[volt-nuts] Old muirhead weston cell.
ed_palmer at sasktel.net
Mon Sep 13 04:11:26 UTC 2010
Did you remove it from a temperature-controlled enclosure? If not, it's
an unsaturated cell and 1.019XX V is correct. If yes, then it's a
saturated cell and the voltage is a little high. I have a couple of
Muirhead saturated cells that are spec'ed at 1.01877 V @ 15 C and
1.01859 V @ 20 C.
Eldon Johansen wrote:
> Hello, new guy here.
> I recently acquired an old fluke 801 differential voltmeter, and removed
> the Muirhead Weston cell from it.
> I'm not sure if it is the original cell or not, I don't doubt it.
> In any case, it was mounted upside down for what had to be a number of
> years, and there are several tiny balls of mercury loose.
> Compounding this issue, it does not work right side up, past 30 degrees
> from horizontal it is as if it turned off.
> My thoughts are this is due to the mercury detaching from the platinum
> wire, it works great lying flat on the table.
> In any case i took it to work last week and did some measurements,
> however the best i could do at the time is verify that it is delivering
> 1.0190 +/- .05mV volts.
> (This was at 18 degrees Celsius)
> I'm in the process of building an oil bath and temperature regulator for
> it, and by that time i should be able to find the 732b at work and get a
> more accurate measurement.
> My question is there any good reason why is it nearly half a millivolt
> over what the old books say it should be?
> Eldon Johansen
> eldon.johansen at gmail.com
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