Is this Calibration or Verification ?

[PaulJSmith]

I have always tended to fall in line with Tara's and Sebastian's ideas of the definitions. However, I see the merit of Jim's explanation as well.

So, who's right?

 

[BradM]

For me gauge verification it is activity where we determine gauge error against standard and just leave it, as there is nothing more we can do. Use when error is within expected limit, scrap when outside. E.g. gage block.

For me calibration it is verification followed by adjustment, where we can move gauge error from area outside expected limit to area inside expected limit and then verify again effectiveness of adjustment. E.g. caliper (close jaws and when it shows 0,01 simply press "Cancel" or "Zero", then open and again close jaws and check if it shows 0,00)

I see some similarity to rework of nonconforming product.

And... you're correct too!!

But seriously, it doesn't take long to figure out how confusion can abound.
That's why it really important to have the definitions clearly defined within your system.

 

[BradM]

I have always tended to fall in line with Tara's and Sebastian's ideas of the definitions. However, I see the merit of Jim's explanation as well.

So, who's right?

That's a good question.

Like I stated in my post above, it's really important to make sure you either define them, or reference something like the VIM.

I have sat through many audits where there was 'discussion' regarding what is what. However... there were no findings, because it was defined and consistently applied.

Consistency is the key; which means some training. Training can be touchy on them, because people hold their terms near and dear to their heart. So it's not a right/wrong; tomato/tomatoe things; its just a 'line in the sand' position and you move forward.

 

[John Broomfield]

Adjusting a measuring device so it is calibrated is not repair. It is rework back to the specified requirement. Repair suggests a design change.

Most auto repair shops get this wrong too unless, of course, they are fitting non-OEM parts.

John

 

[Jim Wynne]

Adjusting a measuring device so it is calibrated is not repair. It is rework back to the specified requirement. Repair suggests a design change.

Most auto repair shops get this wrong too unless, of course, they are fitting non-OEM parts.

John

Let me try and shed some light. First, The "re" in "rework" suggests that some type of work has been done that was not, in some way or another, successful. The term definitely doesn't fit here.

As for general terminology:

• People can use whatever words they want to use to describe things so long as everyone who needs to understand the meaning does understand the meaning. The possibility of misunderstanding is reduced by common terminology.
• Move beyond common dictionary denotation with care. If common definitions suffice, leave them alone and resist the temptation to call spades something other than spades. In this case, the common definition of "calibration" is "comparison to a standard." It does not suggest or necessarily entail adjustment. A device that has been compared to a standard and found to be acceptable in accordance with defined criteria, without adjustment, has been calibrated.
• Most calibration processes require more than just comparison. As Hershal pointed out, there are things like uncertainty and traceability to be concerned about. These things apply to the general process and not the act of calibration itself.
• "Verification" is an unnecessarily ambiguous term. Calibration is not necessarily different from verification; calibration is a form of verification. If we have to differentiate between the two, let the definitions be distinct and unambiguous.
• "Validation" happens, in general, to processes and not individual things. Validation is also a form of verification. Validation consists in verifying that given the application of some defined process settings, parameters or requirements, the process output is reasonably predictable.

 

[dgriffith]

I think if we all spoke the language of universal-ese, interpreting terms and definitions would be far less entertaining.

Even though the VIM specifically defines calibration, specifically defines adjustment, and specifically implies that they are not the same thing, other countries' standards writing bodies have modified these definitions to align them with standard practices in their country.
Even at the lowest organizational level, companies can define, as part of their calibration procedure, what calibration means and what decisions and actions can be taken based on the results.

So, calibration can establish the error and assign a value with uncertainties, or it can include decision parameters such as in/out of tolerance, and an action such as adjustment to align the observed value with the standard. This is the common US definition.

 

[BradM]

I think if we all spoke the language of universal-ese, interpreting terms and definitions would be far less entertaining.

Even though the VIM specifically defines calibration, specifically defines adjustment, and specifically implies that they are not the same thing, other countries' standards writing bodies have modified these definitions to align them with standard practices in their country.
Even at the lowest organizational level, companies can define, as part of their calibration procedure, what calibration means and what decisions and actions can be taken based on the results.

So, calibration can establish the error and assign a value with uncertainties, or it can include decision parameters such as in/out of tolerance, and an action such as adjustment to align the observed value with the standard. This is the common US definition.

And.... you're correct too!!

I have been surprised at the different definitions I've run across for calibration:
Measurement without Adjustment; measurement with adjustment; adjustment only; no adjustment; etc. etc.

Second only to the heated debates here about calibrating rulers and tapes, , some of the more spirited (and honestly interesting) discussions have been on what terms mean in this area.

 

[Hershal]

Re: Calibration or Validation?

I was with you until the last sentence. Calibration is comparison to a standard--nothing more. There might be, and ususally, additional requirements for the calibration process, but a device verified against a standard has been calibrated.

Jim,

You may disagree, but both the VIM and NIST Handbook 150 make it clear that uncertainties are a required part of calibration. Therefore, no uncertainty, not calibration.

 

[Hershal]

Re: Calibration or Validation?

I was always under the impression that it is verification until you make an ADJUSTMENT. When you make an adjustment to a standard, then you are calibrating.

No necessarily so. For some calibrations there are incidental adjustments. Normally if an adjustment is required it is not really a calibration. The calibration is subsequent to the adjustment.

 

[Jim Wynne]

Re: Calibration or Validation?

Jim,

You may disagree, but both the VIM and NIST Handbook 150 make it clear that uncertainties are a required part of calibration. Therefore, no uncertainty, not calibration.

Those are standards that have authority only when two or more persons agree to abide by them. Anyone can devise a set of rules for calibration and define terms anyway they see fit. It becomes a standard when another person or entity agrees to its terms. If we are talking strictly about VIM and the NIST handbook, we use the definitions and requirements therein.