[HomeBrew] Re: EMF meter?

[W1EOF]

You had the meter on AC-low voltage range? I would think that would work.
Most feild-strength meters use a germanium diode (low v-fwd) and a small cap
to rectify the resulting voltage. Then feed that through a pot to a
micro-ammeter. Say 50 or 100 micro-amps full scale.

But I would think they are more interested in a electrostatic charge meter.
A bit more complicated... basically it's a very, very... very high impedence
voltmeter. Look up "electrometer" on Google and you'll find some circuits.
To make a good one requires some special ICs, resistors (for the feedback),
and good construction techniques. Not very expensive but if not made
correctly it will never work.

73,

Mark W1EOF

> Message: 1
> Date: Sun, 06 Nov 2005 09:01:00 -0500
> From: Dan K9ZF <n9rla at yahoo.com>
> Subject: [HomeBrew] EMF meter?
> To: homebrew at mailman.qth.net
> Message-ID: <436E0C9C.2040906 at yahoo.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Good morning all,
>
> I have a friend to fashions himself to be an "amateur ghost hunter".
> One of the gadgets they use for this is an EMF meter.  He knows I, being
> a ham,  enjoy building all manor of gadgets, so he asked if I could
> build him one.
>
> I gave it some thought, and figured it should be simple.  We want to
> detect fields, so what I need is a big coil hooked to a volt meter....
>
> So I found a roll of old telephone wire in the junk box.  [probably
> 20-24 g, insulated, stranded]  I wrapped about 100 turns on a piece of
> 3/4" pvc and hooked it to a DVM.  I then waved it by a florecant shop
> light to test it, and got nothing....
>
> What am I missing?
>
> Thanks,
> Dan
>
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