How to choose a calibration laboratory
Check the accreditation scope for the exact quantity, range and uncertainty you need; then evaluate turnaround, certificate quality and how they handle out-of-tolerance findings.
Six checks
- Accreditation: by a body within the ILAC MRA, for calibration (not only testing).
- Scope: covers temperature (or your quantity) across the range you need, with a CMC at or below the uncertainty you require.
- Method: comparison in bath or dry block; immersion; whether they calibrate loggers as complete systems.
- Certificate content: uncertainty, k, traceability statement, conditions, as-found and as-left values, decision rule.
- Out-of-tolerance handling: do they notify before adjustment? Do they report both states?
- Logistics: turnaround, packaging guidance, whether on-site calibration is offered and how its uncertainty differs.
ValiTrac's laboratory-discovery capability is planned to help match these criteria against published scopes; until then, accreditation-body directories are the authoritative source.
Frequently asked questions
- Is a cheaper non-accredited calibration ever acceptable?
- Only where the result does not need to demonstrate traceability — and under ISO/IEC 17025 or GDP that is rarely the case for measuring equipment that affects results.
References
- [1]ISO/IEC 17025:2017 — General requirements for the competence of testing and calibration laboratories
- [2]ILAC Mutual Recognition Arrangement (ILAC MRA)
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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How to read a scope of accreditation
A scope lists, per quantity, the range, the calibration and measurement capability (CMC) and the method. Reading it tells you whether the laboratory can certify what you need — and at what uncertainty.
What is CMC in calibration?
Calibration and Measurement Capability is a laboratory's best-case uncertainty, not the accuracy of your instrument.