Re: [volt-nuts] Old Weston cells
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.
Re: [volt-nuts] Old Weston cells
pa4...@gmail.com writes: 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. I have that same unit myself. For some years I kept it on and would periodically compare the cells to my (calibrated) Datron 4910's. I kept logs of the voltage sampled weekly using an 8.5 digit meter for differential comparison for 2 or 3 years. I was surprised at how stable and predictable they were. But, I stopped doing that probably 5 years ago. Nostalgia strikes, I'll plug it back in and see what's changed. Unfortunately, it takes weeks for the voltage to stabilize from a cold start. -- Bill Ezell They said 'Windows or better' so I used Linux. ___ 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.
Re: [volt-nuts] Old Weston cells
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-boun...@febo.com [mailto:volt-nuts-boun...@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 ___ 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.
Re: [volt-nuts] Old Weston cells
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 jlt...@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-boun...@febo.com [mailto:volt-nuts-boun...@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 ___ 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.
Re: [volt-nuts] Old Weston cells
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.
