General Conference on Weights and Measures

For a topical guide to this subject, see Outline of the metric system.

The General Conference on Weights and Measures (Metre Convention (French: Convention du Mètre) to represent the interests of member states. The treaty, which also set up two further bodies, the International Committee for Weights and Measures (French: Comité international des poids et mesures- CIPM) and the International Bureau of Weights and Measures (French: Bureau international des poids et mesures - BIPM), was drawn up to coordinate international metrology and to coordinate the development of the metric system.

The conference meets in Sèvres (south-west of Paris) every four to six years. Initially it was only concerned with the kilogram and the metre, but in 1921 the scope of the treaty was extended to accommodate all physical measurements and hence all aspects of the metric system. In 1960 the 11th CGPM approved the Système International d'Unités, usually known as "SI".

Establishment

On 20 May 1875 an international treaty known as the Convention du Mètre (

References

Notes

• International Bureau of Weights and Measures (BIPM)
• International Committee for Weights and Measures (CIPM)
• Institute for Reference Materials and Measurements (IRMM)
• National Institute of Standards and Technology (NIST)

See also

CGPM meetings

At its 21st meeting (October 1999), the CGPM created the category of "associate" for those states not yet members of the BIPM and for economic unions.^[10]

Associates

Notes

Member States

Of the twenty countries that attended the Conference of the Metre in 1875, representatives of seventeen signed the convention on 20 May 1875.^{[Note 3]} In April 1884 HJ Chaney, Warden of Standards in London unofficially contacted the BIPM inquiring whether the BIPM would calibrate some metre standards that had been manufactured in the United Kingdom. Broch, director of the BIPM replied that he was not authorised to perform any such calibrations for non-member states. On 17 September 1884, the British Government signed the convention on behalf of the United Kingdom.^[8] This number grew to 21 in 1900, 32 in 1950, and 49 in 2001. As of 7 August 2013, there are 55 Member States and 38 Associate States and Economies of the General Conference (with year of partnership in parentheses):^[9]

^[7].Président de l'Académie des Sciences de Paris The opening session of each CGPM is chaired by the French foreign minister and subsequent sessions by the ^[6] though during both world wars, nations that were at war with France retained their membership of the CGPM.^[5] it is implicit that member states must have diplomatic relations with France,[Note 2] that only wish to participate in the ^{[Note 1]} The CGPM recognises two classes of membership - full membership for those states that wish to participate in the activities of the BIPM and associate membership for those countries or economies

Membership criteria

The CGPM acts on behalf of the governments of its members. In so doing, it appoints members to the CIPM, receives reports from the CIPM which it passes on to the governments and national laboratories on member states, examines and where appropriate approves proposals from the CIPM in respect of changes to the International System of Units (SI), approves the budget for the BIPM (over €10 million in 2012) and it decides all major issues concerning the organization and development of the BIPM.^[3][4]

• Conférence générale des poids et mesures (CGPM), an intergovernmental conference of official delegates of member nations and the supreme authority for all actions;
• Comité international des poids et mesures (CIPM), consisting of selected scientists and metrologists, which prepares and executes the decisions of the CGPM and is responsible for the supervision of the International Bureau of Weights and Measures;
• Bureau international des poids et mesures (BIPM), a permanent laboratory and world centre of scientific metrology, the activities of which include the establishment of the basic standards and scales of the principal physical quantities and maintenance of the international prototype standards.

[2]