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>Posted on 19 Oct 1996 at 14:14:45 by Harold Gartner


>Does anyone on the list have experience in building their own magnometer
>for use in finding wrecks in the 200-300fsw range?  If so, where can one
>look for plans etc. for this type of gear as opposed to just buying a
>Fisher unit for 7K?


Care to describe the 7k Fisher unit in some detail ?
How do you "fly" it and what sensor does Fisher deem
sufficient for this application ?


I'm no expert on this but I do find the topic
interesting and worthy of some on-line exposure.


You might want to look into fluxgate sensors and the
related resonant fluxgate type.  Both typically utilize
a tape wound magnetic core (specialty material) and
some two thousand precision laid windings of Cu
on that core which kind of dictates that you buy the
sensor rather than attempt to make one if high sensitivity
is a goal.


A potentially better and still affordable sensor has
become available: the variable permeability sensors.
If you are up for an experiment I suggest you look into
these.  The associated electronics isn't that hard to
do.


Now if you decide to push ahead I think you'd want
to plan for three sensors to cover all three axis
because you might want to monitor the vector-summed
output of all three orthogonal sensors rather than
go nuts every time the submerged probe tilts in the
earths background field.

I jokingly suggested to someone else in private e-mail
that why not look into a DIY side-scanning sonar.  Seems
to me alot of the hardware work will be similar though.


Regards,
John.

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