General Conference on Weights and Measures facts for kids

The General Conference on Weights and Measures (called CGPM for short, from its French name Conférence générale des poids et mesures) is the main authority for the International Bureau of Weights and Measures (BIPM). The BIPM is an international group started in 1875 by the Metre Convention. Its job is to help countries work together on measurement science and measurement standards. The CGPM includes representatives from member governments and observers from other partner countries. It chooses the International Committee for Weights and Measures (or CIPM, from Comité international des poids et mesures). The CIPM then guides and oversees the BIPM.

At first, the Metre Convention only dealt with the kilogram and the metre. But in 1921, its work grew to include all physical measurements and everything about the metric system. In 1960, the 11th CGPM approved the International System of Units, which we usually call "SI."

The General Conference gets reports from the CIPM about their work. They talk about how to make the International System of Units (SI) better and spread its use. They also approve new scientific findings about measurements and make big decisions about how the BIPM is run and how it grows, including its money.

The CGPM usually meets in Paris every four years. The 25th meeting was from November 18 to 20, 2014. The 26th meeting was in Versailles from November 13 to 16, 2018. The 27th meeting happened from November 15 to 18, 2022.

How the CGPM Was Started

On May 20, 1875, 17 countries signed an international agreement called the Convention du Mètre (the Metre Convention). This agreement created an international organization, the Bureau international des poids et mesures (BIPM). This organization has two main parts:

• The Conférence générale des poids et mesures (CGPM): This is a big meeting of official representatives from member countries. It is the highest authority for all decisions.
• The Comité international des poids et mesures (CIPM): This group is made up of elected scientists and metrologists. They prepare and carry out the decisions made by the CGPM. They also supervise the organization.

The BIPM has a permanent lab and office. Its work includes setting up basic standards for important physical measurements. It also keeps the international prototype standards safe.

The CGPM works for the governments of its member countries. It chooses members for the CIPM and gets reports from the CIPM. These reports are then shared with the governments and national labs of member countries. The CGPM also checks and approves changes to the International System of Units (SI). It approves the BIPM's budget (which was over €13 million in 2018). It also makes all the big decisions about how the BIPM is organized and developed.

You can think of the structure like a company. The BIPM is the company. The CGPM is like the meeting of all the shareholders (owners). The CIPM is like the board of directors chosen by the shareholders. The staff at the BIPM's location in Saint-Cloud do the daily work.

Who Can Join?

The CGPM has two types of members:

• Full members: These are countries that want to take part in all the BIPM's activities.
• Associate members: These are countries or economies that only want to join the CIPM's MRA program. Associate members can observe the CGPM meetings.

To be a full member, a country usually needs to have diplomatic relations with France. This is because all official communication between the organization and national governments goes through the country's ambassador to France. Even during world wars, countries fighting France kept their membership in the CGPM. The meetings are led by the President of the French Academy of Sciences.

In 1875, 20 countries attended the first Conference of the Metre, and 17 signed the agreement. In 1884, the British Government signed the convention for the United Kingdom. By 1900, there were 21 members. This number grew to 32 in 1950 and 49 in 2001. As of November 18, 2022, there are 64 Member States and 36 Associate States and Economies.

Member states

Former members

Associates

In October 1999, at the 21st CGPM meeting, a new "associate" category was created. This was for countries not yet full BIPM members and for groups of economies.

Former Associates

CGPM Meetings and Decisions

The CGPM meetings are where important decisions about measurements are made. Here are some key moments:

International Committee for Weights and Measures (CIPM)

The International Committee for Weights and Measures (CIPM) has eighteen members, each from a different country. They are chosen by the General Conference on Weights and Measures (CGPM). Their main job is to make sure that units of measurement are the same all over the world. They do this by taking direct action or by suggesting ideas to the CGPM.

The CIPM meets every year (since 2011, twice a year) at the Pavillon de Breteuil. During these meetings, they discuss reports from their special Consultative Committees. Reports from the CGPM, CIPM, and all Consultative Committees are published by the BIPM.

What the CIPM Does

The main office (or secretariat) is in Saint-Cloud, Hauts-de-Seine, France.

In 1999, the CIPM created the CIPM Arrangement de reconnaissance mutuelle (Mutual Recognition Arrangement, or MRA). This agreement helps countries accept each other's national measurement standards. It also recognizes that calibration and measurement certificates from national metrology institutes are valid.

Recently, the CIPM has focused on updating the SI.

Consultative Committees

The CIPM has set up several consultative committees (CC) to help with its work. These committees are guided by the CIPM. The head of each committee is usually a member of the CIPM. Most committees are open to National Metrology Institutes (NMIs) from member countries that are experts in that field. NMIs from other member countries can attend as observers if they are active in the field but not yet experts.

These committees include:

• CCAUV: Consultative Committee for Acoustics, Ultrasound and Vibration
• CCEM: Consultative Committee for Electricity and Magnetism
• CCL: Consultative Committee for Length
• CCM: Consultative Committee for Mass and Related Quantities
• CCPR: Consultative Committee for Photometry and Radiometry
• CCQM: Consultative Committee for Amount of Substance – Metrology in Chemistry and Biology
• CCRI: Consultative Committee for Ionizing Radiation
• CCT: Consultative Committee for Thermometry
• CCTF: Consultative Committee for Time and Frequency
• CCU: Consultative Committee for Units

The CCU's job is to give advice on how the SI should be developed and to help create the SI brochure. It also works with other international groups like the ISO, IAU, IUPAC, IUPAP, and CIE.

Important Reports

The CIPM publishes official reports, such as:

• Reports of CIPM meetings (called Procès-Verbaux)
• An annual report to governments about the BIPM's money and management
• Information about how much each member country needs to contribute
• Invitations to CGPM meetings
• A report from the President of the CIPM to the CGPM

Sometimes, the CGPM asks the CIPM to do big studies about things that affect the CGPM or the BIPM. Here are some of those reports:

The Blevin Report

The Blevin Report, published in 1998, looked at the state of measurement science around the world. The report came from a decision made at the 20th CGPM meeting in 1995. The CIPM was asked to

study and report on the long-term national and international needs relating to metrology, the appropriate international collaborations and the unique role of the BIPM to meet these needs, and the financial and other commitments that will be required from the Member States in the coming decades.

The report found that the BIPM needed to work more closely with other organizations like the International Organization of Legal Metrology (OIML) and the International Laboratory Accreditation Cooperation (ILAC). It also highlighted the need for cooperation between different labs and for involving developing countries in the world of metrology.

The Kaarls Report

The Kaarls Report, published in 2003, looked at the BIPM's role in the changing needs for measurement science in trade, industry, and society.

SI Brochure

The CIPM is responsible for the SI brochure, which formally defines the International system of units. The CCU creates this brochure with help from other international organizations. At first, the brochure was only in French, the official language of the Metre Convention. But newer versions are published in both English and French at the same time, with the French text being the official one. The 6th edition came out in 1991, the 7th in 1998, and the 8th in 2006. The most recent is the 9th edition. Version 1 was published in 2019 to include the 2019 redefinition of the SI base units (also known as "new SI"). It was updated to version 2 in December 2022 to include the new SI prefixes ronna-, quetta-, ronto-, and quecto- that were added in November 2022.

See also

In Spanish: Conferencia General de Pesas y Medidas para niños

• History of the metre
• Institute for Reference Materials and Measurements (IRMM)
• National Institute of Standards and Technology (NIST)
• National Conference on Weights and Measures (NCWM) United States
• Outline of the metric system
• Seconds pendulum