Are you sure they are unsaturated ? Because most unsaturated cells last only 10-20 years (AFIK). Saturated cells last much longer but they should be kept at 30 degrees celcius for the correct value. On the other hand, as far as I know they do not survive if they are not kept vertical and most of the time they are not when they are kept outside their oven.
I have 4 weston cells in a guildline cabinet with oven. I have the cal data for the first 10 years they have been used. After this time the oven was turned off , the lab was closed but all gear stayed put on that same place over 30 years (the lab was turned into a server room but all the gear just stayed unused ) I made a graph from the data. Took a ruler and extended the lines. After a few months I had a change to measure them with a calibrated 6,5 digit meter and a year later a 7,5 digit meter and the values I found where plus/min a few uV on the lines. But more important the difference between the individual cells was spot on with my graph. So I use them as my house standard (I do not measure them direct. I set my 332 at 10V. A fluke 720 of ESI KV at the value the cell must have. Connect them both to a Fluke 845 and set the 332 so the meter reads zero. Then I check my 731 against the 332 the same way and leave them both connected this way for a few hours. If the meter is still at zero after that time I use the 332 for calibrating a meter. The only problem is the high Rout of a KV. So I use a buffer made of a LTC1052 and LT1010 after the KV if the multimeter is a 10 M version. But I still wonder if that is needed. I tested it with some meters but did not notice a difference that was within the meters resolution. Fred, pa4tim Verzonden met Windows Van: Joseph Gray Verzonden: dinsdag 27 augustus 2013 06:26 Aan: Discussion of precise voltage measurement I suspected that there was nothing to do to rejuvenate these old cells. I thought I'd ask anyway. Thanks. Joe Gray W5JG On Mon, Aug 26, 2013 at 9:16 PM, zbigniew169 <zbigniew...@gmail.com> wrote: > All my knowledge regarding Weston Cells tells me that is not possible in > any way :-(( > > > 2013/8/27 Joseph Gray <jg...@zianet.com> > > > 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 > > _______________________________________________ > > volt-nuts mailing list -- volt-nuts@febo.com > > To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > > and follow the instructions there. > > > > > > -- > Zbyszek > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > > _______________________________________________ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. _______________________________________________ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.