Calibration certificate

[Irv1n]

Can someone help me with question?

I have calibration certificate on Fluke 5720A. In certificate point of calibration 100 mV; 1V; 10V; 100V; 1000V with uncertainty 95%. If i need calibrate something with this calibrator on point 8 V or 27 V (or any points) can i use uncertainty from certificate (interpolated values?) or need use only specification from user manual?

[briansalomon]

No. Even for a basic estimate of uncertainty you need more information.

In order to be of service to your customers on this subject some reading is required.

Here is a link to one. http://redsang.ial.sp.gov.br/site/docs_leis/im/im6.pdf
It's only 42 pages long and you should be able to read it over the weekend.

It has links to other related sites as well.

[Irv1n]

No. Even for a basic estimate of uncertainty you need more information.

In order to be of service to your customers on this subject some reading is required.

Here is a link to one. http://redsang.ial.sp.gov.br/site/docs_leis/im/im6.pdf
It's only 42 pages long and you should be able to read it over the weekend.

It has links to other related sites as well.

I know what says this manual. I know about about repeatability, reproducibility, drift resolution and other contribution uncertainty. My q was only about situation when customer request specific point that i not have in my calibration certificate.

[briansalomon]

The tolerance for the standard you're using has a specification for the ranges and functions you're being asked about. That specification is part of the answer to your question.

How detailed we get with our estimates can be a touchy subject. I usually use what the customer is doing with the equipment as at least part of my rationale for how detailed the estimate is.

[RFCAL]

You need the uncertainty for those specific set points. You need to calculate your own uncertainties and you should be calculating YOUR uncertainty budgets using a range. I.E. DCV 0-100mV range. That way, you can cover the 50mV set point. The Uncertainty Calculator from Quametek allows for a range calculation. You can slide the bar up and down within that range and find any set point uncertainty.

[NC-Cals]

I agree with RF cal on this one. It is impossible to get calibration uncertainties for every data point you are going to use. Interpolation is a reasonable method to ESTIMATE your uncertainties. Remember, these are estimates, not exact values. If you are uncomfortable interpolating the uncertainty, then use the larger of the two calibration uncertainties. This would be the the most conservative approach to making the measurement uncertainty calculation.
I disagree, however, with including the client's application as a consideration of how detailed the estimate should be. The uncertainty is the quality of your calibration, not what it is used on.

[briansalomon]

I agree, it is a statement of my own calibration.

I use ISG Uncertainty Analyzer for formal estimates of uncertainty. Using that software, it can take quite a few man hours to render an estimate.

If they're using a DMM for troubleshooting I think it's reasonable to give an abbreviated estimate of uncertainty as long as it's valid and accurate.

That said, I do work in a small commercial lab and I understand the quality standard for each lab can vary.

[NC-Cals]

I use uncertainty toolbox and, it too, can be really time consuming. The amount of work required to give statements of uncertainty for each measurement can really add up to an unneeded expense - especially for a small calibration lab. I understand it for your top tier calibration labs, but I will never understand a user needing the information for a process calibration. What is their return on investment when they pay extra for an ISO Accredited calibration?

[briansalomon]

Very few people use the data. When my 5500A current function went out of tolerance I did look at the data Keysight gave for my 3458A just to make sure where my measurement was but I didn't use it in my report because it wasn't needed.

I've used the data from one RTD and a few other standards but not often.

Customers need accredited certs and they are asking about uncertainty because ISO is driving them to do that in order to get contracts.

Automating the process of estimating uncertainty is probably the solution.

[Irv1n]

Ok! i have example:
I calibrate DC Zener 732B. And nanovloltmeter show the difference between standard and calibrating DC= 213 nV; 215nV; 217 nV (repeatability) on Range 1 microVolt. What uncertainty i need use in budget for nanovoltmeter?

[RFCAL]

You have to calculate this using the unc of the 732B , DMM , and the 5720A. We can't give you the answer.