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Re: [Amps] Bird wattmeter

To: amps@contesting.com
Subject: Re: [Amps] Bird wattmeter
From: Peter Chadwick <g3rzp@g3rzp.wanadoo.co.uk>
Reply-to: g3rzp@g3rzp.wanadoo.co.uk
Date: Tue, 8 May 2007 12:02:21 +0200 (CEST)
List-post: <mailto:amps@contesting.com>
Gary said:
>I saw somewhere that the meter resistance is supposed to be 1400 ohms. The
ones I have measure 1399, 1406 and 1393 ohms.

The 1399 ohm meter reads about 10% low with 30 microamps thru it.
The 1406 ohm meter reads about 5% low with 30 micromaps thru it.
The other meter is way out in left field.

In one meter that I opened up it had a 200 ohm resistor in series with the
movement.<

My figure came partly from memory of that which I measured, but there is also 
the question of the measurement uncertainty, as I haven't given the DVM a full 
calibration for several years - which I ought to do.
73
Peter G3RZP
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