Metrology is the scientific study of measurement. It establishes a common understanding of units, crucial in linking human activities. Modern metrology has its roots in the French Revolution's political motivation to standardise units in France when a length standard taken from a natural source was proposed. This led to the creation of the decimal-based metric system in 1795, establishing a set of standards for other types of measurements. Several other countries adopted the metric system between 1795 and 1875; to ensure conformity between the countries, the Bureau International des Poids et Mesures (BIPM) was established by the Metre Convention. This has evolved into the International System of Units (SI) as a result of a resolution at the 11th General Conference on Weights and Measures (CGPM) in 1960.
A Kibble balance, which is used to measure weight via electric current and voltage. With this instrument, the measurement of mass is no longer dependent on a defined mass standard and is instead dependent on natural physical constants.
Computer-generated image realising the international prototype of the kilogram (IPK), made from an alloy of 90-per cent platinum and 10-per cent iridium by weight
Measurement is the quantification of attributes of an object or event, which can be used to compare with other objects or events.
In other words, measurement is a process of determining how large or small a physical quantity is as compared to a basic reference quantity of the same kind.
The scope and application of measurement are dependent on the context and discipline. In natural sciences and engineering, measurements do not apply to nominal properties of objects or events, which is consistent with the guidelines of the International vocabulary of metrology published by the International Bureau of Weights and Measures. However, in other fields such as statistics as well as the social and behavioural sciences, measurements can have multiple levels, which would include nominal, ordinal, interval and ratio scales.
Four measuring devices having metric calibrations
Detail of a cubit rod in the Museo Egizio of Turin
A baby bottle that measures in three measurement systems—metric, imperial (UK), and US customary.
Measurement station C of EMMA experiment situated at the depth of 75 meters in the Pyhäsalmi Mine.