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Subject: A Diamagnetic horizontal seismometer
From: meredith lamb mlamb1@..........
Date: Tue, 30 May 2000 14:49:55 -0700

Hi all,

I finally constructed a horizontal diamagnetic seismometer with
eddy current damping.  It uses a levitated magnet mass, with
attached plastic spacers on each end.  On one end is a attached
Radio Shack "pill" neodymium magnet; which is centered over
a Hall sensor for output.  Its been fun messing with, but I
wouldn't recommend this approach....other than pure experimental
tinkering.  Realistically, one could roughly classify it as a
Shackleford/Gunderson type seismometer/pendulum, as the 
levitated mass simply hangs with reference to the overhead
ferrite magnets and other forces. For the moment there is no
magnetic shielding, nor any temperature maintenance circuitry,
and it only is inclosed in my normal "vault".  The Hall circuit
is the same as used with other S/G horizontal seismometers, less
the 10K output attenuation resister, on the same web page, and
for the moment, it maybe capable of 30 second response.  See:

and go to the "A Diamagnetic seismometer experiment", (it can
take afew minutes to load, and/or the "Diamagnetic comparison
graphs to other sensors" boxes, which for the moment only
contain acouple nearby quake records.  The graphs are GIF
images from Larry's Winquake program.  The results mostly
show more response to LQ or LR seismic disturbances. Naturally
it shows the larger bus and motor vehicle magnetic influences.
It doesn't seem to show the same short period responses as the
other comparison seismometers...but on the other hand, some of
the 5-10 second phases remain perplexing as too reason/source.

Credits for this experiment go to, Robert Lamb, John Lahr,
Dann Bartmann, Charles Patton and Martin Simon, for their
information and material assistance efforts.  Thanks guys!


Meredith Lamb


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