Cal labs for 3458A and their uncertainties

[e61_phil]

Quoting the calibration uncertainties at 99% level sounds weird when most of the stuff is quoted at K=2 95% level but I'm too lazy to check what ISO 17025 has to say about it.
(stability specifications are often quoted at some other level)

I thought (without any evidence) Fluke sticks to their 99% levels. The old instruments (5440B, 5450A..) are only specified at 99%. Only the "newer" ones has additional 95% specs to be comparable with other equipment.

Both Keysight and Fluke in US have their own Josephson standards, apparently Fluke Deutschland also has one and guessing from uncertainties I'd say that Fluke Norwich also have their own.

The next calibration of our 8508A will take place in germany, I think.

[mzzj]

The next calibration of our 8508A will take place in germany, I think.

https://www.dakks.de/as/ast/d/D-K-15123-01-00.pdf
Looks to be "good enough" at 0.2ppm for 10volts

[mzzj]

And one way to look for ISO 17025 certified labs is from the ILAC-MRA website:
https://ilac.org/signatory-search/

Select for example Germany and you get link to DAkkS website with a list of all accredited calibration labs in Germany. Still takes some time to skim trough their CMC (calibration and measurement capabilities) "scope"
When you select accredited lab you can also trust to the results more... unless its US lab. Those goddamn luddites are still not able to grasp the idea of "total calibration uncertainty" even if they are accredited 17025 lab 

[Henrik_V]

...
The PTB stated 3ppm for their 3458A on the Maker Fair 2018 for 10V range, as far as I could find on www.mikrocontroller.net.
...

-branadic-

NO.... never ever ..  not at the fair.  The 3458 had been calibrated UNDER LAB CONDITIONS to the cited 3ppm.  They might have performed better, but don't deal serious ppm at a fair  ... thats not faire  äh serious. 

For uncertainties there are databases the CMCs at the BIPM for the national laboratories and at  DAkkS for the german ISO 17025 labs. Same can be found for other nations.  Just keep in mind that the stated uncertainties migth not be the 'standard' uncertainties you get for the standard price
 

[mzzj]

  Just keep in mind that the stated uncertainties migth not be the 'standard' uncertainties you get for the standard price
 

Much true.
And the CMC values are sort of "ideal case" when the meter under calibration is enough good/stable.  You can get  different uncertainties for two different 3458A meters from the same lab.

[Moon Winx]

Quoting the calibration uncertainties at 99% level sounds weird when most of the stuff is quoted at K=2 95% level but I'm too lazy to check what ISO 17025 has to say about it.
(stability specifications are often quoted at some other level)

I thought (without any evidence) Fluke sticks to their 99% levels. The old instruments (5440B, 5450A..) are only specified at 99%. Only the "newer" ones has additional 95% specs to be comparable with other equipment.

Both Keysight and Fluke in US have their own Josephson standards, apparently Fluke Deutschland also has one and guessing from uncertainties I'd say that Fluke Norwich also have their own.

The next calibration of our 8508A will take place in germany, I think.

It's confusing, but maybe this will help clear it up.

Fluke uses 99% CL in their manufacturing quality control and so the guaranteed specifications are presented at the 99% CL (for a great explanation of this, see http://download.flukecal.com/pub/literature/msc04.pdf).

The 95% specifications are listed due to contract obligations from a specific organization that requested published 95% specifications as a requirement in order to buy the calibrators.

Don't use the 95% specifications unless your supporting lab verifies the calibrator to the 95% specifications. Why? Because if you have a unit that is out of tolerance and needs repair, you may send it to Fluke, who, by verifying it at 99% specs, may not see a problem.

The confusing part is that labs use measurements with uncertainties presented at 95% to compare to Fluke's 99% test limits to determine pass/fail. It's confusing until you are convinced of the fact that your measurement uncertainty CL has nothing to do with the CL of the specifications you are comparing against.

If Fluke's 95% published specs were proportional to the 99% by a constant (they are not), you *could* use the specifications @ 95% even when tested at 99%. But until someone from Fluke clears this up, I"d avoid the 95% listing altogether.