Dictionary · 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.
Related terms
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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
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
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
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 Superseded in rigorous work by the test uncertainty ratio, which accounts for the whole measurement process.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
Validation
Verification where the specified requirements are shown to be adequate for an intended use — demonstrating a procedure is fit for its purpose.
VIM (JCGM 200:2012) 2.45
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