Key Terms


Metrology is the science of measurments. It includes all theoretical and practical aspects of measurements.



Measurement is a set of operations whose objective is determining the value of a quantity.



Accuracy of measurement is the closeness of the result of a measurement and the true value of the measurand.



Measurand is a particular quantity that is subject to measurement.



Quantity (measurable) is the attribute of a phenomenon, body or substance that may be distinguished qualitatively and determined quantitatively.



Repeatability (of results in measurements) is described as the closeness of the agreement betweenthe results of successive measurements of the same measurand carried out under the same conditions of measurement.



Reproducibility (of results in measurements) is the closeness of the agreement between the results of measurements of the same measurand carried out under changed conditions of measurement.



Uncertainty of measurement is the parameter, associated wiht the result of a measurement, that charcterizes the dispersion of the values that could reasonably be attributed to the measurand.



Measuring Instrument is the device or combination of devices designed for measurement of quantities.



Primary standard is a standard that id designated or widely acknowledged as having the highest metrological qualities and whose value is accepted without reference to other standards of the same quantity.


Secondary standard is a standard whose value is assigned by comparison with a primary standard of the same quantity.



Reference standard is a standard, generally having the highest metrological quality available at a given location or in a given organization, from which measurements made there are derived.



Working standard is a standard that is used routinely to calibrate or check material measures, measuring instruments or reference materials.



Traceability is the property of the result of a measurement or the value of a standard whereby it can be related to stated references, usally national or international standards, through an unbrokern chain of comparisions all having stated uncertainties.



Verification is the confirmation through examination of a given item and provision of objective evidence that it fulfills specified requirements.



Calibration is a set of operations that establish, under specified conditions, the relation betweenthe values shown by a measuring instrument, a measuring system, the values represented by a materialized meaure or by a reference material, and the corresponding values of the quantities established by the standards.