General conference of the weights and measures

The General conference of the weights and measures (CGPM) is the body decisional of the Convention of the Meter, charged to make the decisions as regards Métrologie and in particular with regard to the international Système of units (IF). Like the Convention of the Meter, it was created in 1875.

The conference gathers delegates of the Member States of the Convention of the Meter and associated states. The conference meets at present every four years, the two last meetings going back to 1999 and 2003. The first conference took place in 1889, that of 2003 being the 22e name. The conference meets in the buildings of the International office of the weights and measures (BIPM), with the Pavillon of Breteuil, Sevres (Parisian suburbs ).

At the time of each general conference, the members base themselves on the reports/ratios of the International committee of the weights and measures (CIPM) reporting completed works. They then make the adequate provisions for the extension and/or the improvement of the international System of units (IF), as well as general provisions and recommendations concerning metrology. The admistratives decisions relating to operation are also discussed of the BIPM.

Meetings of the CGPM and important decisions

1st (1889) - Sanction of the international prototypes of the Meter and the Kilogram.
2nd (1897) - (no resolution)
3rd (1901) - Definition of the Liter like volume occupied by the mass of 1 kilogram of pure water, with its maximum of density and under the normal atmospheric pressure ; assertion that the term of weight indicates a force and definition of the normal Accélération of the terrestrial Pesanteur with 980,665 cm/s 2 .
4th (1907) - (no resolution)
5th (1913) - (no resolution) International scales of temperature proposed. DO NOT APPEAR IN THE RESOLUTIONS --->
6th (1921) - (no resolution); Convention of the Meter revised.
7th (1927) - Precision on the definition of the meter by the international prototype Advisory committee of electricity (the CEC). It will become the Advisory committee of electricity and magnetism in 1997. TO PUT IN ADVISORY COMMITTEES --->
8th (1933) - Decisions relating to various prototypes of the meter and the kilogram; institution of the Advisory committee of photometry; substitution of the absolute electric units to the units known as “international”; reflection for the establishment of a standard of light.
9th (1948) - Reflection for a new definition; introduction of the Joule like unit of quantity of heat and use of the Point triples water like thermodynamic scale at only one fixed point; definition of the symbols of the units in force.
10th (1954) - Definition of the thermodynamic scale of temperature with the point triples water and Kelvin; definition of the Standard atmosphere; reflection for a new definition of the second; definition of the basic units of the international system * 11th (1960) - Reflection in order to define units and concepts used in the field of ionizing radiations; new definition of the Meter by a multiple a wavelength of radiation between two levels excited of the Krypton 86; new definition of the second like fraction of the Tropical year 1900; definition of the international system of units, of its basic units, its additional units and its derived units, as well as the multiples (until Téra) and submultiples (until Pico) of those; myria- and myrio- its withdrawn.
12th (1964) - Reflection for a new definition of the second by atomic processes; new definition of the liter as being one decimetre cubic exactly; definition of under multiples Femto and Atto; reflection in order to revise the international scales practices temperature of 1948.
13th (1967) - New definition of the second like duration of 9 192 631 770 periods of radiation corresponding to the transition enters the two hyperfine levels of the fundamental state of the atom of césium 133 ; the Degré Kelvin becomes the Kelvin; redefinition of the Candela; abandonment of the units Micron and new Candle.
14th (1971) - Reflection in order to obtain a definition of the international atomic Time; definition of the Mole as the quantity of matter of a system containing as many elementary entities than there are atoms in 0,012 kilogram of Carbone 12 .
15th (1975) - Reflection for a new definition of the amp; approval of the international scales practices temperature of 1968 amended in 1975; definition of the Becquerel and the Gray like unit for the ionizing rays; adoption of the prefixes Peta and Exa.
16th (1979) - Refédinition of the candela like luminous intensity, in a given direction, of a source which emits a monochromatic radiation of frequency 540' 1012 hertz and whose radiant intensity in this direction is 1/683 Watt by steradian ; definition of the Sievert like unit of equivalent of amount.
17th (1983) - the meter redefined starting from the Speed of light.
18th (1987) - Invitation to adopt conventional values for the constants of Josephson, K , and von Klitzing, R ; directives for the adoption of new international scales of temperature.
19th (1991) - Adoption of the conventional values of the constant of Josephson and von Klitzing with K = 483 597,9 GHz/V and R = 25 812,807 W; approval of the international scales of temperature of 1990; adoption of the prefixes Zetta, Yotta and Zepto, Yocto.
20th (1995) - Recommendation aiming in the long term obtaining a new definition of the unit of mass based on fundamental or atomic constants; abandonment of the class of the additional units Radian and Steradian, which becomes derived units.
21e (1999) - Reflection for a new definition of the unit of mass using fundamental constants; reflection for an extension of the international scales of temperature to the low temperatures (in lower part of 0,65 K); adoption of the Katal like measuring unit of the catalytic activity.
22e (2003) - Reaffirmation of the comma and the decimal point like decimal separators.

See too

External bonds

Presentation of the CGPM
Resolutions of the CGPM, 1889 to our days

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