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Vernier Calibrations & more


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We recently had an ISO 13485 2016 change audit. The NB auditor pointed out that we should increase the calibration frequency of verniers that we use daily from once in a year to once every quarter . There was no proper justification given . He just stated that for daily use instruments the validation frequency of one year is too long.We have not had any problems with these instruments for last more than three years .

What should we do ? As our cost go very high we have 100 such instruments

Can we do some verification or validation ourselves every quarter and if yes what would be procedure. We are just checking OD . ID and depth with these instruments.

Any help would be highly appreciated.


re: Vernier Calibrations & more

The auditor is using bias to make such comments. What should happen is that the previous calibration data should have been reviewed to determine the condition of the calipers the last time they were calibrated - the 'as found" condition data. You could still do that to disprove the auditor's comment.

In reality, calibrations shouldn't be based on calendar but on use.


Captain Nice
Staff member
re: Vernier Calibrations & more

<snip> He just stated that for daily use instruments the validation frequency of one year is too long. <snip>
Either your auditor or you are probably mixing up terms.

Remember - Validation of a measurement device is not the same as the calibration of a measurement device, and verification of a measurement device is also not the same as either calibration or validation.

Validation - A gage R&R study will tell operators if the measurement system is acceptable for its intended use.

Calibration - See: Verification vs. Validation vs. Calibration - What is the difference? (See Hershal's response in post #4) - "Calibration" is comparison of a measurement device against a known standard and adjustment if necessary.

Verification - Same link as the calibration link above. A check against a reference standard, usually done daily or weekly on daily use instruments, especially those used on critical measurements.

Also see: Calibration vs. Verification of Calibration vs. Verification - Definitions and Calibration vs. Verification - Definition of
You have calibration records on these 100 or so verniers.
Analyze their calibration history - what percentage of these were found to be in tolerance when calibrated?

If you find that say about 95% of them are found in tolerance then you have them at a valid calibration interval, there is no reason to decrease it. In fact, you would have justification to extend the calibration intervals.

On the other hand, if you had less than 85% in tolerance (not a hard and fast number here, just a suggestion) you should be reducing the calibration intervals.

Everything these days is based on a risk assessment. How much would it hurt you if 5%, or 25%, or whatever of your measurements are questionable? How critical are these measurements to your processes? If you calibrate verniers to 0.001" and the measurement they are used on has a 0.01" tolerance there will likely be little risk if a vernier is out of tolerance.


Not out of the crisis
Staff member
Super Moderator
I agree that this is a biased comment.
a "should", if you will.
did he write it as a finding or OFI?

As the others have said - look at the past data. If they are always in spec "As found" then your interval is fine.
If they need frequent recalibration then you should take action.


Wearer of many hats
We have about 50 digital verniers on our system, the majority of which get used multiple times a day. I calibrate mine every six months as I can then detect measurement variation long before it becomes a problem or the gauge fails calibration. They used to be calibrated annually but I found that a gauge could be ok one year and could then fail calibration the next. I have not had this since I have been calibrating them every six months (about 5 years ago).

Agreeing with what has been said previously, my six month calibration cycle is set that way because it works for me and not because an auditor arbitrarily told me to do it that way, in fact I have had quite the opposite experience with auditors asking me why I do it so frequently and not annually like many of the other companies they have visit.
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