Reading and using calibration certificates
What every line on an accredited certificate means, how to judge whether an instrument is fit for use, and how to catch a weak certificate before it reaches your records.
9 articles · about 28 min · for Anyone who receives calibration certificates: quality, metrology, maintenance and purchasing.
- 01CalibrationWhat should a calibration certificate contain?A checklist for reading a certificate — and the items whose absence should make you ask questions.3 min
- 02CalibrationWhat is CMC in calibration?Calibration and Measurement Capability is a laboratory's best-case uncertainty, not the accuracy of your instrument.3 min
- 03CalibrationCalibration, adjustment and verification are different thingsCalibration measures, adjustment changes the instrument, verification compares against a requirement. Mixing them up loses the as-found data for good.3 min
- 04CalibrationAs-found vs as-leftWhy both sets of readings matter, and what to do when the as-found data are out of tolerance.3 min
- 05CalibrationTolerance versus uncertaintyTolerance is what you require of the instrument; uncertainty is how well the calibration could measure it. A conformity statement needs both.3 min
- 06UncertaintyWhat is a decision rule and why every certificate needs oneA decision rule states how measurement uncertainty is accounted for in declaring pass or fail: simple acceptance, guard banding or a non-binary statement.3 min
- 07UncertaintyGuard banding explained with a worked exampleA guard band narrows the acceptance zone by a multiple of the uncertainty so that a 'pass' has a controlled probability of being wrong. Here is the arithmetic.4 min
- 08CalibrationHow to set calibration intervalsThere is no universal interval. Set it from risk, manufacturer data and — above all — the instrument's own as-found history.3 min
- 09Laboratory DiscoveryCalibration certificate red flagsNo uncertainty, no k, no traceability statement, a 'pass' with no decision rule, or a missing accreditation symbol — each is a reason to query it.3 min
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