VIM concept: the anatomy of a traceability chain

'Traceable to NIST' is one of the most-abused phrases in commerce. The VIM's definition (clause 2.41) is stricter and more useful: metrological traceability is the property of a RESULT — not a lab, not an instrument — relating it to a stated reference through a documented, unbroken chain of calibrations, each contributing uncertainty.

Every link must satisfy three tests. There must be a calibration (not merely a purchase or a certificate of conformance); the calibration must state its uncertainty; and the chain must be documented up to the stated reference, normally the SI through a national metrology institute. Break any one — an uncalibrated 'reference' in the middle, a certificate without uncertainty, an undocumented hop — and the property is lost, whatever the paperwork says.

ILAC-P10 lists the acceptable routes for accredited laboratories, and NIST's GMP 13 in the library turns the concept into a checklist a working lab can audit itself against. The dictionary's traceability entries cite the VIM clauses directly.