Geoff,

Nope.  This one.

http://bnordgren.org/seismo/gif_images2.htm

Electrode resistances change very slightly with horizontal 
acceleration, which gets detected and amplified by a 
switched-capacitor circuit.
I think you might have been on Angel's FMES mailing list back four 
years ago or so.  That's what it is.

Brett

At 10:13 PM 8/1/2011, you wrote:
>Are you by chance talking about
>a float on water connected by lever
>arm to a potentiometer ?
>Possibly a strain guage of some kind ?
>i know there more to it than that,
>but this should be the basic idea ?
>
>geoff
>
>----- Original Message ----- From: "Chuck / Judy Burch" 
>To: 
>Sent: Monday, August 01, 2011 10:18 AM
>Subject: Pot and Tube Horizontal Seismometer
>
>
>>All,
>>I believe there is an error in the FMES spreadsheet just 
>>posted.  The correct natural frequency for a "pot and tube" 
>>tiltmeter/horizontal seismometer is:
>>(omega nought)^2 = ((3/2) g)/(2L +l(R^2/r^2)),
>>where g is acceleration due to gravity, L is height of liquid in 
>>the pot, l is length of the tube, R is pot radius and r is tube 
>>radius.  The complication is due to non-uniform speed of liquid 
>>flow in a tube, maximum at the center, zero in contact with the 
>>tube.  Steen and Casey, Theory of the Manometer Accelerometer, Rev 
>>Sci Instr, Nov., 1953, p1021-1028.  gives a complete derivation.
>>Chuck Burch
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