[volt-nuts] Old Weston cells

[Joseph Gray]

Sorry, no history at all. They were salvaged from old equipment. From what
I read, they are already below their voltage threshold and should be
tossed. I just thought it would be interesting to measure them anyway.

I think the decline rate was supposed to be around 0.08 uV per year, or
something like that.

After the 3457A is calibrated, I will try to track these three cells, even
though they are supposed to be no longer stable. It will be an interesting
exercise and will only cost me a bit of time. If the cells prove to be
unstable, I can always toss them later. I certainly won't be using them as
any type of standard.

I already acquired a Fluke 845A. It needs some attention, but seems to
mostly work.

Joe Gray
W5JG



On Mon, Aug 26, 2013 at 9:10 PM, J. L. Trantham <jltran at att.net> wrote:

> Joe,
>
> Do you have any data about prior measurements of these cells or their
> history?
>
> I read somewhere there is a predicted decline rate based on time and
> temperature IIRC.
>
> Once you get the meter calibrated, you can 'track' their measurements.
>
> Might also be time for a 'differential voltmeter' to add to the 'stable'.
>
> Joe
>
> -----Original Message-----
> From: volt-nuts-bounces at febo.com [mailto:volt-nuts-bounces at febo.com] On
> Behalf Of Joseph Gray
> Sent: Monday, August 26, 2013 9:59 PM
> To: Discussion of precise voltage measurement
> Subject: [volt-nuts] Old Weston cells
>
> I got my hands on a few very old, unsaturated cells. I figured that they
> would be no good after all this time. Just out of curiosity, I measured
> them
> on my 3457A, which hasn't been sent off for calibration yet.
>
> DMM was set to 3 V scale to keep the input impedance high. Room temperature
> = 26 C.
>
> Cell #1 = 1.018288
> Cell #2 = 1.018236
> Cell #3 = 1.018224
>
> I read that when they get below 1.0183 V, they are no good. Is there any
> (easy) way to rejuvenate these cells?
>
> Joe Gray
> W5JG
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