Fluke 8558A/8588A 8.5-digit DMMs

[Kleinstein]

....
Why aren't there absolute specs on the 3458A datasheet? There is only a footnote that you should add 2ppm to be traceable.

At the high end the absolute specs are less important as the difference to the relative specs only reflects the cal lab quality. So it's only valid for the 1st year or so.  After that it depends on where and how the meter is calibrated. The extra 2 ppm  for tractability are only valid for the initial calibration at HP (this may have even changed over time).

[e61_phil]

....
Why aren't there absolute specs on the 3458A datasheet? There is only a footnote that you should add 2ppm to be traceable.

At the high end the absolute specs are less important as the difference to the relative specs only reflects the cal lab quality. So it's only valid for the 1st year or so.  After that it depends on where and how the meter is calibrated. The extra 2 ppm  for tractability are only valid for the initial calibration at HP (this may have even changed over time).

That might be clear to the people here in this forum section, but one can see many comparisions between Fluke 8508A and HP 3458A were people compare the specs from the 3458A datasheet against the absolute specs of the 8508A. And it is comfortable to have absolute specs which can directly be applied, that is what I expect from a "reference" meter. That doesn't mean they don't give relative specs.

[splin]

Very nice!
Do you know what kind of relays they use? The best ones I could find (thanks to Johannes!) are specified with 300nV typical. It seems that my box is better, but perhaps there are better ones..

Which relay are these? The COTO 3500 are < 500nV, that's the only ones I'm aware of with such low emf spec.

Panasonic TX-S

[EDIT] Take a look at this thread:

https://www.eevblog.com/forum/metrology/relay-choice-for-scanner/

[e61_phil]

Panasonic TX-S

Yes, I used Panasonic TX-S. They seem to work very well.

[EEVblog]

I've been told no on taking the lid off. They need the cal intact in order to send it to various customers over the coming weeks.
So I can have it tomorrow for the weekend, but can't do a teardown.
It might be available in December for that though.
Should I bother?

[Andreas]

What I do with every Instrument is a tilting test when having connected to a stable reference
E.g. here with a K2000 which is surprisingly bad (mostly due to the LM399 reference):

https://www.eevblog.com/forum/metrology/project-pimp-a-keithley-2000/msg1106829/#msg1106829

with best regards

Andreas

[daqq]

I've been told no on taking the lid off.

So, you're saying X-ray the crap out of it? 

[Kleinstein]

A longer run with a shorted input is definitely an interesting point. Kind of getting independent noise data that also include longer times (e.g. Alan variation curve).  There is little need to do this with many parameters. The main interest would be longer integration times, though very long times are very likely internal averaging. So something like 10 PLC would  be enough. For the voltage ranges, the 0.1 V range would sense mainly the input amplifier, the 10(20) V range would mainly sense the ADC part and the 100 V range and 1000 V range should not be very different, both having possibly quite some effect of the divider (unless they actually use different dividers.

For the noise I hope that Fluke did not include the same odd 0.1 Hz noise bump like many Keithley meters.

[laichh]

Good reading material about the Fluke 8588A:

https://arxiv.org/pdf/2205.11321.pdf

https://us.flukecal.com/literature/articles-and-education/electrical-calibration/application-notes/inside-newest-85-digit-re