The General Conference on Weights and Measures

The General Conference on Weights and measures(French: Conférence Générale des Poids et Mesures, abbreviated CGPM and sometimes referred to as the GCWM) is the international organization made up of the delegates of all member states (47 member states in October 1985). The task of this organization is to take all necessary measures to ensure the propagation and the development of the SI and to adopt various international scientific resolutions relative to new and fundamental developments in metrology.
The International Committee for Weights and measures (CIPM) under the authority of the CGPM is responsible for the establishment and control of units of measurements. The International Bureau of Weights and Measures (BIPM) that was created by the Metric Convention and signed by the 17 nations in Paris in 1875 operates under the supervision of the CIPM. The BIPM, which is located at the Pavillon of Breteuil in the Saint-Cloud Park at Severs is responsible for ensuring unification of measurements throughout the world, especially:

• to establish fundamental standards and scales of the main physical quantities, and to preserve international prototypes,
• to carry out comparisons of national and international standards,
• to ensure co-ordination of appropriate measurement techniques,
• to carry out and co-ordinate the determination of physical constants involved in the above activities.

The major decisions made by CGPM is given in the following table.

CGPM	Date	Decisions
1st CGPM	1889	Sanction of the international prototypes of the metre and the kilogram
3rd CGPM	1901	Declaration concerning the definition of the litre as the volume occupied by 1kg of pure water at the temperature of its maximum desity (abroged in 1964). Declaration of the kilogram as the unit of mass. The weight was defined as the quantity with the dimension of a force. Adoption of the conventional value of standard acceleration due to gravity, i.e., \(g_n = 980.665 \) \(\left[\frac{cm}{s^2}\right]\)
7th CGPM	1927	Definition of the metre by the international Prototype. Definitions of photometric units: the new candle, and new lumen. definitions of mechanical units which enter the definitions of electrical units: joule, watt. definitions of electric units: ampere, volt, ohm, coulomb, farad, henry, and weber (CIPM, 1964).
9th CGPM	1948	Replacement of the melting point of ice by the triple point of water for thermometric reference. Thermodynamic scale with a singe fixed point. Adoption of the joule as unit of qunatity of heat. Adoption of degree Celsius to denote the degree of temperature.
10th CGPM	1954	Definition of the thermodynamic temperature scale by choosing the triple point of water as the fundamental fixed point Definition of the standarad atmosphere:\(101325 \left[\frac{N}{m^2}\right]\). Adoption of six base units of the future SI: metre, kilogram, second, ampere, kelvin, and candela. Definition of the unit of time (CIPM, 1956).
11th CGPM	1960	New definitions of the metre, and of the second. Adoption of the Systeme International d'unites with acronym SI. The litre is exactyl defined as one cubic decimetre (CIPM, 1961).
12th CGPM	1964	Atomic standard of frequency. Standardization of the curie to exactly \(3.7 \times 10^{10} \left[\frac{1}{s}\right]\). Introduction of new SI prefixes femto and atto.
13th CGPM	1967-68	The new definition for the second, the kelvin, and the candela. Abrogation of obsolete units: micron, and new candle. Multiples and submultiples of the unit of mass (CIPM, 1967). Rules of application of the SI (CIPM, 1969).
14th CGPM	1971	Definition of the SI unit of the amount of a substance: mole, and adoption of two new SI derived units: the pascal and the siemens, International atomic time (TAI).
15th CGPM	1975	Recommended values for the velocity of light in vacuum, and new names and units for ionizing radiation qunatities: becqurel; gray, and two new SI prefixes peta and exa. Universal coordinated time (UTC).
16th CGPM	1979	New definition of the candela. Special name for the SI derived unit of the dose equivalent: sievert. The symbol L for litre in addition to the lower case letter l. Introduction of two supplementary units: radian and steradian (CIPM, 1980).
17th CGPM	1983	New definition of the metre as unit of length based on the velocity of light in vacuum. New SI prefixes: zetta, zepto, yotta, and yoct (CIPM,1990).
20th CGPM	1995	Abrogation of the two supplementary units. Hence radian and steradian are now considered as SI derived units with special names.
21st CGPM	1999	Adoption of a new SI derived unit of enzymatic activity: the katal.