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.
Datum measurement error
The measurement error of an instrument or system at a specified measured value — the error quoted at a named point rather than over the whole interval.
VIM (JCGM 200:2012) 4.27 · Instruments
Dead band
The maximum interval through which the value of the quantity being measured can be changed in both directions without producing a detectable change in indication — hysteresis's operational signature.
VIM (JCGM 200:2012) 4.17 · Instruments
Deadweight tester
A pressure standard in which known masses acting on a piston of known effective area generate reference pressures — the primary realization of pressure in many calibration laboratories.
Pressure metrology practice · Pressure
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
Definitional uncertainty
The component of uncertainty resulting from the finite detail in the definition of the measurand itself — the floor below which no better procedure can go without redefining the quantity.
VIM (JCGM 200:2012) 2.27 · Uncertainty
Derived quantity
A quantity in a system of quantities defined in terms of the base quantities of that system — speed, force, pressure.
VIM (JCGM 200:2012) 1.5 · Standards & Units
Derived unit
A measurement unit for a derived quantity, formed as a product of powers of base units — the newton (kg·m·s⁻²) or the pascal (N/m²).
VIM (JCGM 200:2012) 1.11 · Standards & Units
Detection limit
The measured value, obtained by a given procedure, for which the probability of falsely claiming absence of a component is β, given a probability α of falsely claiming its presence — the statistically honest "smallest amount we can claim to see".
VIM (JCGM 200:2012) 4.18 · Instruments
Detector
A device or substance that indicates the presence of a phenomenon, body, or substance when a threshold of an associated quantity is exceeded — presence, not magnitude.
VIM (JCGM 200:2012) 3.9 · Instruments
Discrimination threshold
The largest change in the value of the quantity being measured that causes no detectable change in the corresponding indication — stickiness quantified.
VIM (JCGM 200:2012) 4.16 · Instruments
Displaying measuring instrument
An indicating instrument whose output signal is presented in visual form.
VIM (JCGM 200:2012) 3.4 · Instruments