These are both what we in exploration geophysics would call refraction
seismographs.  You use them with a sledgehammer energy source and a =
single
geophone.  You hit an aluminum plate located distance x from the =
geophone
and measure the time required for the P waves to get to the geophone.

Then you move out 2x and repeat the experiment, and then 3x and so =
forth.
You draw a graph of time vs distance.  As you go further out, the waves
travel down through harder layers (because it's a quicker path) and the
slope of your line changes.  Typically there will be 3 or more layers, =
e.g.
soil, weathered rock, clay, or water table, and then bedrock.  From the
slope of the line on the graph you can calculate velocity, which tells =
you
something about the type of material.  From the intercepts, you can
calculate depth.

You can download a manual on engineering seismic at
ftp://geom.geometrics.com/pub/seismic/Literature/s-tr2.pdf

If the link doesn't work, go to
http://www.geometrics.com/Literature/literature.html register and look
around for the Redpath book and other interesting stuff.

The Geometrics unit is I think still supported. I'm not sure about the
Soiltest unit. You would need some accessories to use it, a hammer =
switch, a
geophone, a metal plate, and a way to charge the battery. I was a =
founder of
Nimbus Instruments, so I could offer advice.

The soiltest unit looks complete.

Doug Crice          http://www.georadar.com/geostuff.htm
Wireless Seismic            http://www.wirelessSeismic.com
12996 Somerset Drive                phone 1-530-274-4445
Grass Valley,  CA  95945  USA    fax 1-530-274-4446
=20

-----Original Message-----
From: psn-l-request@.............. [mailto:psn-l-request@............... =
On
Behalf Of BOB BARNS
Sent: Sunday, March 20, 2005 8:05 AM
To: psn mail
Subject: 2 ebay auctions

Nimbus Instruments signal enhancement seismograph ES125	 Item number:=20
7502065715	ends Mar 26

SOILTEST PORTABLE ENGINEERING SEISMOGRAPH MD-5 SURVEY	 Item number:=20
7502107292	ends Mar 29

I know nothing about these.
Bob

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