Many people think when you send you meter in for "calibration" that they actually adjust it to be spot on, this is untrue, they just check it and give you a report on the values and whether it's within spec or not.
That's exactly how it is.
This is how an accredited (listed) calibration laboratory does it.
Either it passes or it is blocked with a query as to whether it should be adjusted or not.
As a rule, the devices are then sent to the manufacturer, and after re-adjustment they are sent back to the calibration laboratory.
However:
You have to specifically ask for a "calibration adjustment" if you want this.
And "adjustment" is not something that is normally done in any environment that takes calibration seriously. Why? Because you have just reset all of your tracable history and hence "measurement confidence" of this meter.
It sounds silly, as you just adjusted it to "spot on", but if you understand what tracable calibration is this is something you usually don't want. The tracabe history is usually more important than the absolute value.
Spot on again.
This is a popular question from auditors to us (me as the person responsible for the test field and to my measuring equipment representative, who is in charge of calibration and maintains the database of our test equipment):
Regular traceable calibration is all well and good, but what do you then do with the logs and, above all, with the results from them?
Do you simply file them away and only react when a calibration has failed?
What does your reaction look like then?
I can say that if a calibration fails, that would be FATAL.
And that's what the auditor is getting at.
If a measuring device passed calibration last year and now it hasn't, that doesn't mean it's OK, so we have it checked by the manufacturer and then calibrated again.
That means :
- What was measured with the device in the last 12 months after the last calibration, which products.
- Since nobody can say whether the device went out of tolerance after day 1 after calibration or only on day 364 before the next calibration, everything that was measured with it must be questioned.
- Are the products measured with it still in the company? You were lucky.
But rather not, they have already been delivered, then recall actions must be started, with the corresponding consequences such as economic and of course “loss of face”.
This must be prevented at all costs.
Therefore, the task is not only to manage the calibration results but also to check exactly where the trend of the measured values is heading.
In order to be able to intervene in good time if the trend turns negative.