at
Griffith Observatory, too.
Tell me, is there the feature where tick marks are put ever minute or so?
Also, what about ink supply? You mention the pens. As for the assembly, no
problem.
Do you have an idea about shipping costs? I do not see that as a factor
and I almost surely want to buy one of them.
Ken in Gardena, CA
__________________________________________________________
Subject: Re: Want a drum recorder
From: Kplblange@.......
Date: Wed, 20 Nov 2002 12:04:44 EST
Cap, I terribly sorry to say that because of the tremendous weight I decline
to continue with the transaction. I am alone and while I could get someone
to help, do not wish to do so. I am amazed that the unit is that heavy. I
would have problems getting it in place and not sure how that would be
handled.
Thanks for your effort.
Ken
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Want a drum recorder
From: CapAAVSO@.......
Date: Wed, 20 Nov 2002 12:25:11 EST
In a message dated 11/20/02 5:05:50 PM GMT Standard Time, Kplblange@.......
writes:
> Cap, I terribly sorry to say that because of the tremendous weight I decline
>
> to continue with the transaction. I am alone and while I could get someone
>
> to help, do not wish to do so. I am amazed that the unit is that heavy. I
>
> would have problems getting it in place and not sure how that would be
> handled.
> Thanks for your effort.
> Ken
The problem is Sprengnether makes things too good. They are built like a
battleship. I have another one unpacked and just the drum alone is over 100
pounds and to heavy for an old man like me to lift. Geotech also builds stuff
too strong and heavy for me to lift their drum. These things cost thousands
of dollars when they are new and are built to last forever I guess.
Cap
In a message dated 11/20/02 5:05:50 PM GMT Standard Time, Kplblange@....... writes:
Cap, I terribly sorry to say that because of the tremendous weight I decline
to continue with the transaction. I am alone and while I could get someone
to help, do not wish to do so. I am amazed that the unit is that heavy. I
would have problems getting it in place and not sure how that would be
handled.
Thanks for your effort.
Ken
The problem is Sprengnether makes things too good. They are built like a battleship. I have another one unpacked and just the drum alone is over 100 pounds and to heavy for an old man like me to lift. Geotech also builds stuff too strong and heavy for me to lift their drum. These things cost thousands of dollars when they are new and are built to last forever I guess.
Cap
Subject: Re: Help...(Building a pier)
From: meredithlamb meredithlamb@.............
Date: Wed, 20 Nov 2002 12:40:21 -0700
Hi Ian,
For myself and likely for you, alot about making a pier/s
depends on you; how much you can do or want, your space,
your soil/rock underneath, picking a "quiet" location away
from most upstairs traffic/tilt/furnace/washer/dryer, away from
too much water moisture seeping in, running in the signal/power
lines and with consideration of whether you can physically do
it all. Only the individual can estimate/acquire/judge their specific
plus's and minus's of their location for making their own piers
of course.
As for your specific pier dimensions question....it depends on
what you plan to have or have in your possession now. Of
course the pier has to be a greater size (width/length) than any
seismo you have or is planned for. Mine are rectangular, but I
see no problem with round piers....they might be better.
Generally I would say the bigger the better. As for thickness,
I'd give at least 6" if possible....the thicker pier would be less
prone to cracking from environmental influences and weight
put upon it....you've likely be standing/kneeling on it occasionally.
Another important thought to add to the mix of questions....is
whether you want more than one pier per instrument you have
or are planning for. I made 3 piers, but now wish I'd made
more. However, it "maybe" possible to share one pier with
more than one instrument...another consideration as too the
size of the pier. It may also be evident with multiple piers,
that you find that certain piers are more susceptible to tilt
than others you have...I'd put the vertical/s atop the more
susceptible tilting pier and the horizontals atop the more
stable ones in time.
Assuming you survey your available area....the next step
would be to do a test dig in your soil. If the soil is real loose,
how far down does it become more compacted than it was
on top? If its loose no matter how far down you go....you
may have to settle for that depth. If you run into a water
seepage pothole, thats not good. If you run into solid rock,
thats great; as its about the best foundation you can have.
Of course, the height of your seismo/s is another consideration
to plan for, and also the available anticipated height of your
pier from the underside of the house, just for clearance. Their
is alot to consider overall.
Another problem might be whether you want a solid poured
concrete pier or have to improvise with paving blocks and
brick mortar. If space for movement is limited, or its physically
too difficult to mix concrete under your house or move such,
you may have to be forced to choose between the two. One
can only do whats possible in the end for their circumstances.
Adding to the above.....is the likely necessity of enclosing your
piers with a wall/box, and adding any insulation to try to limit
any gross environmental temperature excursions you may have.
Insulation does help alot. I ended up with a rough R42 value,
except for the ground area....its the coolest place I have even
in high temp summer conditions. The vault floor is double
covered with flexible plastic layers, to keep water/moisture
out; and it works well...no rust either that I've noted on the
seismos and misc iron/steel tools/parts therein for some ~7
years of use. I don't use any electric heating or temp control;
all the heavy insulation seems relatively temperature consistant
and/or very slow changing over time....a real help.
So....there is alot to mentally "chew on", or plan or inspect for.
Take care, Meredith
ian@........... wrote:
> a few dimensions would help, width, length and depth of the peer. I hope to be
> making one in the next 6 months. Does the peer have to be the same size as the
> platform it supports all the way down or can it have a small circular cross
> section?
>
> TIA
>
> Ian Smith
>
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Public Seismic Network Mailing List (PSN-L)
Subject: Re: stability of a Lehman
From: john c cole johnccole3@........
Date: Wed, 20 Nov 2002 14:05:33 -0600
Larry, in response to your message sent to Charles about the stability of
the Lehman detector. In support of the stability of the Lehman or
modified lehman detector , here is what i do. I have one detector set up
at approximately 20 stable seconds and it has been running for over two
years .It is housed in a 8'x8' utility building on a concrete slab. It
requires only a minimum of adjustments. I have another modified Lehman
detector set up on a concrete slab in a bigger storage building that is
run at over 30 stable seconds with a minimum and acceptable amount of
adjustments . This detector has both upper and lower ball bearing pivot
points . If the Lehman detector is constructed on a good solid base and
is set up in a fair location then, it will have acceptable stability. As
a rule , i do not post to PSN the data from these detectors but from time
to time i do post from experimental detectors . I know of more than a few
amateur seismologist that are using the Lehman or modified Lehman and are
posting to PSN on a regular basis. JC PS, Larry , you of all people
should know better than to try to set up and run a seismic detector on a
wood floor. Take care .JOHN
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Subject: Re: Want a drum recorder
From: Thomas W Leiper twleiper@........
Date: Wed, 20 Nov 2002 17:47:38 -0500
I'll take the other one for $100... I can pick it up when
I am down in South Jersey tomorrow or Friday.
Tom
On Wed, 20 Nov 2002 09:37:47 EST CapAAVSO@....... writes:
I have two Sprengnether drums brand new in the box, never been unpacked.
You can have one of these for $50...
I'll take the other one for $100... I can pick it up when
I am down in South Jersey tomorrow or Friday.
Tom
On Wed, 20 Nov 2002 09:37:47 EST
CapAAVSO@....... writes:I have two Sprengnether =
drums brand=20
new in the box, never been unpacked. You can have one of these for=20
$50...
Subject: Re: Want a drum recorder
From: CapAAVSO@.......
Date: Wed, 20 Nov 2002 18:49:37 EST
In a message dated 11/20/02 10:49:06 PM GMT Standard Time, twleiper@........
writes:
> I'll take the other one for $100... I can pick it up when
> I am down in South Jersey tomorrow or Friday.
Hi Tom,
Good. Its yours for $50 because I am glad to find a good home for it. It's in
my son's barn so you should make arrangements with him to pick it up. His
name is Bill Hossfield and his address is 935 Warwick Turnpike, Vernon, New
Jersey. Call him at 973 853 9053 and email him at <<
hosfield@................ >> to get directions and make arrangements.
Good luck with it,
Cap
In a message dated 11/20/02 10:49:06 PM GMT Standard Time, twleiper@........ writes:
I'll take the other one for $100... I can pick it up when
I am down in South Jersey tomorrow or Friday
.
Hi Tom,
Good. Its yours for $50 because I am glad to find a good home for it. It's in my son's barn so you should make arrangements with him to pick it up. His name is Bill Hossfield and his address is 935 Warwick Turnpike, Vernon, New Jersey. Call him at 973 853 9053 and email him at << hosfield@................ >> to get directions and make arrangements.
Good luck with it,
Cap
Subject: Stability of a Lehman
From: ChrisAtUpw@.......
Date: Wed, 20 Nov 2002 19:27:11 EST
Hello Charles Patton,
>> There have been numerous discussions about lengthening the period of a
Lehman beyond the approximately 10 sec period and it becomes "unstable."
Let's consider a 'big' 1 metre length boom. The 'natural' period is 2
seconds,
so to get a period of 10 sec, we have to reduce g to g/25. This corresponds
to about 2.3 degrees off the vertical, lowering the mass by 40 mm below the
horizontal. To get 20 sec, we need 0.56 degrees. To get 30 sec we need 0.255
deg.... x60 = 15.3 minutes of arc.... This corresponds to lowering the mass
4.44 mm below the horizontal position, roughly 175 thou.
Now lets consider a small 25 cm boom, with a natural period of 1 sec. To
get a
period of 10 sec, we now have to reduce g to g/100. This corresponds to 0.573
degrees off the vertical, lowering the mass by 2.5 mm below the horizontal.
To get to 20 sec, we need an angle of 0.143 deg. To increase the period to 30
sec, we need an angle of 0.0637 degrees, 3.8 minutes of arc, lowering the
mass by 0.28 mm below the horizontal, roughly 11 thou. This requires
considerable precision. The best that I can easily get with differential
thread supports is ~10 thou per turn.
>> The question is - unstable in what way? The period changes, the centring
fails, sensitivity goes haywire? In particular, if the answer is, "The
centring fails," does the centre just move around, or does the beam "flop" to
one side or the other?
You name it.... With the small suspension angles, a Lehman is very
sensitive to
tilt effects. The support needs to be very rigid. With very small restoring
forces, like g/900, the response becomes sensitive to any frictional and
springy effects in the suspension. The original Lehmans had a knife edge
suspension. Some even had a point suspension. The forces in these suspensions
are high enough to cause deformation of the contact points / edges. This can
give an erratic response such that no two successive swings are similar. This
can be avoided by using either rolling contacts, either a sphere on a flat,
or a cylinder on a crossed cylinder, or by using
flexing wire or foil suspensions.
>> I'm doing some thought experiments during my long commute, and I'm
thinking about the sources of error. In particular it's been mentioned before
that the centre of rotation changes on the flexible hinge designs. That's
intuitive, but how much and in what direction - toward stability or
instability? Has anybody figured out the actual path of the centre of
rotation for a typical Lehman?
In the single foil / wire hinge of the 'Cardan' type, the material must
not be so highly stressed that it can take on a permanent 'set'. The centre
of rotation will be quite close to the frame clamps. You can get erratic
effects with foils 'crinkling' if the two axes are not quite in line or not
parallel. With the crossed foil hinges clamped onto the edges of a plate, the
flex axis moves in an ellipse. Both of these types have a small spring
effect. In the zero force rolling contact type where the foil is essentially
wrapped in a figure of 8 around two cylinders, the flex axis moves in a
circle. The centres of rotation will be at the centres of these curves.
>> Crossed-X flex hinges were mentioned, but in this application with side
force, I don't think they would be any less susceptible to the same
de-centering.
I would expect crossed foil hinges to be ~completely rigid.
>> Another question is the upright's rigidity. Several pounds of weight at
the end of a boom is a fair torque moment which is resisted by the spring
constant of the 'pipe' vertical. How much does this constant vary with
temperature in standard steel?
From memory, Young's modulus varies by about -2x10^-4 / C Deg.
for steel. While this is not a lot, you don't need a lot to change the period
or
upset the balance. Professional seismometers of this type use a braced
upright post. Bracing the upright with either more tube or with L angle would
tend to prevent flexing problems.
The orientation of the horizontal arm needs to be rigid and any
resonances in the system should be suppressed. Some quick calculations
suggest that direct thermal expansion effects on the suspension are not very
large.
Hope that this helps.
Regards,
Chris Chapman
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Public Seismic Network Mailing List (PSN-L)
Subject: A jewelry "slinky" spring earring, with vertical potential?
From: meredithlamb meredithlamb@.............
Date: Wed, 20 Nov 2002 19:57:27 -0700
Hi all,
I noted in a local K-Mart store, in the jewelry section, that there
is a display hangup card with what appears to be a miniture "slinkey"
spring in various sprayed on (bizarre)colors. The spring in its
natural compressed state looks to be ~ 1" outside diameter and ~ 1.5"
long....with other "junk" connection metal attached. It stretches quite
easily and looks to be quite similar to the much larger (and very old)
Slinkey spring toy from "yesteryear". It stretches out some
6-8 inches. I guess it was somehow "adopted" for a large "earring".
My best local hardware store has a big spring variety, but nothing like
this particular shape/size.
In short....it "could" make a small weight mass vertical spring.
Two might allow more added mass weight.
Nope, I wasn't there for myself, my wife was looking at
jewelry.....ha. No, I don't remember the brand, or "theme".
I also didn't have the presense of mind to tell the wife how
beautiful they would be on her.....and later get her items for
myself to tear apart! So....take your wife....errr...Christmas
shopping....to a K-Mart store guys...she can pick the color out.
Get at least three "springs/earrings"...one for each ear and a
"spare"....in case one is somehow lost you know.... One might
as well have something to look forward too when otherwise this
"shopping" is a real drag. Just don't get too enthusiastic if
you bring up the shopping binge thing....women have a way of
getting carried away with jewelry. Of course, as a last resort
you could risk telling the truth; otherwise she might look at
you rather strangely. BTW, this is all very confidential
information from a "secret" source.
Take care, "X"
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: RE: stability of a Lehman
From: "Rolando Benitez" rbenitez@........
Date: Wed, 20 Nov 2002 23:43:14 -0600
Charles,
I have two modified Lehman derivative sensors, both made by John C. Cole,
one is a Mini-Lehman with a stable pendulum period of 14 seconds, it has the
ball bearing/flat surface mountings, the other is a Tmax with a stable
period of 32 seconds, it has the roller bearings supports. I check them once
a week and the last time I have to "center" the Mini, was about 4 months
ago. I am currently tuning/playing with the Tmax but it remains centered if
I do nothing with it. You can check their performance by the results posted
at the PSN web page. I am fortunate enough to have local quakes all the
time, because living in an active area as Central America, there is no
single day without an event. Besides I have 1 of the 10 most active
volcanoes 16 miles away, so my sensors detect high freq events as close as
they can be and as far as the recent 14k Km away, in Asia. The Mini starts
"flopping" at 20 seconds, and the Tmax at around 36 seconds. You can take a
look at pictures and details at John Cole's web page at
http://pages.prodigy.net/fxc/JC.html and at Frank Cooper's at
http://pages.prodigy.net/fxc/.
Hope this helps.
Best regards from Fraijanes, Guatemala.
Rolando
...
...
...
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Public Seismic Network Mailing List (PSN-L)
Subject: Another horizontal boom/mast pivot to consider
From: meredithlamb meredithlamb@.............
Date: Thu, 21 Nov 2002 00:59:39 -0700
Hi all,
With all the discussion on a horizontal boom/mast pivot, it
might be alot simpler to use/make another type mentioned in
the past emails. Its based on the Sprengnether horizontals
general design and has been "revised" for use by John Lahr
on his horizontal; but it essentially is the same type pivot.
See the 5th photo/diagram down from the top of this web page:
http://www.jjlahr.com/science/psn/gldn_psn.html
For other views of the same hinge, See the 2nd & 4th photos
down on this web page:
http://www.geocities.com/meredithlamb/page022.html
The Sprengnether shown beside/with Johns seismo, in the other
same page photos uses the same basic pivot....only laid out
mechanically alittle differently.
I think its one of the best pivot innovations I know of,
and most ingenious of John to come up with the variation.
Theres probably about zero long term problems with this
conpared to other pivot designs. Its frictionless as
John describes in his text.
Take care, Meredith Lamb
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: stability of a Lehman
From: john c cole johnccole3@........
Date: Thu, 21 Nov 2002 11:50:23 -0600
Rolando, when our more educated comrades write to PSN i feel somewhat
inferior because they speak with the utmost authority and speak well . A
simple carpenter like myself would not dare challenge their authority .
I am sure that they have total knowledge of all things pertaining to
seismology. However , when checking all postings world wide i find little
or no evidence in their postings to PSN to confirm this . Some of our
fellow travelers must be using sophisticated professional equipment .
but, is not reflected in their postings . It is common and un disputed
knowledge that the best that any home made long period detector will do
is 8 seconds . A Lehman even when run at that time is somewhat unstable
and is not to be considered a serious instrument. I challenge that
assumption .
For the second time in recent weeks the opportunity has presented
itself to promote the convex to convex theory of suspension . This idea
is the brain child of Mr AL Hrubetz of Dallas ,TX. If your detectors work
well or do not work well the blame or credit should go to him because it
was his original idea .Yes, it is true that i made the gun that did the
ghastly deed but , he was the instigator. I know little of legal matters
but, i believe that makes him and not me responsible . Seriously, the
convex to convex suspension method should become common knowledge for
all the beginning amateur seismologist. When discussing this thing ,
please leave my name out of it . I have nothing to sell or gain . MY one
and only motive is to give the amateur seismologist a decent ,economical
and simple seismic detector to use . Rolando , your response to PSN was
absolutely beautiful and made the point about as good as it could have
been made but,with one exception . . My name should have been omitted . I
want no credit or recognition and i am sure that goes for Al also. You
did a wonderful thing for amateur seismology today Rolando . This was
your finest hour. JC And yes, i feel real good . How sweet it is . PPS,
All responsibility should rest with Frank Cooper,he got me hooked on this
stuff .
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Subject: Re: Another horizontal boom/mast pivot to consider
From: CapAAVSO@.......
Date: Fri, 22 Nov 2002 11:34:51 EST
In a message dated 11/21/02 8:01:16 AM GMT Standard Time,
meredithlamb@............. writes:
> With all the discussion on a horizontal boom/mast pivot, it
> might be alot simpler to use/make another type mentioned in
> the past emails. Its based on the Sprengnether horizontals
> general design and has been "revised" for use by John Lahr
> on his horizontal; but it essentially is the same type pivot.
> .............I think its one of the best pivot innovations I know of,
> and most ingenious of John to come up with the variation.
> Theres probably about zero long term problems with this
> conpared to other pivot designs. Its frictionless as
> John describes in his text.
Hi Meridith
You don't have to be an engineer to realize friction in the lower pivot of a
Lehman will decrease its sensitivity. Lehman I'm sure was aware of that but
he was designing a simple instrument for amateurs that was good enough to get
started. The point-in-a -dimple bottom pivot will always have some stick-slip
friction which will interfere with its sensitivity to small earthquake
movements. if you replace the point with a ball its rolling friction is less
but nevertheless there will still be small residual stick-slip friction. John
Lahr's completely frictionless Sprengnether type wire-under-tension pivot is
much better than ball bearings and just as easy, if not easier to make, and
it stays put rather than slithering around like ball bearings. I use John
Lahr's system with 0.008" music wire, obtainable from any music store, and it
shows the finest detail in the microseisms if I turn up the gain. However,
and this is important, even with frictionless pivots my Lehman is unstable
over time unless I set its period for about 10-15 seconds. I doubt anyone can
do much better with ball bearing pivots unless they are on bed rock and even
then I don't see how they could possibly get month's-long stability at 30-40
second periods as has been claimed in recent postings. My guess is what these
people actually have are strong-motion detectors rather than the Lehmans they
think they have.
Best regards,
Cap
In a message dated 11/21/02 8:01:16 AM GMT Standard Time, meredithlamb@............. writes:
With all the discussion on a horizontal boom/mast pivot, it
might be alot simpler to use/make another type mentioned in
the past emails. Its based on the Sprengnether horizontals
general design and has been "revised" for use by John Lahr
on his horizontal; but it essentially is the same type pivot.
..............I think its one of the best pivot innovations I know of,
and most ingenious of John to come up with the variation.
Theres probably about zero long term problems with this
conpared to other pivot designs. Its frictionless as
John describes in his text.
Hi Meridith
You don't have to be an engineer to realize friction in the lower pivot of a Lehman will decrease its sensitivity. Lehman I'm sure was aware of that but he was designing a simple instrument for amateurs that was good enough to get started. The point-in-a -dimple bottom pivot will always have some stick-slip friction which will interfere with its sensitivity to small earthquake movements. if you replace the point with a ball its rolling friction is less but nevertheless there will still be small residual stick-slip friction. John Lahr's completely frictionless Sprengnether type wire-under-tension pivot is much better than ball bearings and just as easy, if not easier to make, and it stays put rather than slithering around like ball bearings. I use John Lahr's system with 0.008" music wire, obtainable from any music store, and it shows the finest detail in the microseisms if I turn up the gain. However, and this is important, even with frictionless pivots my Lehman is unstable over time unless I set its period
for about 10-15 seconds. I doubt anyone can do much better with ball bearing pivots unless they are on bed rock and even then I don't see how they could possibly get month's-long stability at 30-40 second periods as has been claimed in recent postings. My guess is what these people actually have are strong-motion detectors rather than the Lehmans they think they have.
Best regards,
Cap
Subject: Did quark matter strike Earth? (BBC News)
From: George Bush ke6pxp@.......
Date: Fri, 22 Nov 2002 09:14:13 -0800
Hello-
I just ran across this intersting article on the BBC news. It links two of
my interests together, space and geology:
http://news.bbc.co.uk/1/hi/sci/tech/2502755.stm
I wonder if our PLA network could continue looking for these anamolous events?
George
__________________________________________________________
Public Seismic Network Mailing List (PSN-L)
Subject: Re: Another horizontal boom/mast pivot to consider
From: "Frank Cooper" fxc@.......
Date: Fri, 22 Nov 2002 13:50:43 -0600
OK Cap as a member of the "these people" or the "they" ball bearing =
party, I'll bite,
I'll respond even though I think your purpose is to have a little fun =
and stir the pot a bit. Perhaps we take ourselves too seriously at times =
since "we" all enjoy and are all engaged in a very interesting HOBBY. I =
have to differ with you on a couple of statements in your recent =
postings. You say "John Lahr's completely frictionless Sprengnether =
type wire-under-tension pivot is much better than ball bearings and just =
as easy, if not easier to make, and it stays put rather than slithering =
around like ball bearings."
Have you ever used the ball bearing method? I assume you must speak =
from long experience to back-up your slithering ball bearing =
pronouncement. I have been using a ball bearing at the pivot point of =
my Lehman pendulum for years and it has not "slithered around" once. =
But perhaps I should only "claim." Maybe you also have long experience =
in maintaining a 30 second period with a modified ball bearing Lehman. =
However, that must not be the case since you say "I don't see how they =
could possibly get month's-long stability at 30-40 second periods as has =
been claimed in recent postings." My only suggestion is to try it --- =
you might like it and become "one of these people."=20
And you say "My guess is what these people actually have are =
strong-motion detectors rather than the Lehmans they think they have." =
You speak from the abyss --- you evidently do not check the posting of =
teleseismic events by "these people.". "They" speak louder than your =
words. Perhaps even louder than "they think they have."
Regards to all and a Merry Christmas!
Frank Cooper, Friendswood, Texas, USA
Seismology web site at http://pages.prodigy.net/fxc/
----- Original Message -----=20
From: CapAAVSO@..........
To: psn-l@.................
Sent: Friday, November 22, 2002 10:34 AM
Subject: Re: Another horizontal boom/mast pivot to consider
In a message dated 11/21/02 8:01:16 AM GMT Standard Time, =
meredithlamb@............. writes:
With all the discussion on a horizontal boom/mast pivot, it
might be alot simpler to use/make another type mentioned in
the past emails. Its based on the Sprengnether horizontals
general design and has been "revised" for use by John Lahr
on his horizontal; but it essentially is the same type pivot.
.............I think its one of the best pivot innovations I know =
of,
and most ingenious of John to come up with the variation.
Theres probably about zero long term problems with this
conpared to other pivot designs. Its frictionless as
John describes in his text.
Hi Meridith
You don't have to be an engineer to realize friction in the lower =
pivot of a Lehman will decrease its sensitivity. Lehman I'm sure was =
aware of that but he was designing a simple instrument for amateurs that =
was good enough to get started. The point-in-a -dimple bottom pivot will =
always have some stick-slip friction which will interfere with its =
sensitivity to small earthquake movements. if you replace the point with =
a ball its rolling friction is less but nevertheless there will still be =
small residual stick-slip friction. John Lahr's completely frictionless =
Sprengnether type wire-under-tension pivot is much better than ball =
bearings and just as easy, if not easier to make, and it stays put =
rather than slithering around like ball bearings. I use John Lahr's =
system with 0.008" music wire, obtainable from any music store, and it =
shows the finest detail in the microseisms if I turn up the gain. =
However, and this is important, even with frictionless pivots my Lehman =
is unstable over time unless I set its period for about 10-15 seconds. I =
doubt anyone can do much better with ball bearing pivots unless they are =
on bed rock and even then I don't see how they could possibly get =
month's-long stability at 30-40 second periods as has been claimed in =
recent postings. My guess is what these people actually have are =
strong-motion detectors rather than the Lehmans they think they have.
Best regards,
Cap
OK Cap as a member of the "these people" or the =
"they"=20
ball bearing party, I'll bite,
I'll respond even though I think your purpose =
is to have=20
a little fun and stir the pot a bit. Perhaps we take ourselves too=20
seriously at times since "we" all enjoy and are all engaged in =
a very interesting HOBBY. I have to differ with you on a =
couple of=20
statements in your recent postings. You say "John Lahr's =
completely=20
frictionless Sprengnether type wire-under-tension pivot is much better =
than ball=20
bearings and just as easy, if not easier to make, and it stays put =
rather than=20
slithering around like ball bearings."
Have you ever used the ball bearing method? I =
assume you=20
must speak from long experience to back-up your slithering ball =
bearing=20
pronouncement. I have been using a ball bearing at the pivot point =
of my=20
Lehman pendulum for years and it has not "slithered around" =
once. But=20
perhaps I should only "claim." Maybe you also have long experience in=20
maintaining a 30 second period with a modified ball bearing =
Lehman. =20
However, that must not be the case since you say "I don't see how they =
could=20
possibly get month's-long stability at 30-40 second periods as has been =
claimed=20
in recent postings." My only suggestion is to try it --- you might =
like it=20
and become "one of these people."
And you say "My guess is what these people actually =
have are=20
strong-motion detectors rather than the Lehmans they think they =
have." You=20
speak from the abyss --- you evidently do not check the posting of =
teleseismic=20
events by "these people.". "They" speak louder than your words. =
Perhaps=20
even louder than "they think they have."
Regards to all and a Merry Christmas!
Frank Cooper, Friendswood, Texas, USA
Seismology web site at http://pages.prodigy.net/fxc/<=
BR>
----- Original Message -----
From:=20
CapAAVSO@.......=20
Sent: Friday, November 22, 2002 =
10:34=20
AM
Subject: Re: Another horizontal =
boom/mast=20
pivot to consider
In a message dated 11/21/02 8:01:16 AM GMT =
Standard Time,=20
meredithlamb@.............=
=20
writes:
With all the discussion on a horizontal boom/mast pivot, =
it
might be alot simpler to use/make another type mentioned =
in
the=20
past emails. Its based on the Sprengnether =
horizontals
general=20
design and has been "revised" for use by John Lahr
on his =
horizontal; but=20
it essentially is the same type pivot.
.............I think its =
one of=20
the best pivot innovations I know of,
and most ingenious of John =
to come=20
up with the variation.
Theres probably about zero long term =
problems with=20
this
conpared to other pivot designs. Its frictionless =
as
John=20
describes in his text.
Hi Meridith
You =
don't have=20
to be an engineer to realize friction in the lower pivot of a Lehman =
will=20
decrease its sensitivity. Lehman I'm sure was aware of that but he was =
designing a simple instrument for amateurs that was good enough to get =
started. The point-in-a -dimple bottom pivot will always have some =
stick-slip=20
friction which will interfere with its sensitivity to small earthquake =
movements. if you replace the point with a ball its rolling friction =
is less=20
but nevertheless there will still be small residual stick-slip =
friction. John=20
Lahr's completely frictionless Sprengnether type wire-under-tension =
pivot is=20
much better than ball bearings and just as easy, if not easier to =
make, and it=20
stays put rather than slithering around like ball bearings. I use John =
Lahr's=20
system with 0.008" music wire, obtainable from any music store, and it =
shows=20
the finest detail in the microseisms if I turn up the gain. However, =
and this=20
is important, even with frictionless pivots my Lehman is unstable over =
time=20
unless I set its period for about 10-15 seconds. I doubt anyone can do =
much=20
better with ball bearing pivots unless they are on bed rock and even =
then I=20
don't see how they could possibly get month's-long stability at 30-40 =
second=20
periods as has been claimed in recent postings. My guess is what these =
people=20
actually have are strong-motion detectors rather than the Lehmans they =
think=20
they have.
Best=20
regards,
Cap
Subject: Re: Another horizontal boom/mast pivot to consider
From: CapAAVSO@.......
Date: Fri, 22 Nov 2002 16:54:30 EST
In a message dated 11/22/02 7:49:11 PM GMT Standard Time, fxc@....... writes:
> OK Cap as a member of the "these people" or the "they" ball bearing party,
> I'll bite,
> I'll respond even though I think your purpose is to have a little fun and
> stir the pot a bit.
Well, yes, Frank. As a matter of fact I did mean to maybe "have some fun" as
you say, stirring the pot a bit and hopefully get some discussion going
concerning some the wild claims you guys have made that are not in keeping
with what others have said over the years on the PSN. First of all I'm sure
most will agree John Cole's ball bearings have less friction than a simple
point-in-a-dimple pivot. But good as they are, they are not as good as John
Lahr's modified Sprengnether pivot that has no friction at all and can't
slither and is simpler and easy to make. And what does pivot friction have to
do with long term stability anyway? Recent postings have been about the pier
and the soil it's on and how soil moisture and temperature and nearby traffic
affect stability of the period. Nobody even mentioned the pivots until you
guys came along claiming to solve all these problems with ball bearings.
Where is your evidence other than testimonials? What are the mechanical
principles and engineering evidence that pivot friction is the reason Lehmans
are unstable? You say: "My only suggestion is to try it --- you might like it
and become "one of these people". Well, I would, Frank, if I thought it would
work but I already have a frictionless pivot that is better than John Cole's
and no way can I set my Lehman's period at >20 seconds and have it stay
there. I am not conviced the ball bearings will do what you say they will. I
am not one to buy snake oil :-)
Best regards,
Cap
In a message dated 11/22/02 7:49:11 PM GMT Standard Time, fxc@....... writes:
OK Cap as a member of the "these people" or the "they" ball bearing party, I'll bite,
I'll respond even though I think your purpose is to have a little fun and stir the pot a bit.
Well, yes, Frank. As a matter of fact I did mean to maybe "have some fun" as you say, stirring the pot a bit and hopefully get some discussion going concerning some the wild claims you guys have made that are not in keeping with what others have said over the years on the PSN. First of all I'm sure most will agree John Cole's ball bearings have less friction than a simple point-in-a-dimple pivot. But good as they are, they are not as good as John Lahr's modified Sprengnether pivot that has no friction at all and can't slither and is simpler and easy to make. And what does pivot friction have to do with long term stability anyway? Recent postings have been about the pier and the soil it's on and how soil moisture and temperature and nearby traffic affect stability of the period. Nobody even mentioned the pivots until you guys came along claiming to solve all these problems with ball bearings. Where is your evidence other than testimonials? What are the mechanical principles and engineering evidence that pivot
friction is the reason Lehmans are unstable? You say: "My only suggestion is to try it --- you might like it and become "one of these people". Well, I would, Frank, if I thought it would work but I already have a frictionless pivot that is better than John Cole's and no way can I set my Lehman's period at >20 seconds and have it stay there. I am not conviced the ball bearings will do what you say they will. I am not one to buy snake oil :-)
Best regards,
Cap
Subject: Re: Another horizontal boom/mast pivot to consider
From: "Frank Cooper" fxc@.......
Date: Fri, 22 Nov 2002 18:52:23 -0600
Hello Cap,
You write, "the wild claims you guys have made that are not in keeping =
with what others have said over the years on the PSN." I am not aware =
of codified PSN doctrine. Should we heretics kneel in humble submission =
and admit our sins and ask for forgiveness? I vote for the scientific =
method.=20
And you write, "You say, My only suggestion is to try it --- you might =
like it and become "one of these people". Well, I would, Frank, if I =
thought it would work but I already have a frictionless pivot that is =
better than John Cole's and no way can I set my Lehman's period at >20 =
seconds and have it stay there. I am not convinced the ball bearings =
will do what you say they will. I am not one to buy snake oil :-)" I =
thought your attitude died with the middle ages. Most of us accept =
evidence over "I am convinced."
And you write, "But good as they are, they are not as good as John =
Lahr's modified Sprengnether pivot that has no friction at all and can't =
slither and is simpler and easy to make. " I do not have any experience =
with John Lahr's modified Sprengnether pivot and therefore withhold =
judgment. I have a lot of respect for John Lahr and I think he would =
have been the first to withhold judgment about the ball bearing method =
until he had all the facts which you lack.
Regards,
Frank
----- Original Message -----=20
From: CapAAVSO@..........
To: psn-l@.................
Sent: Friday, November 22, 2002 3:54 PM
Subject: Re: Another horizontal boom/mast pivot to consider
In a message dated 11/22/02 7:49:11 PM GMT Standard Time, fxc@....... =
writes:
OK Cap as a member of the "these people" or the "they" ball bearing =
party, I'll bite,
I'll respond even though I think your purpose is to have a little =
fun and stir the pot a bit.
Well, yes, Frank. As a matter of fact I did mean to maybe "have some =
fun" as you say, stirring the pot a bit and hopefully get some =
discussion going concerning some the wild claims you guys have made that =
are not in keeping with what others have said over the years on the PSN. =
First of all I'm sure most will agree John Cole's ball bearings have =
less friction than a simple point-in-a-dimple pivot. But good as they =
are, they are not as good as John Lahr's modified Sprengnether pivot =
that has no friction at all and can't slither and is simpler and easy to =
make. And what does pivot friction have to do with long term stability =
anyway? Recent postings have been about the pier and the soil it's on =
and how soil moisture and temperature and nearby traffic affect =
stability of the period. Nobody even mentioned the pivots until you guys =
came along claiming to solve all these problems with ball bearings. It =
amazes me that you critize a method with which you have no experience? =
What are the mechanical principles and engineering evidence that pivot =
friction is the reason Lehmans are unstable? You say: "My only =
suggestion is to try it --- you might like it and become "one of these =
people". Well, I would, Frank, if I thought it would work but I already =
have a frictionless pivot that is better than John Cole's and no way can =
I set my Lehman's period at >20 seconds and have it stay there. I am not =
conviced the ball bearings will do what you say they will. I am not one =
to buy snake oil :-)
Best regards,
Cap
Hello Cap,
You write, "the wild claims you guys have made =
that are=20
not in keeping with what others have said over the years on the =
PSN." I am=20
not aware of codified PSN doctrine. Should we heretics =
kneel in=20
humble submission and admit our sins and ask for =
forgiveness? I=20
vote for the scientific method.
And you write, "You say, My only suggestion is =
to try it=20
--- you might like it and become "one of these people". Well, I would, =
Frank, if=20
I thought it would work but I already have a frictionless pivot that is =
better=20
than John Cole's and no way can I set my Lehman's period at >20 =
seconds and=20
have it stay there. I am not convinced the ball bearings will do what =
you say=20
they will. I am not one to buy snake oil :-)" I thought your =
attitude died with the middle ages. Most of us accept evidence =
over "I am=20
convinced."
And you write, =
"But good as=20
they are, they are not as good as John Lahr's modified Sprengnether =
pivot that=20
has no friction at all and can't slither and is simpler and easy to =
make.=20
" I do not have any experience with John Lahr's modified =
Sprengnether=20
pivot and therefore withhold judgment. I have a lot of respect for =
John=20
Lahr and I think he would have been the first to withhold judgment about =
the=20
ball bearing method until he had all the facts which =
you lack.
Regards,
Frank
----- Original Message -----
From:=20
CapAAVSO@.......=20
Sent: Friday, November 22, 2002 =
3:54=20
PM
Subject: Re: Another horizontal =
boom/mast=20
pivot to consider
In a message dated 11/22/02 7:49:11 PM GMT =
Standard Time,=20
fxc@....... writes:
OK Cap as a member of the "these people" or the "they" =
ball=20
bearing party, I'll bite,
I'll respond even though I think your purpose =
is to have=20
a little fun and stir the pot a bit.
Well,=20
yes, Frank. As a matter of fact I did mean to maybe "have some fun" as =
you=20
say, stirring the pot a bit and hopefully get some discussion going =
concerning=20
some the wild claims you guys have made that are not in keeping with =
what=20
others have said over the years on the PSN. First of all I'm sure most =
will=20
agree John Cole's ball bearings have less friction than a simple=20
point-in-a-dimple pivot. But good as they are, they are not as good as =
John=20
Lahr's modified Sprengnether pivot that has no friction at all and =
can't=20
slither and is simpler and easy to make. And what does pivot friction =
have to=20
do with long term stability anyway? Recent postings have been about =
the pier=20
and the soil it's on and how soil moisture and temperature and nearby =
traffic=20
affect stability of the period. Nobody even mentioned the pivots until =
you=20
guys came along claiming to solve all these problems with ball =
bearings. It=20
amazes me that you critize a method with which you have no experience? =
What=20
are the mechanical principles and engineering evidence that pivot =
friction is=20
the reason Lehmans are unstable? You say: "My only suggestion is to =
try it ---=20
you might like it and become "one of these people". Well, I would, =
Frank, if I=20
thought it would work but I already have a frictionless pivot that is =
better=20
than John Cole's and no way can I set my Lehman's period at >20 =
seconds and=20
have it stay there. I am not conviced the ball bearings will do what =
you say=20
they will. I am not one to buy snake oil :-)
Best=20
regards,
Cap
Subject: Re: Another horizontal boom/mast pivot to consider
From: ChrisAtUpw@.......
Date: Fri, 22 Nov 2002 20:17:21 EST
In a message dated 22/11/2002, CapAAVSO@....... writes:
> The point-in-a -dimple bottom pivot will always have some stick-slip
> friction which will interfere with its sensitivity to small earthquake
> movements. If you replace the point with a ball its rolling friction is
> less but nevertheless there will still be small residual stick-slip
> friction.
Hi there Cap,
Sorry, but there should be no residual stick slip friction in a rolling
contact on a perfectly flat surface. Obviously, if you try to roll a ball on
a rough surface there would be variable resistance, but a surface can be
polished to optical precision and any resistance reduced below observable
limits. The axis of rotation with a sphere on a flat is very precisely
defined.
John Lahr's completely frictionless Sprengnether type wire-under-tension
pivot is
> much better than ball bearings and just as easy, if not easier to make, and
> it stays put rather than slithering around like ball bearings. I use John
> Lahr's system with 0.008" music wire, obtainable from any music store, and
> it shows the finest detail in the microseisms if I turn up the gain.
Flexing wires and foils have very low friction, but it is not
identically zero due to changing stresses, metal flow and relaxation over
time. Single flexing wires and foils do not have an entirely stable hinge
point with time and temperature. The crossed foils and wires are better in
this respect. You want the rotation axis to be extremely stable.
However, and this is important, even with frictionless pivots my Lehman is
unstable
> over time unless I set its period for about 10-15 seconds. I doubt anyone
> can do much better with ball bearing pivots unless they are on bed rock and
> even then I don't see how they could possibly get month's-long stability at
> 30-40 second periods as has been claimed in recent postings. My guess is
> what these people actually have are strong-motion detectors rather than the
> Lehmans they think they have.
OK, your system is not completely stable over time. Can you tell us why
this is? If nothing changes, it should be perfectly stable! Do temperature
changes, or large rates of change of temperature, effect it? Does it react to
rain? Wind? Frost? Time of day? Do the offsets build up gradually, are they
sudden or random? Do the mounting screws rest on flat plates glued to the
base plinth?
There are many factors which can effect the stability. Look at the Tmax
design. What do you notice? I noticed that the base was made out of steel
which is more rigid than Aluminum and more importantly, that it was much
wider than 'traditional' Lehman designs. Ideally, you should use an
equilateral triangle, like Sprengnether. The support screws will be steel in
steel, not steel or brass in Al, so differential expansion movements should
be less of a problem.
If someone is getting better results than me, I ask myself what I am
doing or not doing differently and what are the limitiations of my equipment
and my site.
Regards,
Chris Chapman
In a message dated 22/11/2002, CapAAVSO@....... writes:
The point-in-a -dimple bottom pivot will always have some stick-slip friction which will interfere with its sensitivity to small earthquake movements. If you replace the point with a ball its rolling friction is less but nevertheless there will still be small residual stick-slip friction.
Hi there Cap,
Sorry, but there should be no residual stick slip friction in a rolling contact on a perfectly flat surface. Obviously, if you try to roll a ball on a rough surface there would be variable resistance, but a surface can be polished to optical precision and any resistance reduced below observable limits. The axis of rotation with a sphere on a flat is very precisely defined.
John Lahr's completely frictionless Sprengnether type wire-under-tension pivot is
much better than ball bearings and just as easy, if not easier to make, and it stays put rather than slithering around like ball bearings. I use John Lahr's system with 0.008" music wire, obtainable from any music store, and it shows the finest detail in the microseisms if I turn up the gain.
Flexing wires and foils have very low friction, but it is not identically zero due to changing stresses, metal flow and relaxation over time. Single flexing wires and foils do not have an entirely stable hinge point with time and temperature. The crossed foils and wires are better in this respect. You want the rotation axis to be extremely stable.
However, and this is important, even with frictionless pivots my Lehman is unstable
over time unless I set its period for about 10-15 seconds. I doubt anyone can do much better with ball bearing pivots unless they are on bed rock and even then I don't see how they could possibly get month's-long stability at 30-40 second periods as has been claimed in recent postings. My guess is what these people actually have are strong-motion detectors rather than the Lehmans they think they have.
OK, your system is not completely stable over time. Can you tell us why this is? If nothing changes, it should be perfectly stable! Do temperature changes, or large rates of change of temperature, effect it? Does it react to rain? Wind? Frost? Time of day? Do the offsets build up gradually, are they sudden or random? Do the mounting screws rest on flat plates glued to the base plinth?
There are many factors which can effect the stability. Look at the Tmax design. What do you notice? I noticed that the base was made out of steel which is more rigid than Aluminum and more importantly, that it was much wider than 'traditional' Lehman designs. Ideally, you should use an equilateral triangle, like Sprengnether. The support screws will be steel in steel, not steel or brass in Al, so differential expansion movements should be less of a problem.
If someone is getting better results than me, I ask myself what I am doing or not doing differently and what are the limitiations of my equipment and my site.
Regards,
Chris Chapman
Subject: Lightweight sensors
From: Bobhelenmcclure@.......
Date: Sat, 23 Nov 2002 00:40:26 EST
Hi all,
Many years ago, after reading an Amateur Scientist article (July 1957) on
swinging gate seismometers, I built a sensor based in part on the information
in the article. Its design, of course, was greatly affected by what raw
material I had around, and what could be obtained from friends and the local
hardware store. You can read a description of it at John Lahr's web page,
http://www.jjlahr.com/science/psn/mcclure/index.html
Originally, it was fitted out with photo-optical sensing of pendulum
position. The image of a pilot lamp filament was projected through a short
focal length lens on the pendulum to a pair of photocells, hooked up parallel
in voltage opposition. The differential voltage output was fed to a
homebuilt potentiometric recorder. It was plagued with drift problems. It
never took long for the filament image to end up totally on one of the
photocells. I gave up my efforts and went on to other interests.
In the past two years, my interest was revived by a former colleague, who
wanted me to participate in a tripartite local network he was wanting to set
up. He loaned me an old vertical short period Strengnether to operate. This
got me going very heavily into programming and signal processing, using
Visual Basic. We also had to solve the problem of time synchronization of
recordings made at separated sites, and how to set up the sensors to have the
same period and damping, so that response differences would not distort our
time-of-arrival estimates.
After all this, I was inspired to take my old sensor and fit it out with a
pickup coil and magnet to convert it to velocity sensing. The pendulum is
short, about 12 inches to the radius of gyration, with a total mass of 66
grams. I had no intention of trying for a natural period of more than 12
seconds, because in my tripartite work, I designed a digital filter that
could extend the useful range of the sensor to as much as 50 seconds, and
which furthermore matched the amplitude and phase response of such a long
period sensor. It is presently set for a natural period of 11 seconds, and
holds its centering without any attention. I really don't know what natural
period could be achieved. Certainly more than 11 seconds. The data obtained
from it after broadband digital filtering to emulate a 32 second period
sensor, matches well what I see from the nearby LDEO PAL site, 19 miles from
me, except for my higher local noise level.
My seismo colleague and I are now motivated to build some more sensors of
lightweight design. Pivots are critical. The old sensor uses steel needles
and sapphire bearing cups. I do not know where I could obtain more sapphire
bearings, so I am considering the use of mini ball pivots. From experiments
with diagmagnetic supported upright pendulums, I have discovered (following a
suggestion from Chris Chapman) that the ball point nib from a BIC pen makes a
very good pivot. The ball is highly polished, about 1 mm diameter. You just
insert the whole little brass nib into a hole in the boom, epoxy it in place,
and you have your pivot. It should rest against a hard flat polished
surface. Glass works, but a sapphire plate would be better. I favor a rigid
strut (no wire) for mounting the upper pivot. If the upper pivot plate
normal points to the center of gravity of the pendulum, there will be no
lateral forces at balance on the pivots.
I encourage others build lightweight sensors, large or small, something
like John Cole's T Max, for example. After all, we are no longer driving
galvanometers, just high impedance input dc amplifiers. The only
justification for weight that I can see is greater resistance to air
currents. You will also find, if you use my magnet and coil design, that you
will not need any damping other than that obtained by a shunt resistance
across the coil. The resistance required will be much higher than the coil
resistance, so that there will be no loss of signal.
I am willing to provide more information on how to wind the 800-turn coil,
and how to filter your data to achieve long period results. I can write
post-filter programs for you for enhancing any data file, but I have to know
the file format.
Cheers,
Bob McClure
Hi all,
Many years ago, after reading an Amateur Scientist article (July 1957) on swinging gate seismometers, I built a sensor based in part on the information in the article. Its design, of course, was greatly affected by what raw material I had around, and what could be obtained from friends and the local hardware store. You can read a description of it at John Lahr's web page,
http://www.jjlahr.com/science/psn/mcclure/index.html
Originally, it was fitted out with photo-optical sensing of pendulum position. The image of a pilot lamp filament was projected through a short focal length lens on the pendulum to a pair of photocells, hooked up parallel in voltage opposition. The differential voltage output was fed to a homebuilt potentiometric recorder. It was plagued with drift problems. It never took long for the filament image to end up totally on one of the photocells. I gave up my efforts and went on to other interests.
In the past two years, my interest was revived by a former colleague, who wanted me to participate in a tripartite local network he was wanting to set up. He loaned me an old vertical short period Strengnether to operate. This got me going very heavily into programming and signal processing, using Visual Basic. We also had to solve the problem of time synchronization of recordings made at separated sites, and how to set up the sensors to have the same period and damping, so that response differences would not distort our time-of-arrival estimates.
After all this, I was inspired to take my old sensor and fit it out with a pickup coil and magnet to convert it to veloc