

Since the French Revolution, and the development of the decimal metric system, metrology has developed strongly throughout the world. The guarantee of reliable and recognized measurements, the evolution of technologies, imply having authorities at the highest level that examine and propose solutions in the field of measurement. How is metrology organized at the international level? Which bodies are responsible for defining units and developing measurement standards? Here are some answers.
The Metre Convention, a diplomatic treaty, was signed on 20 May 1875 by 17 member states. The purpose of this convention is to promote the decimal metric system. Following this convention, a scientific bureau, the Bureau International des Poids et Mesures (BIPM), was created.
As of 20 May 2019, the number of member states is of 60 countries, including 29 countries on the European continent.
In order to facilitate the integration of new States, in particular for participation in the CIPM MRA, countries are associated with the General Conference on Weights and Measures (CGPM). These countries have no voting rights in the CGPM. As of 7 August 2018, 42 States or economies have signed the association with the CGPM.
It should be noted that the President of the CIPM, the Vice-President of the CIPM, the Secretary of the CIPM and the Director of the BIPM must be of different nationalities.
It is the desire to work together for the advancement of science that leads Member States to join the Metre Convention, not only in their own interest, but also in recognition of the necessity for all countries to participate in a work of global progress from which they too will benefit.
The CGPM, a diplomatic conference which brings together the delegates of the Member States of the Metre Convention, meets at least once every six years at the invitation of the French Ministry of Foreign Affairs. Currently, and since 1960, meetings of the CGPM are held approximately every four years.
The opening session is chaired by the French Minister of Foreign Affairs and the working sessions by the President of the Paris Academy of Sciences.
The CIPM meets at least once a year. It is composed of eighteen eminent personalities, scientists and metrologists of different nationalities, elected in their personal capacity by the CGPM. France, holder of the diplomatic treaty, de facto has a seat on the CIPM.
In view of the ever increasing number of new Member States, and as a result of new and numerous scientific and technical works developed by the National Metrology Institutes (NMIs), the CIPM has, since 1927, set up a series of Consultative Committees (CCs) to study in greater depth scientific and technical progress that may have a strong influence on metrology.
The Consultative Committees are composed of international experts and specialists from the National Metrology Institutes. The CCs are usually chaired by a member of the CIPM.
Ten CCs have been created up to this day:
The BIPM, located at the Pavillon de Breteuil in Sèvres (France), is a scientific metrology laboratory whose essential mission is to ensure uniformity of measurements throughout the world (both physical and chemical). The Director of the BIPM is appointed by the CGPM.
The BIPM carries out fundamental research to improve reference standards in collaboration with the National Institutes of Metrology (NMIs), to participate in and organize international comparisons, and to maintain the reference standards for which it is responsible.
The operation of the BIPM is ensured by the contributions paid by each Member State participating in the Metre Convention. The annual allocation to the BIPM, as defined in the CGPM, is distributed among States according to a scale based on the coefficients of the United Nations scale, but with maximum limits of 10% and minimum limits of 0.5% of the total allocation.
All States contributing to the maintenance of the BIPM are co-owners of its facilities.
Preamble: a generic term refers to the national body in charge of scientific and technical metrology in each country: National Institute of Metrology (NMI). Depending on its structure and organisation, each country may be composed of several national metrology laboratory, one NMI (in France, LNE) and designated laboratories, the DIs (in France, LNE-LNHB, LNE-LCM, LNE-SYRTE, LNE-CETIAT, LNE-ENSAM, LNE-IRSN, LNE-LADG, LNE-LTFB, LNE-Trapil).
Several factors have led to the creation of regional metrology organizations (RMOs):
The first RMOs were created in the 1970s and 1980s:
The active members in these regions are the NMIs and DIs of the countries that have joined the region. Associate members are also accepted by RMOs, or corresponding members, especially for countries that are in areas where no region has yet been established.
To date, RMOs have grown exponentially, and their role in the international metrology scene has undoubtedly increased. RMOs play an essential role in the implementation of the Metre Convention.
The Mutual Recognition Arrangement (MRA) was drafted by the International Committee for Weights and Measures (CIPM) under the authority conferred upon it by the Member States of the Metre Convention, and signed in October 1999 by the directors of the NMIs.
The CIPM MRA establishes mutual recognition of national measurement standards and calibration and measurement certificates (Calibration Measurement Capabilities - CMCs) issued by their laboratories.
To establish the criteria for mutual recognition on an objective basis, this arrangement is based on:
This arrangement consists of two parts: in the first part, the Parties recognize the degree of equivalence of the national measurement standards of the participating laboratories; in the second part, the Parties recognize the validity of the calibration and measurement certificates issued by the participating laboratories. A specific logo has been created, which can be applied to calibration certificates issued by NMIs or DIs, for CMCs published in the KCDB (BIPM Key Comparison DataBase).
The directors of the NMIs that sign the MRA do so with the approval of the appropriate authorities in their country. By the same token, they:
A database containing the results of key comparisons of national measurement standards and lists of calibration and measurement capabilities of NMIs is available on the BIPM website, the KCDB (BIPM Key Comparison DataBase).
OIML (Organisme International de Métrologie Légale) is an intergovernmental organization created in 1955 whose general objective is the coordination and harmonization at the international level of administrative and technical regulations on measures and instruments of measures promulgated by the various countries. OIML has 62 Member States and about 65 corresponding members. OIML is recognized as an international standardization body by the World Trade Organization.
The aim of this harmonisation is to facilitate trade between countries not only in measuring instruments but also in all operations involving measurements. To this end, the OIML draws up international recommendations.
The OIML operates with a permanent office located in Paris and called the Bureau International de Métrologie Légale (BIML). This office centralizes the work carried out by the technical offices in the member countries and coordinates all OIML activities.
The International Conference on Legal Metrology, with diplomatic status. This conference, which brings together the Member States every four years, is responsible for taking fundamental decisions concerning the OIML, in particular its budget, its working policy and the formal adoption of the International Recommendations;
The International Committee for Legal Metrology (CIML) follows the technical work and approves the recommendations before their adoption by the International Conference. These recommendations were developed by the Technical Working Groups. CIML members are responsible for the national legal metrology services of OIML Member States. The CIML elects a President from among its members;
The Presidency Council, a group convened by the President of the CIML, whose mission is to assist the latter in strategic reflections on the development of the OIML
The official languages of the OIML are French and English.
BIML publishes a specialized journal: "Le Bulletin de l'Organisation Internationale de Métrologie Légale".
IMEKO was founded in 1958. It is a federation of metrology societies and universities that feel concerned by all types of measures (scientific, technological and/or industrial).
Currently IMEKO has 42 member organisations (for 42 countries). IMEKO's objective is to:
In order to cover as widely as possible the problems related to measurements that can be carried out in laboratories, IMEKO has organized itself into technical committees: TCs. At present 24 TCs have been created.
The Collège Français de Métrologie (CFM) is the French member of IMEKO, and as such participates in the General Council. The CFM also has representatives on some of the IMEKO technical committees.
The 24 technical committees are as follows:
EURAMET e.V. is an organisation, officially created on 11 January 2007.
It is the regional metrology organization (RMO) for Europe, of which France is a member. Within the framework of the CIPM Mutual Recognition Arrangement for Calibration and Measurement Certificates, the CIPM MRA, EURAMET e.V has delegated certain actions (in particular reviews of the quality management systems of each member state).
EURAMET e.V. follows on from the EUROMET association founded in Madrid in September 1987. EUROMET originally included the national metrology institutes of the countries of the European Union and the European Free Trade Association (EFTA). It then integrated, as and when they joined, the new member countries of the European Union. Other countries, not yet members of the European Union at that time, were also full members of EUROMET, such as Turkey and Serbia, for example. EUROMET was dissolved in June 2007, and all its activities were transferred to EURAMET.
EURAMET e.V. is a non-profit association under German law. It currently comprises 37 member countries of the European Union, EFTA countries and states wishing to join the European Union.
EURAMET was set up to develop cooperation of all kinds between the national metrology institutes of Western Europe (NMIs) and to ensure efficient use of available metrology resources. Since its creation, EURAMET has focused on cooperation in research and development.
The objectives of the association are numerous, we will quote the following:
Each signatory member (for France, the LNE) mandates one delegate. All delegates constitute the EURAMET General Assembly. It meets at least once a year to discuss the objectives and strategy to be developed within the European Metrology Association.
The President of EURAMET is elected for three years by the General Assembly. His mandate is not renewable; he is assisted by a secretariat and two vice-presidents, also elected by the General Assembly.
The First Vice-President is dedicated to EURAMET's own activities.
The Second Vice-President is appointed Chairman of the EMPIR Committee (European Metrology Programme for Innovation and Research). Each member country of the EMPIR Committee shall appoint a representative to participate in the Committee. To date, 28 countries out of EURAMET's 37 members participate in the EMPIR programme.
A Board of Directors (BoD), composed of nine members (including the President and his 2 Vice-Presidents, and 6 other members elected among the delegates of the General Assembly) ensure the functioning of the latter between two General Assemblies, and assist the President in his function.
Furthermore, EURAMET has become more professional with a multi-component office in order to better respond to the various activities of the association: legal and financial aspects, procedures and specific follow-up of research projects within the EMPIR framework (JRPs - Joint Research Project), projects financed by the European Union, activities linked to projects defined within the technical committees, quality assurance management in laboratories, inter-laboratory comparisons, etc.
To ensure EURAMET's technical activity, specific groups have been created: Technical Committees (TCs). There are currently twelve of them, 10 of which relate to technical activities and 2 to transverse activities:
Each EURAMET member country may designate a "contact-person", specialist in the field concerned, to represent it on each of the technical committees. For each TC, a TC Chairperson is elected by all the Contact Persons of the TC concerned; his term of office is two years, renewable once. Its main tasks are the coordination of the projects presented by the contact persons and the animation of the Technical Committee.
Given the volume of activity of some committees, but also the technical diversity of these areas, some TCs have been subdivided into sub-groups. This is for example the case for electricity with subcommittees in low frequency, quantum metrology, power and radio frequencies.
Each collaboration project, of a specific domain, is classified in one of the following categories:
Currently, around 1000 projects have been initiated in 20 years by EUROMET. The substantial number of projects is proof of EUROMET's, and now EURAMET's, success in terms of European collaboration in research and knowledge transfer.
With the implementation of the CIPM MRA, the projects on inter-laboratory comparisons had an unprecedented growth in the following 5 years. These comparisons are used to demonstrate the equivalence of national standards. Collaborations for joint research and development projects is the most appreciated type of collaboration; this indicates the obvious willingness of metrologists to share their work.
Research is very expensive and requires considerable resources, both human and in terms of the most sophisticated equipment. Since redundancy is also essential in metrology, particularly at the highest level of implementation, it must be reconciled with a fair optimization of the means implemented. EUROMET made it possible to generate joint research and development projects, based on voluntary partnership and on the own funds of each participating country. With new and growing areas of metrology, such as nanosciences, biotechnology, medicine, software and modelling, materials, health, imaging, perception metrology, security and space, and many others, additional resources were needed.
The European Union, aware of these challenges, has proposed to develop and finance a metrology research programme, for better synergy and greater scientific cooperation between States in Europe. Several steps were necessary.
The themes of the projects financed are defined by the EMPIR Committee and present important societal or economic issues such as health, the environment, energy, industrial needs, new technologies or the fundamental aspect of redesigning the international system of units.