Re: [volt-nuts] The averaging reference
The Datron 1081/1082 are 7-1/2 digit meters. The zeners are two pair of two zeners in series to get the ref voltage up high enough. In the two 1081s I had, they worked quite well, ref’d to the two Fluke 732As I had at the time. But not 8-1/2 digit grade, I don’t think. I have no idea what the 127x/128x sereis use; probably the LTZ1000A... ___ 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] The averaging reference
Jan, Thanks for a good summary f the pros/cons. Of course the LTZ1000 is much closer to the current state of the art, but the REF102 is far easier to use and to calibrate. I'm definitely not shooting for sub-ppm performance, if I can build anything that stays within (say) 20 ppm long-term, that would be more than adequate as a home standard. I wasn't aware of the degraded long-term drift performance in the plastic packages, as compared to the metal can. I'm surprised they can't protect the chip from package-induced effects! One thing I don't like about the LM199 and LTZ1000 is that although they are stable, they are sold uncalibrated. As a result, building a 10-V reference with either of them would require at least two very stable resistors, one of which must be selected within a range of several percent to get an accurate 10V output. Most of the DVMs I have seen with the LM199 / LTZ1000 use soft calibration in which the calibration coefficient is stored in memory, and the voltage measurement is performed in ratiometric mode. Building a 10V reference is a rather different problem. As before, comments and suggestions will be welcomed! Joel Setton On 19/12/2014 19:28, Jan Fredriksson wrote: It's no coincidence that virtually all 8.5 digit DMMs use the LTZ1000. It's in a class of it's own. REF102 is not in the same class, even if you average a handful. But there are a couple of nice things about the REF102, though for more moderate requirements - You get a reference at 10V, +/-0.0025V, trimmable (not a 5% 7V of the LTZ1000) - Moderate power / current - Low sensitive to supply voltage - Very simple to implement There was a metal can version but it's obsolete. But be aware that the TI site still shows the metal can spec 5ppm/1000h while the available packages are actually 20ppm/1000h! ___ 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] The averaging reference
I believe the 1281 uses the LTZ1000. The datasheet mentions dual references. My 4920 has both a ltz1000 and a lm399. I think you can find pics of the 1281 dual ref setup on eevblog. I would not be surprised if the 8508a has a similar configuration. Todd On Saturday, December 20, 2014, Richard Moore richiem5...@gmail.com wrote: The Datron 1081/1082 are 7-1/2 digit meters. The zeners are two pair of two zeners in series to get the ref voltage up high enough. In the two 1081s I had, they worked quite well, ref’d to the two Fluke 732As I had at the time. But not 8-1/2 digit grade, I don’t think. I have no idea what the 127x/128x sereis use; probably the LTZ1000A... ___ volt-nuts mailing list -- volt-nuts@febo.com javascript:; 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] The averaging reference
On 20 Dec 2014 21:18, Joel Setton set...@free.fr wrote: Jan, Thanks for a good summary f the pros/cons. Of course the LTZ1000 is much closer to the current state of the art, but the REF102 is far easier to use and to calibrate. I'm definitely not shooting for sub-ppm performance, if I can build anything that stays within (say) 20 ppm long-term, that would be more than adequate as a home standard. One thing I don't like about the LM199 and LTZ1000 is that although they are stable, they are sold uncalibrated. As a result, building a 10-V reference with either of them would require at least two very stable resistors, one of which must be selected within a range of several percent to get an accurate 10V output. I suspect if you built something very stable using an LTZ1000, it would be possible to get one or more volt-nut with a 3458A or similar to measure it for you. You could even average the result from several volt nuts. Dave. ___ 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.
