PSN-L Email List Message

Subject: Hi all.
From: "Eric D. Fehr" fehr@............
Date: Fri, 10 Mar 2000 19:55:38 -0700

I just joined the list on Sunday, and would like to briefly introduce
myself, and ask for some input.

I'm from Alberta, Canada, and will be moving to the Bay Area soon to work
for SegaSoft (well, OK, I was supposed to move in November, but who ever
said getting a work visa was easy.)  This move has prompted me to take a
more active interest in seismic activities.  I now have an irresistible
urge to build things seismic (to the disdain of my wife).

I have enough of a history in electronics to build and circuitry, etc, to
drive the hardware, but I am trying to decide what would be the best type
of sensor equipment to use.  I wanted to build a Lehman sensor, but my wife
vetoed it, due to size.

Currently I am looking at possibly a geophone configuration, or a force
balance accelerometer (if price is not prohibitive).  A SG seismometer is
also a possibility (or a modified design that I have been working on in my
head - I have a preference for non-RF electronics).

Does anyone know an approximate price for a decent FBA sensor (1-3 sensor -
I'm guessing mega $ here...)?  I have already contacted geospace for a
quote on the GS-11 geophone, so I know what price range I would be looking
at for that.  I could also try a few more local surplus stores, as seismic
surveys are quite active throughout Alberta.  However, I have had no luck
at any of these stores yet.

I also have not seen any discussion anywhere on using an integrator in
combination with a geophone.  I would think that a geophone -> preamp ->
low pass filter -> high pass filter -> integrator -> amp arrangement could
be fairly sensitive for low cost, but would like to know some opinions
about if it would be worth trying?  If the high pass filter cutoff
frequency were at aprox. 50-80% of the resonant frequency of the geophone,
I would think that you could pull up low-end performance without inducing
too much noise (from looking that the performance specs for the units).

Well anyway, I seem to have rambled on enough for now, so till later,


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Larry Cochrane <cochrane@..............>