Need help on calibration result analysis

Simplest thing would be to request they send you a report stating Expanded uncertainty. But, as their note stated; you still need to decide if it passes of fails, depending on your use.

Rachel said:

Unfortunately, they did not report pass/fail. Only a remark in their report: " The user should determine the suitability of the instrument for its intended use."

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I do understand. Rachel, do they say what the % of uncertainty is based on? Full scale? Or of reading?

BradM said:

I do understand. Rachel, do they say what the % of uncertainty is based on? Full scale? Or of reading?

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No, they didn't mention what the % is based on. I assume it is based on the mean measured value. They provided the Mean Relative Measurement Error % and Relative Measurement Uncertainty Interval (%) in the report. See attached pic.

Rachel, I'm sorry. I got nothing. I don't understand why that vendor is presenting the data that way without any further explanation.

I would just with the ±10% being within. However... there is this big "out of tolerance" posted on the certificate.
I would push them for more information, or send it to somebody else.

BradM said:

Rachel, I'm sorry. I got nothing. I don't understand why that vendor is presenting the data that way without any further explanation.

I would just with the ±10% being within. However... there is this big "out of tolerance" posted on the certificate.
I would push them for more information, or send it to somebody else.

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Hi BradM, thanks for the advice. I'm planning to send out this instrument to another lab for testing.

When you originally sent the instrument out fir calibration, did you state the standard that you required? In Europe it's probably ISO6789; if your calibration company could not provide you with a certificate that also confirmed pass or fail, then they shouldn't have accepted the item for calibration. They should be capable of calibrating within the permitted error and their measurement uncertainty.

For some of the comments that have been made regarding the calibration measurement being spot-on, because at 4cNm they have measured the exact value does not mean that this is the "true" reading. Calibration of torque tools is "interesting" to say the least.....

Wise decision to send it to another lab, but make sure that you specify the Standard against which you want it calibrated - and that you want a full certificate

Sorry, late to the party. Is this a torque instrument? What is the spec for the instrument; is it the 10% I see (that's very high for torque)?

So, taking a look at ISO 6789-2 2017, Part 2: Requirements for calibration and determination of measurement uncertainty, the evaluation of the relative measurement error is calculated in section 5.2 with examples in 5.2.1 and 5.2.2.

1. The sample mean (of sample size x) as measured by their standard is used for column 2 in Rachel's table. Since the sample mean equals the instrument set point, the mean relative error in column 5 should be 0% as far as I can see (((4 - 4) *100)/4). There may be computational errors or other source factors they are using.