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Reply-To: "fred bartoli"
From: "fred bartoli"
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Subject: Re: Meter movements
Date: Mon, 18 Nov 2002 11:50:55 +0100
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Organization: Guest of ProXad - France
NNTP-Posting-Date: 18 Nov 2002 11:48:10 MET
Mike Monett a écrit dans le message :
> fred bartoli wrote:
> > Not at all Mike.
> > The opamp will force constant current into the meter movement. So its
> > driving impedance is infinite and there will be no damping at all.
> > You'll have to add the parallel resistor to damp the movement or to
> > a secondary feedback path from the top side of the meter. Don't have
> > find what the best compensation network should be but finding it should
> > almost straightforward.
> > Fred.
> Thanks Fred. I had come to the same conclusion after posting, but you beat
> to it:)
> I generally find the damping resistor by trial and error. Just place
> values across the meter and rotate it, then watch how the needle settles.
> the one that give the most pleasing response.
> The value doesn't seem very critical - changing it by +/- 10% has little
Yes of course, but it has on the meter sensitivity and possibly on the
overall tempco if the resistor value is too close to the movement resistance
I bet that a series RC (or something like that) as feedback from the meter
top to the negative input of the opamp could nicely do the job without the
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