From: John Honniball <coredump_at_gifford.co.uk>
Date: Thu Aug 19 19:21:34 2004

Tony Duell wrote:
> 'A potentiometer-wire voltmeter is better than a DMM because the former
> draws no curret at balance'. This is more subtle. While it's true that a
> potentiometer-wire voltmeter dwraws no curret at balance, you can never
> know it's exactly at balance. You are limited by the sensitivity of the
> detector you're using. And when that detector is a moving coil/pointer
> (not a mirror) type of meter with a sensitivity of, perhaps, 1uA if
> you're lucky, then a 10M ohm DMM actually takes less current from, say, a
> Weston standard cell.

I heard that argument for the superiority of the potentiometer at
school, too. It would've been in about 1979. Wish I'd thought of
the counter-argument about the sensitivity of the meter, but I
didn't think of it until many years later.

John Honniball
Received on Thu Aug 19 2004 - 19:21:34 BST

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