General Conference on Weights and Measures

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General Conference on Weights and Measures

The General Conference on Weights and Measures is the English name of the Conférence générale des poids et mesures (CGPM, never GCWM). It is one of the three organizations established to maintain the International System of Units (SI

Si, si, or SI may refer to :...
) under the terms of the Convention du Mètre (Metre Convention) of 1875. It meets in Sèvres

Sèvres

S?vres is a Communes of France in the southwestern suburbs of Paris, France. It is located 9.9 km from the Kilometre Zero.The town is known for its porcelain manufacture, the Manufacture nationale de S?vres, making the famous S?vres porcelain, as well as being the location of the International Bureau of Weights and Measures,...
(in the southwestern suburbs of Paris

Paris

Paris is the Capital of France and the country's largest city. It is situated on the river Seine, in northern France, at the heart of the ?le-de-France Regions of France ....
) every four to six years.

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Si, si, or SI may refer to :...
) under the terms of the Convention du Mètre (Metre Convention) of 1875. It meets in Sèvres

Sèvres

Paris

CGPM Meetings

(1889)	kilogram Kilogram The kilogram or kilogrammeThe spelling kilogram is used by the International Committee for Weights and Measures and the U.S.... defined as mass of the international prototype kilogram (IPK) made of platinum Platinum Platinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River." It is in Group 10 of the periodic table of elements.... -iridium Iridium Iridium is the chemical element with atomic number 77, and is represented by the symbol Ir. A very hard, brittle, silvery-white transition metal of the platinum group, iridium is the second densest element and is the most corrosion-resistant metal, even at temperatures as high as 2000 ?C.... and kept at the International Bureau of Weights and Measures International Bureau of Weights and Measures File:Metric seal.svgThe International Bureau of Weights and Measures , is an international standards organization, one of three such organizations established to maintain the International System of Units under the terms of the Metre Convention .... (Bureau international des poids et mesures), Sèvres Sèvres S?vres is a Communes of France in the southwestern suburbs of Paris, France. It is located 9.9 km from the Kilometre Zero.The town is known for its porcelain manufacture, the Manufacture nationale de S?vres, making the famous S?vres porcelain, as well as being the location of the International Bureau of Weights and Measures,... , France. International prototype metre sanctioned.
(1897)	No resolutions were passed by the 2nd CGPM.
(1901)	litre Litre The litre or liter is a unit of volume. There are two official symbols: the Latin letter L in lower and upper case . The lower case L is often written as a cursive l to avoid confusion with the number 1 in antiqua fonts.... redefined as volume of 1 kg of water. Clarified that kilograms are units of mass, "standard weight" defined, standard acceleration of gravity Standard gravity Standard gravity, usually denoted by g0 or gn, is the nominal acceleration due to Earth's gravity at the Earth's surface at sea level.... defined endorsing use of grams force and making them well-defined.
(1907)	carat Carat (mass) The carat is a unit of mass used for measuring gemstones and pearls . Currently a carat is defined as exactly 200 milligram . This definition, known as the metric carat, was adopted in 1907 at the Fourth General Conference on Weights and Measures, and soon afterwards in many countries around the world.... = 200 mg adopted.
(1913)	International Temperature Scale proposed.
(1921)	Metre Convention revised.
(1927)	Consultative Committee for Electricity (CCE) created.
(1933)	Need for absolute electrical unit identified.
(1948)	ampere Ampere The ampere is the International System of Units unit of electric current. The ampere, in practice often shortened to amp, is an SI base unit, and is named after Andr?-Marie Amp?re, one of the main discoverers of electromagnetism.... , bar Bar (unit) The bar , decibar and the millibar are units of pressure. They are not SI units, nor are they cgs units, but they are accepted for use with the SI.... , coulomb Coulomb The coulomb is the SI unit of electric charge. It is named after Charles-Augustin de Coulomb.... , farad Farad The farad is the SI unit of capacitance. The farad is named after the British physicist Michael Faraday.... , henry, joule Joule The joule is the SI derived unit of energy in the International System of Units. It is defined as:One joule is the amount of energy required to perform the following actions:... , newton Newton The newton is the International System of Units SI derived unit of force, named after Isaac Newton in recognition of his work on classical mechanics.... , ohm, volt Volt The volt is the SI SI derived unit of electric potential difference or electromotive force, commonly known as voltage. It is named in honor of the Lombard physicist Alessandro Volta , who invented the voltaic pile, possibly the first chemical battery .... , watt WATT WATT is a radio station broadcasting a News radio-Talk radio-Sports radio format. Licensed to Cadillac, Michigan, it first began broadcasting in 1945.... , weber Weber (unit) In physics, the weber is the SI physical unit of magnetic flux. It is named after the Germany physicist Wilhelm Eduard Weber .... defined. Chose degree Celsius Celsius Celsius is a temperature scale that is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death.... from among the three names then in use. l (lowercase L) adopted as symbol for litre. Both the comma and dot on a line are accepted as decimal marker symbols. Symbols for the stere Stère The st?re is a measurement unit for volume of wood and equals one cubic metre.The name originally comes from the Greek stereos, meaning solid.... and second Second The second , sometimes abbreviated sec., is the name of a units of measurement of time, and is the International System of Units SI base unit of time.... changed . The universal return to the Long Scale Long and short scales The long and short scales are two different numerical systems used throughout the world:Note that the difference between the two scales grows as numbers get larger.... numbering system was proposed but not adopted.
(1954)	kelvin Kelvin The kelvin is a Units of measurement of temperature and is one of the seven SI base units. The Kelvin scale is a Thermodynamic temperature scale where absolute zero, the theoretical absence of all thermal energy, is zero .... , standard atmosphere Standard atmosphere Standard atmosphere can refer to:* A standard reference value for air pressure: Atmosphere , an approximation of the value at sea level Atmospheric pressure#Standard atmospheric pressure, other reference values... defined. International System of Units (metre Metre The metre or meter is a Unit of measurement of length. It is the SI base unit of length in the metric system and in the International System of Units , used around the world for general and scientific purposes.... , kilogram Kilogram The kilogram or kilogrammeThe spelling kilogram is used by the International Committee for Weights and Measures and the U.S.... , second Second The second , sometimes abbreviated sec., is the name of a units of measurement of time, and is the International System of Units SI base unit of time.... , ampere Ampere The ampere is the International System of Units unit of electric current. The ampere, in practice often shortened to amp, is an SI base unit, and is named after Andr?-Marie Amp?re, one of the main discoverers of electromagnetism.... , kelvin Kelvin The kelvin is a Units of measurement of temperature and is one of the seven SI base units. The Kelvin scale is a Thermodynamic temperature scale where absolute zero, the theoretical absence of all thermal energy, is zero .... , candela Candela The candela is the SI base unit of luminous intensity; that is, power emitted by a light source in a particular direction, weighted by the luminosity function .... ) began.
(1960)	metre redefined in terms of wavelengths of light. Units: hertz Hertz The hertz is a measure of frequency per unit of time, or the number of list of cycles per second. It is the SI base unit of frequency in the International System of Units , and is used worldwide in both general-purpose and scientific contexts.... , lumen Lumen (unit) The lumen is the SI unit of luminous flux, a measure of the perceived power of light. Luminous flux differs from radiant flux, the measure of the total power of light emitted, in that luminous flux is adjusted to reflect the varying sensitivity of the human eye to different wavelengths of light.... , lux Lux The lux is the SI unit of illuminance and luminous emittance. It is used in photometry as a measure of the apparent intensity of light hitting or passing through a surface.... , tesla Tesla (unit) The tesla is the SI derived unit of magnetic flux density B . The tesla is equal to one weber per square metre and was defined in 1960 in honor of inventor, scientist and electrical engineer Nikola Tesla.... adopted. New metric system given the official symbol SI for *Système International d'Unités, the "modernized metric system". Prefixes pico-, nano-, micro-, mega-, giga-* and tera- confirmed.
(1964)	original definition of litre Litre The litre or liter is a unit of volume. There are two official symbols: the Latin letter L in lower and upper case . The lower case L is often written as a cursive l to avoid confusion with the number 1 in antiqua fonts.... = 1 dm³ restored. atto- and femto- prefixes.
(1967)	second redefined as duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium Caesium Caesium or cesium is the chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of , which makes it one of only liquid metal that are liquid at or near room temperature.... -133 atom at a temperature of 0 K. Degree Kelvin renamed kelvin. Candela redefined.
(1971)	new SI base unit SI base unit The International System of Units defines seven dimensional analysis SI base units. All other physical units can be derived from these base units: these are known as SI derived units.... mole Mole (unit) The mole is a Units of measurement of amount of substance: it is an SI base unit, and one of the few units used to measure this physical quantity.... defined. pascal Pascal (unit) The pascal is the SI derived unit of pressure, stress , Young's modulus and tensile strength. It is a measure of force per unit area i.e. equivalent to one newton per square meter or one joule per cubic meter.... , siemens Siemens (unit) The siemens is the SI SI derived unit of electric conductance. It is equal to inverse ohm. It is named after the Germany inventor and industrialist Ernst Werner von Siemens, and was previously called the #Mho.... approved.
(1975)	peta- and exa- prefixes. gray Gray (unit) The gray is the SI unit of absorbed dose due to ionizing radiation .... and becquerel Becquerel The becquerel is the SI derived unit of Radioactive decay. 1 Bq is defined as the activity of a quantity of radioactive material in which one atomic nucleus decays per second.... radiological units.
(1979)	candela Candela The candela is the SI base unit of luminous intensity; that is, power emitted by a light source in a particular direction, weighted by the luminosity function .... , sievert Sievert The sievert is the SI derived unit of equivalent dose. It attempts to reflect the biological effects of radiation as opposed to the physical aspects, which are characterised by the absorbed dose, measured in Gray .... defined. Both l and L provisionally allowed as symbols for litre.
(1983)	metre redefined in terms of the speed of light, but keeps same length.
(1987)	conventional values adopted for Josephson constant, K_J, and von Klitzing constant, R_K, preparing the way for alternative definitions of the ampere and kilogram.
(1991)	new prefixes yocto-, zepto-, zetta- and yotta-.
(1995)	SI supplementary unit SI supplementary unit Until 1995, SI supplementary units were:As of October 1995, the category of "supplementary units" has been abolished from the SI system of measurement, and the radian and the steradian are now considered SI derived units.... s (radian Radian The radian is a unit of plane angle, equal to 180/pi Degree , or about 57.2958 degrees, or about 57?17'45?. It is the standard unit of angular measurement in all areas of mathematics beyond the elementary level.... and steradian Steradian The steradian is the SI unit of solid angle. It is used to describe two-dimensional angular spans in three-dimensional space, analogous to the way in which the radian describes angles in a Plane .... ) become derived units.
(1999)	new SI derived unit, the katal Katal The katal is the SI unit of catalysis activity. It is a derived SI unit for expressing quantity values of catalytic activity of enzymes and other catalysts.... = mole Mole (unit) The mole is a Units of measurement of amount of substance: it is an SI base unit, and one of the few units used to measure this physical quantity.... per second Second The second , sometimes abbreviated sec., is the name of a units of measurement of time, and is the International System of Units SI base unit of time.... , for the expression of catalytic activity.
(2003)	a comma or a dot on a line are reaffirmed as decimal marker symbols, and not as grouping symbols in order to facilitate reading; "numbers may be divided in groups of three in order to facilitate reading; neither dots nor commas are ever inserted in the spaces between groups". .
(2007)	clarification about the kelvin and thoughts about possible revision of certain base units

General Conference on Weights and Measures

CGPM Meetings

See also