Check calibration evidence against the measurement you use

A calibration certificate should be checked against the measurement the instrument actually performs. Confirm the instrument identity, relevant range, reported results and uncertainty, then have a competent person decide whether the equipment is suitable for its intended use. Filing a certificate or attaching a new sticker does not complete that decision.

This guide is for Singapore operations teams purchasing calibration services, including teams sharing equipment across regional sites. Global ACI has taken over the former IAF and ILAC roles. Its current catalogue continues to list ILAC P10:07/2020 for metrological traceability, while Global ACI-TECH-1-009 (M), implemented on 26 June 2026, carries the calibration-uncertainty policy formerly published as ILAC P14:09/2020 without substantive changes. These are accreditation policies, not universal acceptance tolerances for every instrument. Current calibration-uncertainty policy Global ACI document continuity The earlier ILAC policy documents remain available as legacy references.

Define the measurement requirement before ordering calibration. Match the certificate to the physical instrument and the laboratory's relevant scope. Keep calibration results separate from the organisation's decision to use the instrument. Investigate the implications of unacceptable results rather than merely shortening the next calibration interval.

Record what is measured, the operating range, conditions and decision made from the reading. A device used for a broad process indication may have a different suitability requirement from one used to accept a product. Ask the responsible technical owner to establish the tolerance and uncertainty needs; do not let a purchasing template choose them accidentally.

Identify accessories or software that influence the result. Where a probe and display are used as a pair, check whether the calibration covers that configuration. Confirm the required measurement points with the laboratory before dispatch, especially if only part of the instrument's range is used.

Compare the serial number, asset number and description with the equipment received. Check calibration date, method, units, measurement points and any stated limitations. Review whether adjustments occurred and whether results before and after adjustment are available when needed for the use decision.

For a claimed accredited calibration, verify the provider and relevant scope through the appropriate accreditation body's directory. A general accreditation claim is not evidence that every service or measurement range is covered. ILAC P10 sets out accepted traceability routes in its policy context; the competent reviewer should assess the route applicable to the measurement. ILAC metrological traceability policy

Ask the technical reviewer to document the acceptance basis, including uncertainty where it affects the decision. Do not invent a universal ratio between tolerance and uncertainty. If a certificate includes a conformity statement, understand the decision rule and the requirement against which the statement was made.

Where results are unsuitable or unclear, keep the instrument out of the affected use until resolved. Determine which earlier measurements may have depended on it. The investigation should consider the last known acceptable condition, intervening checks and actual use; a failed result today does not establish exactly when performance changed.

Assume an invented Singapore warehouse uses a probe for an internal process check around 5 degrees Celsius. The returned certificate contains only measurements at 25 and 50 degrees. The example does not establish a regulated storage requirement or a suitable calibration method.

The coordinator checks that the serial number matches, but does not approve return to use merely because the certificate is genuine. The technical owner asks whether the reported range supports the intended task and requests suitable evidence from the provider. Until that decision is resolved, an already approved alternative instrument is used for the affected check.

If later evidence reveals that previous readings were unreliable, the response includes an impact assessment of the relevant decisions. Replacing the certificate alone would not address potentially affected work. Our guide to evidence of corrective action effectiveness helps separate the administrative correction from proof that the underlying issue has been resolved.

Fictional screening example. A technical owner defines an internal maximum absolute error of 0.50 °C at the relevant operating point. The certificate reports an indication error of +0.30 °C and expanded uncertainty of 0.25 °C, on its stated coverage basis. Assume the reading is used without applying a correction.

For this illustration only, the owner has selected a conservative rule: accept this point only when absolute error + expanded uncertainty ≤ 0.50 °C. The calculation is 0.30 + 0.25 = 0.55 °C, so the point does not meet that chosen rule even though the reported error alone is smaller than 0.50 °C.

If the same reported error had uncertainty of 0.15 °C, the result would be 0.30 + 0.15 = 0.45 °C, meeting that rule at that point. This changes the screening result; it does not establish fitness at other temperatures, under different operating conditions or after subsequent drift.

The arithmetic is deliberately simple. This is not an ILAC-prescribed universal rule and is not a complete uncertainty budget for operational use. The competent owner must select and document the actual decision rule, account for the measurement method and other relevant contributions, and consider whether corrections are applied. Record the instrument's approved range and restrictions rather than converting one acceptable point into unrestricted approval.

Record the certificate reference, approved use, restrictions, reviewer, decision date and next review trigger. Preserve the original certificate and any clarification correspondence. If equipment moves to another site or is used for a new range, reassess suitability rather than carrying forward an unrestricted approval.

Choose review and calibration arrangements from technical needs, operating experience and applicable requirements. This article does not prescribe a fixed annual interval. Protect certificate integrity, and make the approved status easy for the person selecting equipment to see.

It provides measurement evidence. Suitability also depends on the intended use, acceptance criteria, configuration and relevant limitations.

Only through a clear agreed basis where appropriate. The organisation needs to understand and authorise the requirement governing its own measurement decision.

Ask the laboratory or accreditation body for clarification and record the answer. Hold claims about accredited scope that cannot be substantiated.

ILAC policy documents — Legacy catalogue lists P10:07/2020 and P14:09/2020. For the current uncertainty-policy reference, use Global ACI-TECH-1-009 (M) linked above; no universal equipment tolerance is prescribed.

ILAC metrological traceability policy — P10:07/2020, still listed in Global ACI’s current legacy-document catalogue. Read with the applicable accreditation scope.

QSE Advisory is part of the QSE Advisory brand family. Preparation included AI-assisted research and drafting. Examples are hypothetical.

This article is general information. Verify current requirements and seek qualified advice for your specific circumstances.

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