Calibration Due Date - How can I word my procedure?




1) I am have a dissagrement with my boss over my cal due date. My computer software gives a due date as mm/dd/yy, however I would like to state in the procedure that the gauge is not past due until the last day of the month. Everyone outside of my plant says this is how they do it. He insists we would not pass our qs audit with the procedure written this way. He claims that a gauge due on the 1st of the month would still be overdue by 30 days?
2) How can I control or justify changing calibration frequency's ? Is there specific statistical controls or test to do this without great time investments in reserching history files? I am refering now to mechanical gauges(ie. calipers,mic's,etc.)

Leslie Garon


I have answers to your questions. So will others. ;)

As long as your procedure says that the day is unimportant and that calibration is due sometime within the month listed and only considered late when that month is passed (wording better than this is highly recommended ;) LOL) than QS will accept it as long as you do it that way and you can prove it is appropriate.

If your program is set for mm/dd/yy why not try to always use the same /dd/ for all instruments. or see if you can change the format to mm/yy.

This is allowed by QS. Stating that the day listed is a target but it is not considered late until after the last day of the month works.

As for justifying the change, look at your operations:
Is it critical that certian equipment be calibrated on a precision (exact) time schedule or only that the schedule must be accurate (on or about). Is it cost effective? Do you have the resources? Is it efficient? Is there waste as a result? Is the time schedule practical? does it promote quality or make the cost of quality too high? and lastly is it really necessary to calibrate at the frequency currently implemented? For this last question, use history data and mfg'r recommendation as a guide.

I hope this was some help.

Don Winton


I agree with Leslie. I would suggest the mm/yy (or yy/mm) format. As far as justifying the changes, I am sure your document control procedure allows for this kind of flexibility. You are not changing the frequency, just the details. The yy/mm format that I used in a MIL-I-45208 environment was fine with the GSA auditors (surely QS assessors are not as bad as the GSA guys). I would drop the /dd/ from the date format, audit your documentation to ensure that it is up to date, and carry on.

I am not a QS specialist, but I know that this method would work for an ISO style of assessment. Justify and document; you should be fine.

Best Regards,


1) We state in our procedure that the calibration is due sometime during the month noted as the due "date". So far, it has passed 2 surveillance audits and 3 different auditors with no problems.
2)As far as changing the calibration frequency, we base it on historical data (we have checked this gage once a month and have never found a problem - we can change it to every 6 months.) We do not mess with frequencies on items that measure critical parameters in our system (such as chemistries and temperatures).
I hope this helps.

Scott Knutson

Scott -
We do the same thing as Jennifer's company, including using historical data to change cal frequencies, and we are QS certified.


Fully vaccinated are you?
I know we had a calibration frequency debate going in a recent thread, but the search engine didn't find it - so I'm putting this here. If anyone knows where the other cal frequency thread is, let me know and I'll link these.


Date: Thu, 9 Sep 1999 10:33:25 -0700
From: Bruce Mayfield
To: Greg Gogates
Subject: Survey Results

To learn more about how other companies, organizations and our customers handled calibration intervals I set up a Focus group to discuss two questions

These were:

1. Does your company use the recommended interval on the Calibration Certificate to determine your calibration interval?

2. Does this change cause you any problem with your subcontractors not providing a recommended calibration interval in compliance to the requirement?

Here are the results I obtained through the sample of respondents I received:

Demographically here is how the group broke down:

Government Internal Service Company
Labs Company Labs Testing/ Calibration Labs

13.7% 48.3% 37.9%

The focus group contained organizations from the USA and other countries:

USA Other

78.6% 21.4%

Question #1. 27.5% responded Yes they used the recommended intervals.
They also stated that they used them (about 50% of the
respondents) as the introductory interval and then adjusted
the interval to meet their internal requirements. About 50%
of those responding Yes, represented facilities out side of
the USA. The balance, 72.4%, developed their own
internal calibration intervals and did not use the
recommended intervals from other companies/organizations.

Question #2. 17.2% responded Yes that it would cause a problem. In
reviewing the respondents 50% (8.5%) of those identifying
Yes were out side of the USA. About 50% represented the
USA. Again the balance of the respondents 82.7% stated
that it would not make any difference at all.

In summary, if I take all of the comments and numbers as a whole, in only a minority of cases do individual organizations need or use externally derived recommended intervals. Most of those that do, use them as a starting basis for determining their internal derived interval. Those that do use recommended intervals, have not developed the means to properly determine intervals. Those individuals responding from countries that are not as industrialized as the USA, I can understand why there would be problems with this concept. For those organizations in the USA deriving intervals solely based on someone's else's concept of intervals are not in step with concepts outlined in the various guides and standards.

I also want to thank all of those who responded and to Greg Gogates for his patience in forwarding many of the e-mails over to me.

Bruce Mayfield


Frequency of Gage R&R


I am rather new to the area of Gage R&R, Does QS9000 via MSA set a guideline on how often something needs to have Gage R&R studies done? I have read through each....maybe I missed it...

Or is this based on usage or %R&R values

Thanks for your help!


I am not aware of QS requiring specific calibration period.
It is your decision based on how often you use the gauge, how critical is the feature measured.....
What could help as well would to do a wear sudy on the gauges based on at least 3 previous calibration results.My company has just been certified to the TS16949 standard, and the auditor was quite picky on the MSA studies, how they are performed and why.
Hoping this will help a bit, good luck!!!
Audrey :) :)


This helps......however our gauges dont consist of parts but rather titration test, analytical testing....

I dont know if that matters....thanks for your help!

I love this Forum:cool:

Atul Khandekar

Calib freq

Is it possible / acceptable (to auditors) to perform condition based calibration rather than having a fixed frequency ?

I think the Stability test in MSA may be a good method to determine if the instrument is deteriorating and needs calibration.

- Atul.
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