Calibration, adjustment and verification are different things
Calibration measures; adjustment changes the instrument; verification compares against a requirement. Mixing them up leads to lost as-found data and unsupported claims.
The international vocabulary is precise. Calibration establishes the relationship between the instrument's indication and the reference value, with uncertainty. Adjustment is the set of operations that change the instrument so that it indicates correctly. Verification is the provision of objective evidence that the instrument meets specified requirements.
Why it matters
- A calibration certificate with no adjustment still carries the full result; the instrument may be used with corrections.
- Adjusting first and calibrating after destroys the as-found evidence about the previous interval.
- A verification ('within tolerance') is only as good as the decision rule and uncertainty behind it.
Ask for calibration data, then decide on adjustment, then re-calibrate if adjusted. Keep all three records.
Frequently asked questions
- Does calibration adjust the instrument?
- No. Calibration only measures. Adjustment is a separate operation that may follow it, and if performed should be followed by a second (as-left) calibration.
- Is a 'calibration check' the same as a calibration?
- Usually it is a verification against a tolerance without a full uncertainty statement. It has value as an intermediate check but does not replace a calibration with reported uncertainty.
References
- [1]JCGM 200:2012 — International vocabulary of metrology (VIM), 3rd edition
- [2]ISO/IEC 17025:2017 — General requirements for the competence of testing and calibration laboratories
General technical guidance written against the cited sources. It is not regulatory or legal advice and does not replace the applicable standard, guideline or a qualified reviewer's judgement.
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