Dictionary · Standards & Units
Primary measurement standard
A standard established using a primary reference measurement procedure, or created as an artifact chosen by convention — not calibrated against another standard for the same quantity.
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National measurement standard
A standard recognized by national authority to serve, in a state or economy, as the basis for assigning values to other standards of the same kind.
VIM (JCGM 200:2012) 5.3
Measurement unit
A real scalar quantity, defined and adopted by convention, with which any other quantity of the same kind is compared to express the ratio of the two quantities as a number.
VIM (JCGM 200:2012) 1.9
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
International System of Units (SI)
The system of units based on the ISQ, with unit names, symbols, prefixes, and rules for their use, adopted by the CGPM. Since the 2019 revision all seven base units are defined by fixing the numerical values of seven defining constants.
VIM (JCGM 200:2012) 1.16
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
Reference measurement standard
A standard designated for the calibration of other standards for quantities of a given kind in an organization or at a location — a laboratory's best standard.
VIM (JCGM 200:2012) 5.6