In a message dated 28/08/05, paleoartifact@......... writes:

> Subj:Re: Simple broadband Seismometer
> From:    paleoartifact@......... (meredith lamb)
> 
> Congratulations Dave!  Amazing perseverance and effort went into this!
> 
> On the surface; it sounds like this specific MET, it could well make all the 
> various designs of older horizontal mechanisms and sensors rather obsolete.  
> 
> It seems that the LTC1043 is more available in european/asia areas.  Would 
> be interested in any possible U.S.A., distributors (and rough price)

       See www.digikey.com LTC1043CN-ND  18 pin DIP at US $5.13

    Jeff Witt has a good bridge circuit using the LTC1043. See www.linear.com 
Application Note AN87 p87

       While you can get Platinum wire and foil and also gold for making 
electrodes, they are expensive. Have you tried making the electrodes out of 
graphite? You can get single crystal graphite sheet. The central electrode rods from 
dry batteries are another convenient source. Battery electrodes usually come 
with a crimped brass cap. You can get silver and copper metallic paints to 
make a bond with graphite sheet. You can also use conical electrodes.

    Needle valves can give very non linear flow characteristics with 
differing flow rates. A more linear variable restriction may be obtained by squeezing 
flexible tubing (silicone rubber?) in between two flat strips of metal or 
plywood. 
       I have used this to provide very tiny leak rates by putting a wire 
down the centre of the tube before it is clamped. You could also use thin nylon 
rod or monofilament to give a non conducting core. The fluid sees two tiny 
triangular tubes between the sides of the wire and the two tube surfaces.
 
    Nicolas d'Oreye 
http://edoc.bib.ucl.ac.be:81/ETD-db/collection/available/BelnUcetd-10172003-155611/ describes the flow and period calculations fairly 
fully in his thesis, although he applies it to a precision water tiltmeter. It 
is in French, so you may need http://babelfish.altavista.com/   

       On the subject of reducing the effects of surface tension, it should 
be possible to fit a very thin rubber membrane over the ends of the tube when 
using a capacitative detector --> no free surface. This would certainly be 
worth trying.

       I prefer capacitative sensing for measuring the height of water 
columns. The dielectric constant of water is about 80. Oil is usually about 2. This 
enables you to use high purity water which greatly reduces corrosion problems. 
You can use marine varnish to protect metal surfaces. 

> On 8/28/05, Dave Nelson <davefnelson@.......> wrote:
> >> I have been intrigued by the concept of using a liquid as the seismic 
>> mass in a broadband instrument for some time. The original thought came the 
>> idea that a damping plate was being moved through a liquid -- why not move the 
>> liquid through the damping plate. I have also studied the MET seismometer (I 
>> operate a CME MET vertical seismometer in my home system) and have a 
>> moderate understanding of its principals and the electrochemistry involved.


> I prefer the telephone for detail discussion as I am not a good typist. I 
> am from the old school where a secretary did the typing so I am bit slow on 
> 

       I will let you into two secrets! You can get programs to teach you to 
type! It took me about a week to get reasonably proficient.
       You can also get programs which take a microphone input and give you a 
printed word output.... 

       Regards,

       Chris Chapman
In a message=20=
dated 28/08/05, paleoartifact@......... writes:



Subj:Re: Simple broadban=
d Seismometer

From:    paleoartifact@......... (meredith lamb)



Congratulations Dave!  Amazing perseverance and effort went into th=
is!



On the surface; it sounds like this specific MET, it could well make all=
 the various designs of older horizontal mechanisms and sensors rather obsol=
ete.  



It seems that the LTC1043 is more available in european/asia areas. &nbs=
p;Would be interested in any possible U.S.A., distributors (and rough price)=




       See www.digikey.com LTC1043CN-ND  18 pin DIP at US $5.13



    Jeff Witt has a good bridge circuit using the LTC1043=
.. See www.linear.com Application Note=
 AN87 p87



       While you can get Platinum wire and=
 foil and also gold for making electrodes, they are expensive. Have you trie=
d making the electrodes out of graphite? You can get single crystal graphite=
 sheet. The central electrode rods from dry batteries are another convenient=
 source. Battery electrodes usually come with a crimped brass cap. You can g=
et silver and copper metallic paints to make a bond with graphite sheet. You=
 can also use conical electrodes.



    Needle valves can give very non linear flow character=
istics with differing flow rates. A more linear variable restriction may be=20=
obtained by squeezing flexible tubing (silicone rubber?) in between two flat=
 strips of metal or plywood.=20

       I have used this to provide very ti=
ny leak rates by putting a wire down the centre of the tube before it is cla=
mped. You could also use thin nylon rod or monofilament to give a non conduc=
ting core. The fluid sees two tiny triangular tubes between the sides of the=
 wire and the two tube surfaces.

=20

    Nicolas d'Oreye http://edoc.bib.u=
cl.ac.be:81/ETD-db/collection/available/BelnUcetd-10172003-155611/ descr=
ibes the flow and period calculations fairly fully in his thesis, although h=
e applies it to a precision water tiltmeter. It is in French, so you may nee=
d http://babelfish.altavista.com/   



       On the subject of reducing the effe=
cts of surface tension, it should be possible to fit a very thin rubber memb=
rane over the ends of the tube when using a capacitative detector --> no=20=
free surface. This would certainly be worth trying.



       I prefer capacitative sensing for m=
easuring the height of water columns. The dielectric constant of water is ab=
out 80. Oil is usually about 2. This enables you to use high purity water wh=
ich greatly reduces corrosion problems. You can use marine varnish to protec=
t metal surfaces.=20



On 8/28/05, Dave Nelson<=
/B> <davefnelson@.......> w=
rote:

I have been intrigued by th=
e concept of using a liquid as the seismic mass in a broadband instrument fo=
r some time. The original thought came the idea that a damping plate was bei=
ng moved through a liquid -- why not move the liquid through the damping pla=
te. I have also studied the MET seismometer (I operate a CME MET vertical se=
ismometer in my home system) and have a moderate understanding of its princi=
pals and the electrochemistry involved.






I prefer the teleph=
one for detail discussion as I am not a good typist. I am from the old schoo=
l where a secretary did the typing so I am bit slow on the keyboard.



       I will let you into two secrets! Yo=
u can get programs to teach you to type! It took me about a week to get reas=
onably proficient.

       You can also get programs which tak=
e a microphone input and give you a printed word output....=20



       Regards,



       Chris Chapman