[volt-nuts] Would you be concerned if the manufacturer does not have an uncertainty budget, so can't provide uncertainties in a calibration?

Dr. David Kirkby drkirkby at kirkbymicrowave.co.uk
Tue Apr 24 08:19:55 EDT 2018

On Tue, 24 Apr 2018, 05:37 Florian Teply, <usenet at teply.info> wrote:

> probably I didn't get my wording precise. Just as you say, it looks
> like they assume the resistors should have nominal value. Otherwise
> they would need to list what they assume to be the nominal value, which
> they don't. I was referring to the last column where they list the
> measured deviation of +0.0107e11. In any case, I would consider unknown
> resistances pretty odd as that would render the whole effort of
> having 8.5 digits in the first place useless... So the only
> explanation that would make sense is that the resistors should habve
> nominal values. Unless of course the have individual values from
> manufacture stored somewhere. But then it also wouldn't make sense to
> not tell the owner of the device...

The meter sent for calibration was a 4339B. That's a 5.5 digit high
resistance, not an 8.5 digit one.

> They don't spell out explicitlyy whether the test limits they give,
> i.e. here +/- 0.0573e11 ohms would be their own measurement
> uncvertainty or the instruments spec limits, but given the odd numbers
> I'd expect it to be their measurement uncertainty.
> Best regards,
> Florian

My interpretation is the numbers in the last column are the *difference*
between what Keysight believe is the correct value and what my meter read.
If you look on page 5, on Current Measurement Accuracy Test, you will see
for the 10 nA range, you will see test limits of +/- 0.063 nA and test
results of -.082 nA - so a failure.

The meter is going off to Keysight (UK) tomorrow. They may ore many not
send it to the USA, as they are waiting to hear from the USA whether they
can provide uncertainties.


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