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.
Calibration
The operation that, under specified conditions, first establishes a relation between values (with uncertainties) provided by measurement standards and corresponding indications (with uncertainties), and second uses that information to obtain results from indications. Calibration is not adjustment.
VIM (JCGM 200:2012) 2.39 · Calibration
Calibration curve
The expression of the relation between indication and corresponding measured quantity value established by calibration — the diagram's central line, without the uncertainty strip.
VIM (JCGM 200:2012) 4.31 · Calibration
Calibration diagram
A graphical expression of the relation between indication and corresponding measurement result, showing the strip of estimated uncertainty around the relation.
VIM (JCGM 200:2012) 4.30 · Calibration
Calibration hierarchy
The sequence of calibrations from a stated reference to the final measuring system, each calibration depending on the previous one; uncertainty necessarily grows down the chain.
VIM (JCGM 200:2012) 2.40 · Calibration
Calibrator
A measurement standard used in calibration — in some fields, a device or material whose assigned value is transferred to the instrument under calibration.
VIM (JCGM 200:2012) 5.12 · Calibration
Certified reference material (CRM)
A reference material accompanied by documentation issued by an authoritative body providing property values with uncertainties and traceability using valid procedures — per ISO 17034 practice.
VIM (JCGM 200:2012) 5.14 · Standards & Units
Coherent derived unit
A derived unit that is a product of powers of base units with no numerical factor other than one — the newton is coherent in the SI; the kilometre per hour is not.
VIM (JCGM 200:2012) 1.12 · Standards & Units
Coherent system of units
A system of units in which every derived unit is coherent — the SI as used with its base and coherent derived units.
VIM (JCGM 200:2012) 1.14 · Standards & Units
Combined standard measurement uncertainty
The standard uncertainty obtained from the individual standard uncertainties (and covariances) of the input quantities through the measurement model — root-sum-of-squares in the uncorrelated case, denoted u꜀.
VIM (JCGM 200:2012) 2.31 · Uncertainty
Commutability of a reference material
The property demonstrated by the closeness of agreement between the relation among results for a stated quantity in the RM and the relation among results for representative routine samples, across specified procedures — whether the RM behaves like the real thing.
VIM (JCGM 200:2012) 5.15 · Standards & Units
Conservation of a measurement standard
The set of operations necessary to preserve the metrological properties of a standard within stated limits — storage, handling, surveillance, and use discipline.
VIM (JCGM 200:2012) 5.11 · Standards & Units
Conventional quantity value
A quantity value attributed to a quantity by agreement for a given purpose — the conventional value of local gravity, or the conventional mass of a weight.
VIM (JCGM 200:2012) 2.12 · General
Conventional reference scale
A quantity-value scale defined by formal agreement — pH and the practical temperature scales are canonical examples.
VIM (JCGM 200:2012) 1.29 · Standards & Units
Conversion factor between units
The ratio of two units for quantities of the same kind — 25.4 mm/in; the numerical value changes, the quantity does not.
VIM (JCGM 200:2012) 1.24 · Standards & Units
Correction
Compensation for an estimated systematic effect, applied additively or multiplicatively. The uncertainty of the correction itself must enter the budget.
VIM (JCGM 200:2012) 2.53 · General
Coverage factor
The number k by which a combined standard uncertainty is multiplied to obtain an expanded uncertainty; k = 2 is standard certificate practice, with a t-based k when effective degrees of freedom are small.
VIM (JCGM 200:2012) 2.38 · Uncertainty
Coverage interval
The interval containing the set of true quantity values of a measurand with a stated probability, based on available information — unlike a classical confidence interval, not necessarily centred on the measured value.
VIM (JCGM 200:2012) 2.36 · Uncertainty
Coverage probability
The probability that the set of true quantity values of a measurand is contained within a specified coverage interval — commonly 95 % in calibration practice.
VIM (JCGM 200:2012) 2.37 · Uncertainty