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From: meredith lamb mlamb1@..........
Date: Sun, 13 Feb 2000 23:43:44 -0800

RADIOTEL@....... wrote:

> Meridith Lamb
> I appreciate the extensive infomation you provided regarding the hall sensor.
>  I have built a STM-8 basic seismo which is presently configured as a coil
> magnet unit (4 sec. period) since I am not presently skilled enough to tackle
> the electronics that Sean-Thomas's unit require.  I previously exchanged
> e-mail with Sean-Thomas regarding using the traditional SG electronics with
> the STM-8 of which he was encouraging for me to try.  However, it sounds like
> the hall effect approach would be almost a natural for this use and
> especially for someone with very limited electronics skills.
> Jim Allen
> Cerritos, Calif.


If I read you correctly in regard to using the Hall on the STM-8
frame, that will be most interesting to see how well it does,
besides helping elevate the electronics experience somewhat.
I also lack a lack a heck of a lot of experience....its just the
way it is.  I've never tried it on a vertical yet, but I think you
will see a more interesting increased "period".

One could also use a dual approach here, to make it even
more interesting.  Simply leave the coil/magnet as is, because
it will sense the nearby quakes P & S waves well.  After
building the circuit, add a very light extension on the same
seismo end for the Hall circuit; and that way you can get kind
of both worlds, the near by quakes and some more teleseisms
you wouldn't normally see very well with the coil/magnet.

Suggest building the circuit and getting used to it via a
tempory route of wires and hand manipulating of the magnet
near and far and from side to side.  It takes awhile to get
used to it, as its different than a straight amplifier where one
only adjusts the gain, filter or etc.  Of course on your seismo
the Hall would be mounted on the boom, with the 4 pole
magnet on the base frame.

To be honest.....(ha), I've shorted out more than just afew
diodes and capacitors with the wrong polaritys.

Take care,

Meredith Lamb


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