PSN-L Email List Message

Subject: Re: Op amp front end noise
From: John Popelish jpopelish@........
Date: Sat, 12 Mar 2005 13:55:04 -0500

George Bush wrote:
> John Popelish wrote:

> >I am interested in how the tiltmeter
> >connects to the amplifier. 
> It uses RF connected to the mercury to excite antenna plates just above
> two connected pools 24" apart. The antenna signals are detected (rectified)
> and fed into the INA121 in a differential configuration. The DC impedance
> is high (back impedance of the diodes), but since they are charging .1 uf
> caps, the AC impedance is low. The mechanical design is old and originally
> appeared in an early 1970's "Scientific American" Amatuer Scientist article
> "A Sensitive mercury tiltmeter that serves as a seismometer". I still have
> a copy of the pages (pp. 124-129), but SA didn't print the date on the
> pages. Recently Ron Newton modernized the electronics and published an
> article on the May 2003 "Nuts n Volts" magazine, pp. 47-51, "Measure Earth
> Tides with a Tiltometer"

If you have a scanner, I would very much like to get a look at those
I have a big email inbox.  Perhaps we can get permission to copy them
on a web page.

John Popelish

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