PSN-L Email List Message
Subject: Re: Vertical Sensor
From: "tchannel" tchannel@..............
Date: Sun, 10 Dec 2006 18:51:39 -0700
Chris, Thanks, these are great sites, and just what I needed. Ted
----- Original Message -----=20
From: ChrisAtUpw@..........
To: psn-l@.................
Sent: Sunday, December 10, 2006 6:03 PM
Subject: Re: Vertical Sensor
In a message dated 2006/12/10, tchannel@.............. writes:
I am thinking I would like to build a vertical sensor. I have read =
that the AS1 has a period of 1.5 seconds, but is extended =
electronically.
Q 1 Is there a program which does this? Maybe an article which =
explains it.
Hi Ted,
In thinking that, remember that vertical seismometers are more =
difficult to build and to set up than horizontal ones. Having access to =
a small metal turning lathe and a drilling / milling machine are very =
helpful. Quite a lot of 'practical machanics' are involved and also =
various sources of constructional materials.=20
Some drawings for the AS-1 are on John Lahr's website. See =
http://jclahr.com/science/psn/as1/index.html=20
An electromagnetic damper to replace the messy oil damper is =
described at =
http://jclahr.com/science/psn/chapman/as1%20damping/index.html
=20
The period can be extended with the Robert' circuit or an =
adaption of it. See http://jclahr.com/science/psn/roberts/index.html=20
You can get stable periods out to about 4.5 secs with steel =
springs, but any further extension needs springs wound with / made of =
Ni-SpanC alloy to control the stiffness / temperature variations. A =
'fairly happy' compromise might be to set up the seismometer with a =
steel spring for ~3 secs period and to then extend this to 30 secs, =
electronically or in software. If you do it in software, you really need =
a 16 bit ADC, since your dynamic range is reduced by maybe x100. Plan to =
cover the periods around 20 secs fairly typical of Rayleigh waves.
Q 2 I have articles on the AS1 which shows its basic design. Is =
there an article showing "how to" build your own Vertical?
My basic questions would be over all dimensions, and locating the =
proper spring.
There is a drawing of a similar device built by Dewayne Hill =
See http://jclahr.com/science/psn/hill/index.html
and a prototype of a rather better construction at =
http://quake.eas.gatech.edu/Instruments/LPVERT0.htm
It might be possible to build one like this inside a glass vessel =
or a tubular enclosure. Allan Coleman used an Al damper casing from a =
scrap yard. A serious problem with vertical sensors is that they are =
sensitive to air density changes / wind noise. These noise levels can be =
100 times that of a horizontal seismometer.
Also have a look at the EAS vertical and the drawings in the EAS =
Manual at http://www.eaiinfo.com/EAI2004/Index.htm This uses the ready =
made 60 deg agate bearings produced for chemical balances. However, =
there is no reason why you should not use a crossed rod Carbide =
suspension, or the dual foil one of the LPVERTO. The LP construction =
would enable you to add an air flotation chamber on the opposite side of =
the arm to the mass to greatly reduce atmospheric noise. Something like =
a miniature Al drinks can, drilled, emptied, rinsed out and then =
resealed? =20
Have a look at the STM-8 designed by Sean Morrissey at =
http://www.eas.slu.edu/People/STMorrissey/index.html and read his notes =
at http://psn.quake.net/info/stm-mail.zip
Keith has a working seisometer of this type with photos at =
http://www.bryantlabs.net/seismo.html =20
Q 3 On a different subject. I am in Idaho and sure would like to =
find someone in Idaho to share .PSN files and notes with. When I record =
an event I would love to compare my signal with other local stations. =
Please if you are in the area or know of a station, near Boise, let me =
know.
Look up all registered American stations? See links on the =
World Map at http://www.sydneystormcity.com/map.htm There is Don Sieber =
in Boise and Jan Marshall in Nampa, both close to you. There is also an =
associated contact and equipment list. There are also several =
educational groups operating across the USA.
Since P waves travel at maybe 8 km / sec you might also =
consider anyone 100 to 300 km distant?
Can you set up a website with photos of your seismometer / =
alternatively send photos to John Lahr to display?
Regards,
Chris, Thanks, these are great =
sites, and=20
just what I needed. Ted
----- Original Message -----
Sent: Sunday, December 10, 2006 =
6:03=20
PM
Subject: Re: Vertical =
Sensor
In a=20
message dated 2006/12/10, tchannel@..............=20
writes:
I am thinking I would like to build a vertical =
sensor. I=20
have read that the AS1 has a period of 1.5 seconds, but is extended=20
electronically.
Q 1 Is there a program which does this? =
Maybe=20
an article which explains it.
Hi=20
Ted,
In thinking that, =
remember=20
that vertical seismometers are more difficult to build and to set up =
than=20
horizontal ones. Having access to a small metal turning lathe and a =
drilling /=20
milling machine are very helpful. Quite a lot of 'practical machanics' =
are=20
involved and also various sources of constructional materials.=20
Some drawings for the =
AS-1 are on=20
John Lahr's website. See http://jclahr.com/science/psn/as1/index.html=20
An electromagnetic damper =
to=20
replace the messy oil damper is described at=20
=
http://jclahr.com/science/psn/chapman/as1%20damping/index.html
&=
nbsp; =20
The period can be extended =
with the=20
Robert' circuit or an adaption of it. See=20
http://jclahr.com/science/psn/roberts/index.html=20
You can get stable =
periods out to=20
about 4.5 secs with steel springs, but any further extension needs =
springs=20
wound with / made of Ni-SpanC alloy to control the stiffness / =
temperature=20
variations. A 'fairly happy' compromise might be to set up the =
seismometer=20
with a steel spring for ~3 secs period and to then extend this to 30 =
secs,=20
electronically or in software. If you do it in software, you really =
need a 16=20
bit ADC, since your dynamic range is reduced by maybe x100. Plan to =
cover the=20
periods around 20 secs fairly typical of Rayleigh waves.
Q 2 I have articles on the AS1 which shows its =
basic=20
design. Is there an article showing "how to" build your own =
Vertical?
My=20
basic questions would be over all dimensions, and locating the =
proper=20
spring.
There =
is a=20
drawing of a similar device built by Dewayne Hill See=20
http://jclahr.com/science/psn/hill/index.html
and a prototype =
of a=20
rather better construction at=20
=
http://quake.eas.gatech.edu/Instruments/LPVERT0.htm
&n=
bsp;=20
It might be possible to build one like this inside a glass vessel or a =
tubular=20
enclosure. Allan Coleman used an Al damper casing from a scrap yard. A =
serious=20
problem with vertical sensors is that they are sensitive to air =
density=20
changes / wind noise. These noise levels can be 100 times that of a =
horizontal=20
seismometer.
Also have a look at the EAS =
vertical=20
and the drawings in the EAS Manual at =
http://www.eaiinfo.com/EAI2004/Index.htm=20
This uses the ready made 60 deg agate bearings produced for chemical =
balances.=20
However, there is no reason why you should not use a crossed rod =
Carbide=20
suspension, or the dual foil one of the LPVERTO. The LP construction =
would=20
enable you to add an air flotation chamber on the opposite side of the =
arm to=20
the mass to greatly reduce atmospheric noise. Something like a =
miniature Al=20
drinks can, drilled, emptied, rinsed out and then resealed? =20
Have a look at the STM-8 designed by Sean =
Morrissey=20
at http://www.eas.slu.edu/People/STMorrissey/index.html and read his =
notes at=20
http://psn.quake.net/info/stm-mail.zip
Keith has a working =
seisometer of=20
this type with photos at http://www.bryantlabs.net/seismo.html =
Q 3 On a different subject. I am in Idaho =
and sure=20
would like to find someone in Idaho to share .PSN files and notes =
with. When=20
I record an event I would love to compare my signal with other local =
stations. Please if you are in the area or know of a station, =
near=20
Boise, let me =
know.
=20
Look up all registered American stations? See links on the World Map =
at=20
http://www.sydneystormcity.com/map.htm There is Don Sieber in Boise =
and Jan=20
Marshall in Nampa, both close to you. There is also an associated =
contact and=20
equipment list. There are also several educational groups operating =
across the=20
USA.
Since P waves travel =
at maybe=20
8 km / sec you might also consider anyone 100 to 300 km=20
distant?
Can you set up a =
website=20
with photos of your seismometer / alternatively send photos to John =
Lahr to=20
display?
=20
Regards,
Chris =
Chapman=20
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