Glossary

• Accuracy: closeness of agreement between a measured quantity value and a true quantity value of a measurand. Not to be confused with precision, which is an indication of the spread of repeated measurements.
• Amplitude: non-negative scalar measure of a wave's magnitude of oscillation i.e., the magnitude of the maximum disturbance in the medium during one wave cycle.
• Artefact: artefacts in signal processing are any perceived distortion or data error caused by the instrument(s) used in the observation
• Bandwidth (of a signal): width of the frequency band outside which the level of any spectral component of a signal does not exceed a specified percentage of a reference level (IEV 161-06-10).
• Bias: a constant offset that exists over the full range of an instrument.
• Black box: a black box is any system in which only the input or output characteristics are of interest i.e., the internal mechanics of the system is of no importance.
• Calibration: operation that, under specified conditions, in a first step, establishes a relation between the quantity values with measurement uncertainties provided by measurement standards and corresponding indications with associated measurement uncertainties and, in a second step, uses this information to establish a relation for obtaining a measurement result from an indication (VIM 2.39).
• First order response: a system characterised by a time constant, that indicates a delay in responding to an instantaneous change in input. First order systems demonstrate a behaviour governed by equations of the following form: y=Ae^(-τ), where τ is called the time constant of the system and is approximately the time it takes for the system to reach an output value of 63 % of its final, equilibrium reading.
• Gauge factor: for a strain gauge, the ratio of relative change in electrical resistance to the mechanical strain.
• Hysteresis: describes the case in which values of the measurand do not produce unique values of the output.
• Impulse response: the time response of a device produced by the application of a Dirac delta-function to the input of the device. The impulse response is the inverse Laplace or Fourier transform of the transfer function. Its convolution with the input function gives the output function (IEV 731-01-55).
• Linearity: extent to which the output of the instrument is linearly proportional to the measurand.
• Primary standard: standard that is designated or widely acknowledged as having the highest metrological qualities and whose value is accepted without reference to other standards of the same quantity (IEV 311-04-02)
• Range: the interval of values between the minimum and maximum values of a quantity that an instrument is designed to measure.
• Resolution: minimum change in measurand that produces a detectable change in output.
• Second order response: in response to a step or impulse input the system behaves as a damped simple harmonic oscillator.
• Sensitivity: how much the output of the instrument changes with a change in the measurand.
• System identification: procedures for creating a mathematical model representing the static and dynamic behaviour of a system (IEV 351-45-07).
• Threshold: minimum level of measurand before output is detectable.
• Traceability (metrological): property of a measurement result whereby the result can be related to a reference through a documented unbroken chain of calibrations, each contributing to the measurement uncertainty (VIM 2.41)
• Zero order response: the output of the system changes instantaneously with changes in the input signal.

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