General Conference on Weights and Measures

The General Conference on Weights and Measures (French: Conférence générale des poids et mesures – CGPM) is the senior of the three Inter-governmental organizations established in 1875 under the terms of the 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 (Metre Convention)^[1] was signed by 17 states. This treaty established the following organisations to conduct international activities relating to a uniform system for measurements:^[2]

• 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.

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]

Membership criteria

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^{[Note 1]} that only wish to participate in the MRA program. Associate members have observer status at the CGPM. Since all formal liaison between the convention organisations and national governments is handled by the member state's ambassador to France,^{[Note 2]} it is implicit that member states must have diplomatic relations with France,^[5] though during both world wars, nations that were at war with France retained their membership of the CGPM.^[6] The opening session of each CGPM is chaired by the French foreign minister and subsequent sessions by the Président de l'Académie des Sciences de Paris.^[7]

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 13 June 2017, there are 58 Member States and 41 Associate States and Economies of the General Conference (with year of partnership in parentheses):^[9]

Member States

Notes

Associates

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

CGPM meetings

See also

• Institute for Reference Materials and Measurements (IRMM)
• National Institute of Standards and Technology (NIST)
• National Conference on Weights and Measures (NCWM) United States

Notes

References