Expanded Uncertainty on Calibration Certificate

[Calibrationian]

Hello all,

Just wondering on reporting of expanded uncertainty.
As per our calibration lab partners' certificate, every test points have their own expanded uncertainty values... some have the same values though but some have individual different expanded uncertainties.

On our own certificates, some have a common uncertainty budget on the same parameter/unit using the maximum of the standard deviation errors...

The one who made this budget has more training and experience than me so, I can't decide if this is wrong...
Please help... Thanks

 

[dwperron]

Hello all,

Just wondering on reporting of expanded uncertainty.
As per our calibration lab partners' certificate, every test points have their own expanded uncertainty values... some have the same values though but some have individual different expanded uncertainties.

On our own certificates, some have a common uncertainty budget on the same parameter/unit using the maximum of the standard deviation errors...

The one who made this budget has more training and experience than me so, I can't decide if this is wrong...
Please help... Thanks

A lot will depend on the expectations of those you are calibrating instruments for. Yeah, it is a lot easier to just assume the worst case scenarios and accept a larger measurement uncertainty, and sometimes that will be adequate. For instance, if you are calibrating a 3.5 digit DMM with a 5520A then you can use the worst case number for all ranges and it works OK. But if you are looking at a 6.5 digit DMM than your TUR will go real close to a 1:1 ratio, or beyond, which to most is unacceptable.

You maty not care about your reported uncertainties, but if I am using your calibration cert numbers then that is what I start from when I compute my own uncertainties. Your high uncertainty will force my uncertainties to be even higher, and in most cases I would not find that acceptable.

The labs who go through the effort to produce the real uncertainties for each measurement point typically produce much better measurement uncertainties than your method, in the calibration world that is huge.

 

[Calibrationian]

A lot will depend on the expectations of those you are calibrating instruments for. Yeah, it is a lot easier to just assume the worst case scenarios and accept a larger measurement uncertainty, and sometimes that will be adequate. For instance, if you are calibrating a 3.5 digit DMM with a 5520A then you can use the worst case number for all ranges and it works OK. But if you are looking at a 6.5 digit DMM than your TUR will go real close to a 1:1 ratio, or beyond, which to most is unacceptable.

You maty not care about your reported uncertainties, but if I am using your calibration cert numbers then that is what I start from when I compute my own uncertainties. Your high uncertainty will force my uncertainties to be even higher, and in most cases I would not find that acceptable.

The labs who go through the effort to produce the real uncertainties for each measurement point typically produce much better measurement uncertainties than your method, in the calibration world that is huge.

Hello sir,
Thanks, will do the individual report of uncertainties then...

On a side note the instruments we calibrate with "worst case" uncertainty reports, are not used to calibrate other instruments. They are simply test instruments for measurement purposes only...