"Charles R. Patton" wrote:

> Second:
> Meredith Lamb asked, “…questions involving using the neodymium magnet as
> a seismic sensor…”
> I knew for a long time that a carbon rod had been incorporated in a
> seismic sensor but I didn’t know much more until recently I finally
> found the report with the construction details.  ARPA sponsored Arthur
> D. Little company to design a borehole seismic sensor around 1967-69.
> The final report is titled:
> DEVELOPMENT OF A THREE-AXIS LONG-PERIOD SEISMOGRAPH
> Report no. C-69429.  It’s a 75 page report with many of the construction
> details.  It used a 2.5” by 0.086” dia. carbon rod approx. 0.8 gms in
> weight suspended diamagnetically as the seismic mass.  They sensed the
> position photoelectrically.  The sensor itself was essentially flat from
> DC to 0.5 Hz.  With filters they tailored the response to be flat (3dB)
> from 0.02 to 0.07 Hz. teleseimic events of mb <= 5 were consistently
> recorded.  You can order it from NTIS at 800-553-6847 for $34.  (It’s
> public domain, and if you want a copy from me I’ll do the whole thing
> for $10, US postage included.)
>
> Sincerely,
> Charles R. Patton
> charles.r.patton@........
>

Charles,

This news is absolutely amazing to me.  I would almost suspect the
construction details are pretty much beyond any amateur level to
accomplish; but they would sure be very, very interesting to see.

In a way, I thought diamagnetic suspension only occurried in
the 1990's....but, from John Lahr's site and reference followup,
there is some implied reference (unaccessible for the moment), with
dates going back to the 1940's.

Thanks so much for the information.

Meredith Lamb






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