Knowledge
Metrology Dictionary
The complete VIM vocabulary — all numbered concepts of JCGM 200:2012 as faithful paraphrases with clause citations — plus clearly labeled practice terms from the GUM, ILAC, ISO and NIST guidance.
Accreditation
Third-party attestation, by an authoritative body, of a conformity assessment body's competence to carry out specific tasks — for laboratories, against ISO/IEC 17025, by bodies operating under ISO/IEC 17011.
ISO/IEC 17011:2017 · Quality & Accreditation
Calibration and measurement capability (CMC)
The smallest uncertainty of measurement a laboratory can achieve within its accredited scope when performing more or less routine calibrations of nearly ideal devices — the uncertainty published in its scope of accreditation.
ILAC-P14:09/2020 · Quality & Accreditation
Check standard
A stable artifact or instrument measured regularly within a measurement assurance program; its control chart reveals drift, shifts, or loss of statistical control of the process.
NIST SOP 30 / GLP 1 · Quality & Accreditation
Decision rule
A documented rule describing how measurement uncertainty is accounted for when stating conformity with a specified requirement — required by ISO/IEC 17025:2017 when a laboratory reports pass/fail.
ISO/IEC 17025:2017, 3.7 · Quality & Accreditation
Guard band
An interval applied between the tolerance limit and the acceptance limit to control the risk of false accept or false reject given measurement uncertainty — commonly the expanded uncertainty U, per ILAC-G8.
ILAC-G8:09/2019 · Quality & Accreditation
Interlaboratory comparison
Organization, performance, and evaluation of measurements on the same or similar items by two or more laboratories under predetermined conditions.
ISO/IEC 17043:2023 · Quality & Accreditation
Process measurement assurance
A program of intermediate checks using check standards and control charts to demonstrate that a measurement process remains in statistical control between calibrations, as described in NIST SOP 30.
NIST SOP 30 (2019) · Quality & Accreditation
Proficiency testing
Evaluation of participant performance against pre-established criteria by means of interlaboratory comparisons — an ISO/IEC 17025 requirement for demonstrating ongoing competence.
ISO/IEC 17043:2023 · Quality & Accreditation
Test accuracy ratio (TAR)
The legacy ratio of unit-under-test tolerance to the accuracy specification of the standard used. Superseded in rigorous work by the test uncertainty ratio, which accounts for the whole measurement process.
Industry practice · Quality & Accreditation
Test uncertainty ratio (TUR)
The ratio of the tolerance of the unit under test to the expanded uncertainty of the measurement process used to test it. A 4:1 TUR is the traditional benchmark; lower ratios call for guard banding or risk analysis (ANSI/NCSL Z540.3).
ANSI/NCSL Z540.3 · Quality & Accreditation