Please assist me to interpret the standard with regards to making the clear distinction between VERIFICATION, CHECKING, and CALIBRATION. I have always sent the Master device to outside calibrators and obliviously state on the purchase order that ‘measurement standard to be traceable to International or national standard or any other suitable controlled master’. I then use the calibrated Master device to verify other internal devices in usage to validate the measurement result.

I had a lengthy debate with a colleague; he argues that a check by devices in usage against an uncalibrated Master device is acceptable. He states that there is no requirement in the standard to carry out calibration on the device including the Master device. Please advise how the standard is interpreted regarding the above.

I don't understand if your colleague has looked at 7.6 and ISO 10012-1?
a) be calibrated or verified at specified intervals, or prior to use, against measurement standards traceable to international or national measurement standards ; where no such standards exist, the basis used for calibration or verification shall be recorded;
But, the debate, couldn't be started for the misunderstandig about the selection of the devices that you have to calibrate? Or not :bigwave:

As for...."making the clear distinction between VERIFICATION, CHECKING, and CALIBRATION"... There is no clear distinction in the definitions and the terms tend to be thrown about interchangeably. I have a clear idea about what I am sure of each of these means but I have run into many others as sure in their convictions with different ideas. The definition of these terms was discussed at the A2LA Conclave this year. In the end, there was no resolution.

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When someone claims to be an expert and has the absolute correct definition of these terms, they are stating only what they believe, which is worth as much as any other opinion.

As for your equipment, I don't see how your colleague's argument holds any validity and I don't even know what the standard is. Depending on the stability, history, etc., it should be check at least once (with traceability yada yada yada).

There is a simple answer. VIM (International vocabulary of general and specific terms in metrology) puts a requirement on calibration that it have (1) an unbroken chain of comparison to National or international standards, and (2) stated uncertainties at each step.

That is calibration, internal or external.

Checking and verification are effectively the same, in that you are checking the whatever to verify it against a standard.

That is NOT calibration.

Hope this helps.

Hershal

Checking and verification are effectively the same, in that you are checking the whatever to verify it against a standard.

That is NOT calibration.

Checking a "whatever" to verify it against a standard is calibration.

If it is an unbroken chain of comparisons AND you calculate the measurement uncertainty, then I might agree with you.....

Typical shop checks do not include calculations for measurement uncertainty however.

Hershal

Checking a "whatever" to verify it against a standard is calibration.

So your stating that a ruler can be "calibrated". What actions can be taken to "calibrate" a rule?

I understand that we're talking semantics, but I have always associated "calibration" with making adjustments. On the other hand, verifications (checking) are comparisons against a standard where an item that can be "calibrated" is then adjusted, and one that can't (as in a rule) is replaced as required.

So your stating that a ruler can be "calibrated". What actions can be taken to "calibrate" a rule?



I understand that we're talking semantics, but I have always associated "calibration" with making adjustments. On the other hand, verifications (checking) are comparisons against a standard where an item that can be "calibrated" is then adjusted, and one that can't (as in a rule) is replaced as required.

Don't underestimate the importance of semantics. It's critical that we all understand what we're talking about, and if the standard denotation of a word has been given a different contextual connotation, there's danger of misunderstanding. In our work--especially in automotive and aerospace applications--"calibration" might involve more than just comparison to a standard, as Hershal points out in referring to MU and traceability (although traceability is a requirement for calibration rather than part of the definition).

Even with the special definition though, calibration does not necessarily involve adjustment. What happens if a device is due for calibration but no adjustment is necessary? The fact that it's been compared to the standard means that it has been calibrated. You wouldn't take it out of service because it didn't have to be adjusted. The ruler isn't the best example because no adjustment is possible. That doesn't mean that rulers shouldn't be in the calibration system. The typical procedure involves an initial verification of the scale and subsequent periodic verification that the scale is still legible and that there hasn't been any damage that might affect measurement accuracy.

The first question about rulers is can they be calibrated? Yes, since calibration is an unbroken chain of comparisons to national or international standards, and the measurement uncertainty is staed at each step.

The real question is why in the world someone would calibrate a ruler.....with the possible exception of the finest metal ones, or NIST's new nano-ruler.

Hershal

The real question is why in the world someone would calibrate a ruler.....with the possible exception of the finest metal ones, or NIST's new nano-ruler.HershalLOL - I have 2 calibrated rules in my lab, and I had them certified when ordered from Starret. They do not have a recall on them; therefore, it was a one time calibration "check". Personally, I think it's silly also, but try communicating your rational to auditors that don't understand metrology.

Been there, done that.....

No win situation....

Hershal

Firstly, I would like to apologize for the lack of prompt response on my side due to the fact that I was on holiday. Thanks for every post that the thread has received. I have now managed to convince my colleague that he indeed misinterpreted the standard in this regard. The standard states that “equipment shall be calibrated or verified…… against measurement standards traceable to international or national measurement standards: (AND ONLY) where no such standard exist, the basis used for such calibration or verification shall be recorded.” Therefore, checking or verification equipment against unknown traceable international or national measurement standard is unacceptable unless where no such standard exists.

I hope this post will not deviate from the topic. Does anyone of you have a sample of calibration procedure which clarifies the difference between the ones you've been discussing in this thread, verification, checking and calibration (looks like a "calibration", the right word) ? I will be doing a lot of procedures to comply with ISO13485 and I was wondering if someone can ease my workload? Thanks in advance. :rolleyes:

I am not aware of any procedures that specify the difference, although besides the VIM, there may be some further information on the differences in the Metrology Handbook or the USAF PMEL Handbook.

Hershal

How about just the calibration procedure itself?

How about just the calibration procedure itself?Maybe not perfect, but a start. Of course you must tailor it to your organization and needs.

Again....thanks Al, yup I'll just use this as reference since we have a web system that includes calibration center !!! I got more sample procedures here in the cove....and try to consolidate these and create our own procedure. :agree1: