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.
Accuracy class
A class of instruments or systems that meet stated metrological requirements intended to keep errors or instrumental uncertainties within specified limits under specified conditions — OIML weight classes E1 through M3 are the canonical example.
VIM (JCGM 200:2012) 4.25 · Instruments
Adjustment of a measuring system
The set of operations carried out on a measuring system so that it provides prescribed indications corresponding to given quantity values. Adjustment changes the instrument; calibration afterwards re-establishes its relation to standards.
VIM (JCGM 200:2012) 3.11 · Calibration
Base quantity
A quantity in a conventionally chosen subset of a system of quantities in which no member can be expressed in terms of the others.
VIM (JCGM 200:2012) 1.4 · Standards & Units
Base unit
A measurement unit adopted by convention for a base quantity — in the SI: second, metre, kilogram, ampere, kelvin, mole, candela.
VIM (JCGM 200:2012) 1.10 · Standards & Units
Blank indication
The indication obtained from a phenomenon, body, or substance similar to the one under investigation but for which the quantity of interest is supposed absent or not contributing — the analytical chemist's blank, generalized.
VIM (JCGM 200:2012) 4.2 · Instruments
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
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
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
Expanded measurement uncertainty
The product of a combined standard uncertainty and a coverage factor greater than one: U = k·u꜀. With k = 2 the coverage probability is about 95 % for a normal distribution.
VIM (JCGM 200:2012) 2.35 · Uncertainty
Indicating measuring instrument
A measuring instrument providing an output signal carrying information about the value of the quantity being measured — voltmeters, thermometers, balances.
VIM (JCGM 200:2012) 3.3 · Instruments
Indication
The quantity value provided by a measuring instrument or system — the reading, before any correction.
VIM (JCGM 200:2012) 4.1 · Instruments
Indication interval
The set of quantity values bounded by the extreme possible indications.
VIM (JCGM 200:2012) 4.3 · Instruments
Influence quantity
A quantity that, in a direct measurement, does not affect the quantity actually measured but does affect the relation between the indication and the result — ambient temperature is the classic example.
VIM (JCGM 200:2012) 2.52 · General
Input quantity in a measurement model
A quantity that must be measured, or whose value can be otherwise obtained, to calculate a measured value of the measurand.
VIM (JCGM 200:2012) 2.50 · Uncertainty
Instrument bias
The average of replicate indications minus a reference quantity value — the instrument-level counterpart of measurement bias.
VIM (JCGM 200:2012) 4.20 · Instruments
Instrumental drift
A continuous or incremental change of an indication over time, due neither to a change in the quantity being measured nor to a recognized influence quantity — a key input to calibration-interval decisions.
VIM (JCGM 200:2012) 4.21 · Instruments
Instrumental measurement uncertainty
The component of measurement uncertainty arising from the instrument or system in use, typically obtained from its calibration.
VIM (JCGM 200:2012) 4.24 · Instruments
Intermediate measurement precision
Measurement precision under intermediate precision conditions — the realistic "within-lab, over months" figure that belongs in most uncertainty budgets.
VIM (JCGM 200:2012) 2.23 · Statistics
Intermediate precision condition
A condition set spanning the same procedure and location over an extended period, allowing other factors (operator, reference standard, time) to vary.
VIM (JCGM 200:2012) 2.22 · Statistics
International System of Quantities (ISQ)
The system of quantities based on the seven base quantities: length, mass, time, electric current, thermodynamic temperature, amount of substance, and luminous intensity — the quantity framework beneath the SI.
VIM (JCGM 200:2012) 1.6 · Standards & Units
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 · Standards & Units
International measurement standard
A standard recognized by signatories to an international agreement and intended to serve worldwide.
VIM (JCGM 200:2012) 5.2 · Standards & Units
Intrinsic measurement standard
A standard based on an inherent and reproducible property of a phenomenon or substance — the triple point of water cell, the Josephson voltage standard.
VIM (JCGM 200:2012) 5.10 · Standards & Units
Kind of quantity
The aspect common to mutually comparable quantities — length, mass, and energy are kinds; diameter and wavelength are both quantities of the kind length.
VIM (JCGM 200:2012) 1.2 · Standards & Units
Limiting operating condition
An extreme operating condition an instrument is required to withstand without damage and without degrading specified properties when subsequently operated under rated conditions — survival limits, not working limits.
VIM (JCGM 200:2012) 4.10 · Instruments
Material measure
A device reproducing or supplying, in a permanent manner during its use, quantities of given values — gauge blocks, standard weights, volumetric flasks, standard resistors.
VIM (JCGM 200:2012) 3.6 · Instruments
Maximum permissible error (MPE)
The extreme value of measurement error, with respect to a known reference value, permitted by specifications or regulations for a given instrument. Verification confirms indications fall within ±MPE.
VIM (JCGM 200:2012) 4.26 · Instruments
Measurand
The quantity intended to be measured. Specifying a measurand requires the kind of quantity and a description of the state of the phenomenon, body, or substance carrying it.
VIM (JCGM 200:2012) 2.3 · General
Measured quantity value
The quantity value representing a measurement result — the value actually obtained for the measurand in a given measurement.
VIM (JCGM 200:2012) 2.10 · General
Measurement
The process of experimentally obtaining one or more quantity values that can reasonably be attributed to a quantity, presupposing a description of the quantity, a procedure, and calibrated equipment.
VIM (JCGM 200:2012) 2.1 · General
Measurement accuracy
Closeness of agreement between a measured value and a true value of the measurand. A qualitative concept — a measurement is more accurate when it offers smaller error, but accuracy itself is not a number.
VIM (JCGM 200:2012) 2.13 · General
Measurement bias
The estimate of a systematic measurement error — typically the difference between the mean of repeated indications and an accepted reference value.
VIM (JCGM 200:2012) 2.18 · Statistics
Measurement error
Measured quantity value minus a reference quantity value; comprises a systematic component and a random component.
VIM (JCGM 200:2012) 2.16 · General
Measurement function
The function whose output value, computed from the input quantity values, is the measured value of the output quantity — Y = f(X₁, …, Xₙ) when the model can be solved explicitly.
VIM (JCGM 200:2012) 2.49 · Uncertainty
Measurement method
A generic description of the logical organization of operations used in a measurement — substitution method, differential method, null method.
VIM (JCGM 200:2012) 2.5 · General
Measurement model
The mathematical relation among all quantities known to be involved in a measurement, of the general form f(Y, X₁, …, Xₙ) = 0.
VIM (JCGM 200:2012) 2.48 · Uncertainty
Measurement precision
Closeness of agreement between indications or measured values from replicate measurements under specified conditions — usually expressed as a standard deviation, variance, or coefficient of variation.
VIM (JCGM 200:2012) 2.15 · Statistics
Measurement principle
The phenomenon serving as the basis of a measurement — thermoelectric effect for a thermocouple, Doppler shift for a radar gun.
VIM (JCGM 200:2012) 2.4 · General
Measurement procedure
A detailed description of a measurement according to a principle and method, based on a measurement model — detailed enough that a trained operator can perform it. The SOP is its documented form.
VIM (JCGM 200:2012) 2.6 · General
Measurement repeatability
Measurement precision under repeatability conditions — the tightest, most flattering precision an instrument and operator can show.
VIM (JCGM 200:2012) 2.21 · Statistics
Measurement reproducibility
Measurement precision under reproducibility conditions — what interlaboratory comparisons quantify.
VIM (JCGM 200:2012) 2.25 · Statistics
Measurement result
The set of quantity values attributed to a measurand together with any other available relevant information — generally a measured value with its measurement uncertainty.
VIM (JCGM 200:2012) 2.9 · General
Measurement standard (etalon)
The realization of the definition of a given quantity, with stated value and uncertainty, used as a reference — an artifact, instrument, reference material, or measuring system.
VIM (JCGM 200:2012) 5.1 · Standards & Units
Measurement trueness
Closeness of agreement between the average of infinitely many replicate measured values and a reference value. Trueness relates inversely to systematic error, not random error.
VIM (JCGM 200:2012) 2.14 · Statistics
Measurement uncertainty
A non-negative parameter characterizing the dispersion of the quantity values being attributed to a measurand, based on the information used — the quantitative expression of doubt about a result.
VIM (JCGM 200:2012) 2.26 · Uncertainty
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 · Standards & Units
Measuring chain
The series of elements of a measuring system constituting a single path of the measurement signal from sensor to output element.
VIM (JCGM 200:2012) 3.10 · Instruments
Measuring instrument
A device used for making measurements, alone or in conjunction with supplementary devices.
VIM (JCGM 200:2012) 3.1 · Instruments
Measuring interval
The set of values of quantities of the same kind that can be measured by a given instrument or system with specified instrumental uncertainty under defined conditions — the interval the specifications actually promise.
VIM (JCGM 200:2012) 4.7 · Instruments
Measuring system
One or more measuring instruments and often other devices, assembled and adapted to give measured values within specified intervals for quantities of specified kinds.
VIM (JCGM 200:2012) 3.2 · Instruments
Measuring transducer
A device, used in measurement, that provides an output quantity having a specified relation to the input quantity — a thermocouple, a load cell, a pressure-to-current converter.
VIM (JCGM 200:2012) 3.7 · Instruments
Metrological comparability of measurement results
Comparability of results traceable to the same reference — what shared traceability buys: results that can be meaningfully compared even from different labs and methods.
VIM (JCGM 200:2012) 2.46 · Calibration
Metrological compatibility of measurement results
The property of a set of results for a stated measurand such that the absolute difference of any pair is smaller than a chosen multiple of the standard uncertainty of that difference — the VIM's formal test for "do these results agree".
VIM (JCGM 200:2012) 2.47 · Statistics
Metrological traceability
The property of a result whereby it can be related to a stated reference — usually the SI — through a documented unbroken chain of calibrations, each contributing to the uncertainty.
VIM (JCGM 200:2012) 2.41 · Calibration
Metrological traceability chain
The sequence of standards and calibrations used to relate a result to a stated reference — the concrete path behind a traceability claim.
VIM (JCGM 200:2012) 2.42 · Calibration
Metrological traceability to a measurement unit
Traceability whose stated reference is the definition of a unit through its practical realization — "traceable to the SI" in its precise sense.
VIM (JCGM 200:2012) 2.43 · Calibration
Metrology
The science of measurement and its application — including all theoretical and practical aspects, whatever the uncertainty and field of application.
VIM (JCGM 200:2012) 2.2 · General
Multiple of a unit
A unit obtained by multiplying a given unit by an integer greater than one — the kilometre from the metre.
VIM (JCGM 200:2012) 1.17 · Standards & Units
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 · Standards & Units
Nominal indication interval
The set of values, bounded by rounded or approximate extreme indications, obtainable with a particular setting of the controls and used to designate that setting — the "0–100 V range" on a meter switch.
VIM (JCGM 200:2012) 4.4 · Instruments
Nominal property
A property of a phenomenon, body, or substance that has no magnitude — the sex of a specimen, the color sequence of a resistor, an ISO country code. It can be examined and classified, but not measured.
VIM (JCGM 200:2012) 1.30 · General
Nominal quantity value
A rounded or approximate value of a characterizing quantity of a measuring instrument that guides its appropriate use — the "100 Ω" stamped on a resistor, the "1 kg" of a weight.
VIM (JCGM 200:2012) 4.6 · Instruments
Null measurement uncertainty
The measurement uncertainty when the specified measured value is zero — what limits how confidently a null or tare reading can be trusted.
VIM (JCGM 200:2012) 4.29 · Instruments
Numerical quantity value
The number in a quantity value — the 5.34 in 5.34 m: the ratio of the quantity to its unit.
VIM (JCGM 200:2012) 1.20 · Standards & Units
Numerical value equation
A relation between numerical values that holds only for stated units — the form most spreadsheet formulas quietly are, and the reason unit discipline matters.
VIM (JCGM 200:2012) 1.25 · Standards & Units
Off-system measurement unit
A unit that does not belong to the system of units in use — the day, the electronvolt, and the nautical mile relative to the SI.
VIM (JCGM 200:2012) 1.15 · Standards & Units
Ordinal quantity
A quantity defined by an agreed procedure that can be ranked but has no meaningful algebra — Rockwell hardness or earthquake magnitude: order exists, differences and ratios do not.
VIM (JCGM 200:2012) 1.26 · Standards & Units
Ordinal quantity-value scale
A quantity-value scale for ordinal quantities, established by agreement on a procedure — comparisons of order are valid, arithmetic on the values is not.
VIM (JCGM 200:2012) 1.28 · Standards & Units
Output quantity in a measurement model
The quantity whose measured value is calculated from the input quantity values using the model — the measurand's seat in the mathematics.
VIM (JCGM 200:2012) 2.51 · Uncertainty
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.
VIM (JCGM 200:2012) 5.4 · Standards & Units
Primary reference measurement procedure
A reference procedure used to obtain a result without relation to a standard for a quantity of the same kind — the route by which primary standards are realized.
VIM (JCGM 200:2012) 2.8 · General
Quantity
A property of a phenomenon, body, or substance to which a magnitude can be assigned and expressed as a number and a reference (typically a measurement unit).
VIM (JCGM 200:2012) 1.1 · Standards & Units
Quantity calculus
The set of mathematical rules applied to quantities rather than bare numbers — the algebra by which units propagate through equations.
VIM (JCGM 200:2012) 1.21 · Standards & Units
Quantity dimension
The expression of a quantity's dependence on the base quantities as a product of powers of their dimensions — force has dimension L·M·T⁻².
VIM (JCGM 200:2012) 1.7 · Standards & Units
Quantity equation
A mathematical relation between quantities in a system of quantities, independent of units — v = l/t regardless of whether metres or inches are used.
VIM (JCGM 200:2012) 1.22 · Standards & Units
Quantity of dimension one
A quantity whose dimension has all base-quantity exponents equal to zero — refractive index, strain, a ratio of like quantities; often loosely called "dimensionless".
VIM (JCGM 200:2012) 1.8 · Standards & Units
Quantity value
A number together with a reference (such as a measurement unit) expressing the magnitude of a quantity — 5.34 m, 0.152 kg, or a value on an agreed scale.
VIM (JCGM 200:2012) 1.19 · Standards & Units
Quantity-value scale
The ordered set of values that quantities of a given kind may take — the scale a thermometer or hardness tester reports on.
VIM (JCGM 200:2012) 1.27 · Standards & Units
Random measurement error
The component of measurement error that varies unpredictably in replicate measurements, characterized by a distribution usually summarized by its standard deviation.
VIM (JCGM 200:2012) 2.19 · General
Range of a nominal indication interval
The absolute difference between the extreme values of a nominal indication interval — 200 V for the −100 V to +100 V setting.
VIM (JCGM 200:2012) 4.5 · Instruments
Rated operating condition
An operating condition that must be fulfilled during measurement for an instrument to perform as designed — the environmental and use envelope the specs assume.
VIM (JCGM 200:2012) 4.9 · Instruments
Reference data
Data related to a property of a phenomenon, body, or substance — or to a system of components of known composition or structure — obtained from an identified source, critically evaluated, and verified for accuracy.
VIM (JCGM 200:2012) 5.16 · Standards & Units
Reference material
Material, sufficiently homogeneous and stable with reference to specified properties, established to be fit for its intended use in measurement or in examination of nominal properties.
VIM (JCGM 200:2012) 5.13 · Standards & Units
Reference measurement procedure
A procedure accepted as providing results fit for assessing the trueness of values obtained from other procedures for the same kind of quantity.
VIM (JCGM 200:2012) 2.7 · General
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 · Standards & Units
Reference operating condition
An operating condition prescribed for evaluating the performance of an instrument or for comparing results — the 23 °C ± 1 °C line at the top of a datasheet.
VIM (JCGM 200:2012) 4.11 · Instruments
Reference quantity value
A quantity value used as a basis for comparison with values of quantities of the same kind — a true value, a conventional value, or a standard's certified value, depending on context.
VIM (JCGM 200:2012) 5.18 · Standards & Units
Relative standard measurement uncertainty
A standard uncertainty divided by the absolute value of the measured quantity value — the form specifications and CMCs often quote (parts in 10⁶, percent of reading).
VIM (JCGM 200:2012) 2.32 · Uncertainty
Repeatability condition of measurement
A condition set that includes the same procedure, operators, measuring system, operating conditions, and location, with replicates over a short period.
VIM (JCGM 200:2012) 2.20 · Statistics
Reproducibility condition of measurement
A condition set that includes different locations, operators, and measuring systems applying the same procedure to the same or similar objects.
VIM (JCGM 200:2012) 2.24 · Statistics
Resolution
The smallest change in the quantity being measured that causes a perceptible change in the corresponding indication. Digital resolution contributes a rectangular uncertainty component of (δ/2)/√3.
VIM (JCGM 200:2012) 4.14 · Instruments
Resolution of a displaying device
The smallest difference between displayed indications that can be meaningfully distinguished — for a digital display, one count of the least significant digit.
VIM (JCGM 200:2012) 4.15 · Instruments
Scale of a displaying measuring instrument
The part of a displaying instrument consisting of an ordered set of marks with associated quantity values.
VIM (JCGM 200:2012) 3.5 · Instruments
Secondary measurement standard
A standard established through calibration with respect to a primary standard for a quantity of the same kind.
VIM (JCGM 200:2012) 5.5 · Standards & Units
Selectivity of a measuring system
The property whereby the system provides measured values for one or more measurands that are independent of other measurands or influence quantities.
VIM (JCGM 200:2012) 4.13 · Instruments
Sensitivity of a measuring system
The quotient of the change in an indication and the corresponding change in the value of the quantity being measured.
VIM (JCGM 200:2012) 4.12 · Instruments
Sensor
The element of a measuring system directly affected by the phenomenon, body, or substance carrying the quantity being measured — the Pt resistance element in an SPRT, the seismic mass in an accelerometer.
VIM (JCGM 200:2012) 3.8 · Instruments
Stability of a measuring instrument
The property of an instrument whereby its metrological properties remain constant in time — quantified by the time taken to drift a stated amount, or the change over a stated time.
VIM (JCGM 200:2012) 4.19 · Instruments
Standard measurement uncertainty
Measurement uncertainty expressed as a standard deviation, denoted u — the common currency into which all components are converted before combination.
VIM (JCGM 200:2012) 2.30 · Uncertainty
Standard reference data
Reference data issued by a recognized authority — the CODATA constants and NIST standard reference databases are the working examples.
VIM (JCGM 200:2012) 5.17 · Standards & Units
Steady-state operating condition
An operating condition under which the relation established by calibration remains valid even though the measurand varies with time.
VIM (JCGM 200:2012) 4.8 · Instruments
Step response time
The duration between the instant an input quantity is subjected to an abrupt change between two specified constant values and the instant the indication settles within specified limits of its final steady value.
VIM (JCGM 200:2012) 4.23 · Instruments
Submultiple of a unit
A unit obtained by dividing a given unit by an integer greater than one — the millimetre from the metre.
VIM (JCGM 200:2012) 1.18 · Standards & Units
System of quantities
A set of quantities together with the non-contradictory equations relating them — the framework a system of units is built on.
VIM (JCGM 200:2012) 1.3 · Standards & Units
System of units
A set of base and derived units, with their multiples and submultiples, defined under given rules for a given system of quantities.
VIM (JCGM 200:2012) 1.13 · Standards & Units
Systematic measurement error
The component of measurement error that in replicate measurements remains constant or varies predictably. Known systematic errors are compensated by correction.
VIM (JCGM 200:2012) 2.17 · General
Target measurement uncertainty
An uncertainty specified in advance as an upper limit, decided from the intended use of the result.
VIM (JCGM 200:2012) 2.34 · Uncertainty
Transfer measurement device
A device used as an intermediary to compare measurement standards — transferring, not holding, the quantity value.
VIM (JCGM 200:2012) 5.9 · Standards & Units
Travelling measurement standard
A standard, sometimes of special construction, intended for transport between locations — the artifacts that carry interlaboratory comparisons.
VIM (JCGM 200:2012) 5.8 · Standards & Units
True quantity value
The quantity value consistent with the definition of the quantity. In practice unknowable; measurement estimates it with stated uncertainty.
VIM (JCGM 200:2012) 2.11 · General
Type A evaluation of measurement uncertainty
Evaluation of a component of uncertainty by statistical analysis of measured values obtained under defined conditions — e.g. the standard deviation of the mean of repeated readings.
VIM (JCGM 200:2012) 2.28 · Uncertainty
Type B evaluation of measurement uncertainty
Evaluation of a component of uncertainty by means other than statistical analysis of current measurements — calibration certificates, specifications, handbook data, assumed distributions.
VIM (JCGM 200:2012) 2.29 · Uncertainty
Uncertainty budget
A statement of a measurement uncertainty, its components, and their calculation and combination — usually tabulated with each source, evaluation type, distribution, standard uncertainty, sensitivity coefficient, and contribution.
VIM (JCGM 200:2012) 2.33 · Uncertainty
Unit equation
A mathematical relation between base and derived units — N = kg·m·s⁻².
VIM (JCGM 200:2012) 1.23 · Standards & Units
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 · Quality & Accreditation
Variation due to an influence quantity
The difference in indication, or in the supplied quantity value of a material measure, when an influence quantity assumes two different specified values — the temperature coefficient on a datasheet is one of these.
VIM (JCGM 200:2012) 4.22 · Instruments
Verification
Provision of objective evidence that a given item fulfils specified requirements — e.g. that an instrument performs within its maximum permissible errors. A pass/fail attestation, distinct from calibration.
VIM (JCGM 200:2012) 2.44 · Calibration
Working measurement standard
A standard used routinely to calibrate or verify instruments or systems, itself usually calibrated against a reference standard.
VIM (JCGM 200:2012) 5.7 · Standards & Units
Zero adjustment of a measuring system
Adjustment so that the system provides a null indication corresponding to a zero value of the quantity to be measured.
VIM (JCGM 200:2012) 3.12 · Calibration
Zero error
The datum measurement error when the specified measured value is zero.
VIM (JCGM 200:2012) 4.28 · Instruments