N.B. This is basically an amalgam of terms in VIM and MINET and other publications from this community (e.g. in the journal Measurement).
- 20091222 - Laurent_Lefort: added references to the sources of the definitions
- 20100112 - Laurent_Lefort: should we consider the definitions from the following refs?
- (MINET)Measuring the Impossible MINET Glossary of Measuring Man
- Rossi: Rossi, G, B (2009): Cross-disciplinary concepts and terms in measurement, Measurement 42(9), November, 2009 and Rossi, G, B (2003) A probabilistic model for measurement processes Measurement 34(2) Septembre 2003
- (ISO 3534) Statistics -- Vocabulary and symbols -- Part 2: Applied statistics ISO 3534-2:2006 1.1.2 (cited by MINET)
- Finkelstein: Finkelstein L 1982 “Theory and philosophy of measurement” in “Handbook of Measurement Science”, Vol. 1, pages 1- 30, J Wiley & Sons. (cited by MINET)
- 20100129 - Laurent_Lefort: Added ref. from VELMEC (not used below)
- VELMEC “[http://www.welmec.org/fileadmin/user_files/publications/8-1.pdfGuide on Terms and definitions in MID and their relation to terms defined in other international metrologically relevant
- 20100709 - Laurent_Lefort:Added Refs found through Singh et al. 2010: Appendix A. Design of ontology on process monitoring and analysis systems - Step 2.2 – Elaborate the important terms The secondary sources are cited when they are available.
- Singh et al. R. Singh, K.V. Gernaey and R.Gani, An ontological knowledge-based system for the selection of process monitoring and analysis tools, Computers & Chemical Engineering, Volume 34, Issue 7, Process Modeling and Control in Drug Development and Manufacturing, 14 July 2010, Pages 1137-1154
- Haby Haby, J. (2008). What is the difference between accuracy and precision? USA: Mississippi State University.
- Carr and Brown Carr, J. J., & Brown, J. M. (2008). Sensor terminology (3rd ed.). National Instruments.
See also more related references in Sensor types
quantity (VIM 1.1): property of a phenomenon, body, or substance, where the property has a magnitude that can be expressed as a number and a reference
NOTE 1 The generic concept ‘quantity’ can be divided into several levels of specific concepts, as shown in the following table (see (VIM) page 16).
Characteristic (ISO 3534), (MINET):distinguishing feature of an item or process ( entity) related to a requirement
Entity (ISO 3534), (MINET): phenomenon, body or material
Quality Finkelstein82, (MINET): abstract, single sensed aspect of object or event (entity) – e.g. ’smell’
kind of quantity (VIM 1.2) : aspect common to mutually comparable quantities (tricky definintion see notes in (VIM) page 17)
quantity value (VIM 1.19), (MINET): number and reference together expressing magnitude of a quantity
quantity-value scale (VIM 1.27): ordered set of quantity values of quantities of a given kind of quantity used in ranking, according to magnitude, quantities of that kind
EXAMPLE 1 Celsius temperature scale.
EXAMPLE 2 Time scale.
EXAMPLE 3 Rockwell C hardness scale.
Measurement (VIM 2.1): process of experimentally obtaining one or more quantity values that can reasonably be attributed to a quantity
Measurement (MINET): Process of associating numbers, in an empirical and objective way, to characteristics of objects and events of the real world in a way so as to describe them
Measurand (VIM 2.3), (MINET): quantity intended to be measured. Note: The specification of a measurand requires knowledge of the kind of quantity, description of the state of the phenomenon, body, or substance carrying the quantity, including any relevant component, and the chemical entities involved.
measurement principle (VIM 2.4), (MINET): phenomenon serving as a basis of a measurement
EXAMPLE 1 Thermoelectric effect applied to the measurement of temperature.
EXAMPLE 2 Energy absorption applied to the measurement of amount-of-substance concentration.
EXAMPLE 3 Lowering of the concentration of glucose in blood in a fasting rabbit applied to the measurement of insulin concentration in a preparation.
NOTE The phenomenon can be of a physical, chemical, or biological nature.
measurement method (VIM 2.5), (MINET): generic description of a logical organization of operations used in a measurement
NOTE Measurement methods may be qualified in various ways such as:
- substitution measurement method,
- differential measurement method, and
- null measurement method;
- direct measurement method, and
- indirect measurement method.
See IEC 60050-300:2001.
measurement procedure (VIM 2.6), (MINET): detailed description of a measurement according to one or more measurement principles and to a given measurement method, based on a measurement model and including any calculation to obtain a measurement result
measurement result (VIM 2.9), (MINET): set of quantity values being attributed to a measurand together with any other available relevant information
- 20091222 - Laurent_Lefort: Note the difference: a result can cover more than one property value
NOTE 2: (VIM), (MINET) A measurement result is generally expressed as a single measured quantity value and a measurement uncertainty. If the measurement uncertainty is considered to be negligible for some purpose, the measurement result may be expressed as a single measured quantity value. In many fields, this is the common way of expressing a measurement result. (VIM)
measurement accuracy (VIM 2.13): closeness of agreement between a measured quantity value and a true quantity value of a measurand
accuracy: Haby “The ability of a measurement to match the actual value of the quantity being measured” (via Singh et al.).
- 20100709 - Laurent_Lefort: the definitions are equivalent - accuracy is more concise
measurement precision (VIM 2.15): closeness of agreement between indications or measured quantity values obtained by replicate measurements on the same or similar objects under specified conditions
precision: Haby The ability of a measurement to be consistently reproduced”, i.e. it is the ability of repeatability (via Singh et al.).
- 20100709 - Laurent_Lefort: the definitions are equivalent - precision is more concise
measurement model (VIM 2.48), (MINET): mathematical relation among all quantities known to be involved in a measurement
NOTE 1 A general form of a measurement model is the equation h(Y, X1, …, Xn) = 0, where Y, the output quantity in the measurement model, is the measurand, the quantity value of which is to be inferred from information about input quantities in the measurement model X1, …, Xn.
NOTE 2 In more complex cases where there are two or more output quantities in a measurement model, the measurement model consists of more than one equation.
measurement function (VIM 2.49): function of quantities, the value of which, when calculated using known quantity values for the input quantities in a measurement model, is a measured quantity value of the output quantity in the measurement model
NOTE 1 If a measurement model h(Y, X1, …, Xn) = 0 can explicitly be written as Y = f (X1, …, Xn), where Y is the output quantity in the measurement model, the function f is the measurement function. More generally, f may symbolize an algorithm, yielding for input quantity values x1, ..., xn, a corresponding unique output quantity value y = f (x1, …, xn).
NOTE 2 A measurement function is also used to calculate the measurement uncertainty associated with the measured quantity value of Y.
influence quantity (VIM 2.52): quantity that, in a direct measurement, does not affect the quantity that is actually measured, but affects the relation between the indication and the measurement result.
measuring instrument (VIM 3.1), (MINET) device used for making measurements, alone or in conjunction with one or more supplementary devices
NOTE 1 A measuring instrument that can be used alone is a measuring system.
NOTE 2 A measuring instrument may be an indicating measuring instrument or a material measure.
measuring system: (VIM 3.2): set of one or more measuring instruments and often other devices, including any reagent and supply, assembled and adapted to give information used to generate measured quantity values within specified intervals for quantities of specified kinds
NOTE A measuring system may consist of only one measuring instrument.
measuring transducer (VIM 3.7): device, used in measurement, that provides an output quantity having a specified relation to the input quantity
EXAMPLES Thermocouple, electric current transformer, strain gauge, pH electrode, Bourdon tube, bimetallic strip.
sensor (VIM 3.8), (MINET): element of a measuring system that is directly affected by a phenomenon, body, or substance carrying a quantity to be measured
EXAMPLES Sensing coil of a platinum resistance thermometer, rotor of a turbine flow meter, Bourdon tube of a pressure gauge, float of a level-measuring instrument, photocell of a spectrometer, thermotropic liquid crystal which changes colour as a function of temperature.
NOTE In some fields, the term “detector” is used for this concept.
detector (VIM 3.9), (MINET): device or substance that indicates the presence of a phenomenon, body, or substance when a threshold value of an associated quantity is exceeded
EXAMPLES Halogen leak detector, litmus paper.
NOTE 1 In some fields, the term “detector” is used for the concept of sensor.
NOTE 2 In chemistry, the term “indicator” is frequently used for this concept.
measuring system: (MINET): empirical system able to interact with the entity to be assessed and to generate, as a result of that interaction, values of the Quality characteristic intended to be assessed.
measuring chain (VIM 3.10): series of elements of a measuring system constituting a single path of the signal from a sensor to an output element
EXAMPLE 1 Electro-acoustic measuring chain comprising a microphone, attenuator, filter, amplifier, and voltmeter.
EXAMPLE 2 Mechanical measuring chain comprising a Bourdon tube, system of levers, two gears, and a mechanical dial.
indication (VIM 4.9), (MINET)</tt: quantity value provided by a measuring instrument or a measuring system
NOTE 1 An indication may be presented in visual or acoustic form or may be transferred to another device. An indication is often given by the position of a pointer on the display for analog outputs, a displayed or printed number for digital outputs, a code pattern for code outputs, or an assigned quantity value for material measures.
NOTE 2 An indication and a corresponding value of the quantity being measured are not necessarily values of quantities of the same kind.
'Observation <tt>(Rossi) The first sub-process of a Measurement process which accounts for transformations in the measuring system giving rise to the observable output (the instrument indication)
Restitution (Rossi) The second sub-process of a Measurement process which includes data processing which yields the final measurement result (the measurement value).
NOTE (Rossi 2003): The observation process is represented as a parametrical probabilistic mapping, from the set of the possible values of the measurand into the set of the observable values. In this way it is possible to represent the effects of both random variations and systematic deviations that may affect the measurement process, within a coherent probabilistic framework. Consequently restitution is viewed as a probabilistic inversion of the mapping describing observation.
measuring interval (VIM 4.7): set of values of quantities of the same kind that can be measured by a given measuring instrument or measuring system with specified instrumental uncertainty, under defined conditions
Operating range (Singh et al.): The operating range of a monitoring tool is defined as the minimum and maximum limiting value that it can measure.
- 20100709 - Laurent_Lefort: shuld not use Operating here because it can be confused with the conditions of use
- 20100709 - Laurent_Lefort: should not use range here because it can be confused with the range of the interval (the difference between the max and min values) rather than the interval itself (which requires two values or more).
steady-state operating condition (VIM 4.8): operating condition of a measuring instrument or measuring system in which the relation established by calibration remains valid even for a measurand varying with time
rated operating condition (VIM 4.9): operating condition that must be fulfilled during measurement in order that a measuring instrument or measuring system perform as designed
NOTE Rated operating conditions generally specify intervals of values for a quantity
limiting operating condition (VIM 4.10): extreme operating condition that a measuring instrument or measuring system is required to withstand without damage, and without degradation of specified metrological properties, when it is subsequently operated under its rated operating conditions
NOTE 1 Limiting conditions for storage, transport or operation can differ.
NOTE 2 Limiting conditions can include limiting values of a quantity being measured and of any influence quantity.
reference operating condition (VIM 4.11): operating condition prescribed for evaluating the performance of a measuring instrument or measuring system or for comparison of measurement results
NOTE 1 Reference operating conditions specify intervals of values of the measurand and of the influence quantities.
NOTE 2 In IEC 60050-300, item 311-06-02, the term “reference condition” refers to an operating condition under which the specified instrumental measurement uncertainty is the smallest possible.
sensitivity of a measuring system (VIM 4.12): quotient of the change in an indication of a measuring system and the corresponding change in a value of a quantity being measured
sensitivity (Singh et al.) : The sensitivity of the sensor is defined as the change in sensor output per unit change in measured quantity.
- 20100709 - Laurent_Lefort: the definitions are equivalent - sensitivity is more concise
selectivity of a measuring system (VIM 4.13): property of a measuring system, used with a specified measurement procedure, whereby it provides measured quantity values for one or more measurands such that the values of each measurand are independent of other measurands or other quantities in the phenomenon, body, or substance being investigated.
resolution (VIM 4.14): smallest change in a quantity being measured that causes a perceptible change in the corresponding indication
NOTE Resolution can depend on, for example, noise (internal or external) or friction. It may also depend on the value of a quantity being measured.
- 20100709 - Laurent_Lefort: the definitions are almost equivalent - although VIM does not talk about the two possibilities (proportion or absolute terms)
resolution (Singh et al.) : The resolution of the sensor is defined as the smallest change in measurable quantity, which the sensor can detect (Sutherland, 2004). In other words, the smallest detectable incremental change of the input variable that can be detected in the output signal. Resolution can be expressed either as a proportion of the reading (or the full-scale reading) or in absolute terms (Carr & Brown, 2008).
- 20100709 - Laurent_Lefort: Let's assume that the difference between the two cases can be sorted out with the help of the quantity / unit of measurement used to express the resolution.
detection limit (VIM 4.18): measured quantity value, obtained by a given measurement procedure, for which the probability of falsely claiming the absence of a component in a material is β, given a probability α of falsely claiming its presence
instrumental drift (VIM 4.21): continuous or incremental change over time in indication, due to changes in metrological properties of a measuring instrument
drift (Singh et al.): Drift is defined as the gradual change in any quantitative characteristic that is supposed to remain constant. It is an undesired change in output over a period of time that is unrelated to the input. It can be due to aging, temperature effects, sensor contamination, etc. (CAPGO, 2007).
- 20100709 - Laurent_Lefort: the definitions are equivalent - drift is more concise
step response time (VIM 4.25): duration between the instant when an input quantity value of a measuring instrument or measuring system is subjected to an abrupt change between two specified constant quantity values and the instant when a corresponding indication settles within specified limits around its final steady value
response time (Singh et al.): The response time can be defined as the time required for a sensor output to change from its previous state to a final settled value (when subjected to a step input change) within a tolerance band of the correct new value
- 20100709 - Laurent_Lefort: the definitions are equivalent - response time is more concise