These are the type made to put in portable equipment. That should be the unsaturated type, correct?
Joe Gray W5JG On Tue, Aug 27, 2013 at 12:08 AM, <pa4...@gmail.com> wrote: > 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. > _______________________________________________ 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.