George Bush wrote:

 > ...

> 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. 

    That article ia dated November, 1973. I've got the whole collection 
of Amateur Scientist columns on CD from . I 
think this is a great deal for $29 and recommend it highly, even though 
several of the early articles are just descriptions and pictures of 
amateur-made telescopes and how that hobby was growing at the time, with 
very little technical info. The articles in the most recent five decades 
more than make up for the earlier ones.

 > 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"
> 
> 	I appreciate the OP-amp survey that you are doing, it will really help in
> the construction of ametuer seismometers.
__________________________________________________________

Public Seismic Network Mailing List (PSN-L)