Author(s): K.J. Hume
Metrology is the science of measurements. It may be divided into three levels: 1) Fundamental or scientific metrology, which concerns the establishment of systems of units of measurement, the definition of units, their realisation and the means of dissimination of traceability. Traceability further requires the quantification of uncertainy of measurements, almost a subfield in itself. 2) Applied or industrial metrology, which concerns the use of measurements and measuring instruments for manufacturing, trade, health care, environmental monitoring, etc. 3) Legal metrology, which concerns legislation on allowed units of measurement, requirements for measuring instruments and measurement methods used in society, and quantitative limits for e.g. alchohol in blood, toxic substances in air and water, radiation levels, etc.