[Rockhounds] metal detector question

[Gene Jeffers]

Excellent article!  I would add that VLF detectors usually include a
mechanism for "ground balancing". In even moderately mineralized soil, the
evenly distributed metallic or metallic oxide content in the soil reacts to
the magnetic field produced by the transmit coil as the detector head is
raised or lowered in relation to the ground. Ground balance circuitry can be
manual (a potentiometer) or automatic (microprocessor controlled) and
adjusts the receive coil to compensate for the magnetic field produced by
the ground mineralization reacting to the magnetic field generated by the
transmit coil. Without this "ground cancellation", it would be virtually
impossible to find coin sized objects in moderately mineralized soil. BFO
type detectors do not have a mechanism for ground cancellation and are
generally only useful at beaches or areas of very low metallic content.
Likewise for PI type detectors which seem to be mainly used for salt water
treasure hunting and little else.

-Gene
----- Original Message ----- 
From: "Kreigh Tomaszewski" <Kreigh at Tomaszewski.net>
To: "Rockhounds at drizzle.com: A mailing list for rock and gem collectors"
<rockhounds at lists.drizzle.com>
Sent: Sunday, February 03, 2008 8:41 PM
Subject: Re: [Rockhounds] metal detector question


> Glenn Wimpee wrote:
> >
> > Hey Ron,
> >
> > Your original question was how do the detectors work.
> >
> > I have not seen a good response to that, so I'll share MHO.
>
>
> Check out http://electronics.howstuffworks.com/metal-detector.htm
>
> Kreigh
>
> -- 
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