Hello everyone! As some of you know, I have a calibration lab and I enjoy testing voltage references and have dabbled with creating my own. However, after perusing the threads here, I see that my efforts have been eclipsed by some epic efforts by the likes of Dr. Frank, Andreas, Branadic, TiN, et al. I have several Fluke 732 references. One of my older units, a 732a has an extraordinary drift history. I measured it once with a Keysight 3458a that was right back from a metrology lab calibration from Keysight (compared with their Josephson array) 20 months ago, and once again recently with the same meter back from another metrology grade calibration. The result: 0.3ppm difference! Yes, the temp/humidity was the same for both measurements, same cable connecting the units, RF field measured, ACAL ALL, 200NPLC, etc,, etc,, etc. An incredible result. Of course, if we apply all the uncertainties, a cynic can say that this is hardly definitive proof. Well, I concede that point, but now I have 2 more 732a units, a 732b, and 732c which will give me really good data points in the coming years.
So, sorry for the long winded intro, but my question is this: Who has the best reference here? I mean one that they've built. Also, you have to back up your claims by comparisons to a known voltage reference such as the 732. I have 4 3458a meters sitting on my bench right now and can see them drift over the course of 24 hours by 0.3 to 1.6ppm max difference between them.
Looking forward to your responses!
TomG.
My apologies for forgetting Kleinstein!