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International reach

Worldwide metrology

International trade and research relies on co-operation on measurement standards

International co-operation in action

The Metre Convention (Convention du Mètre), signed in Paris on 20 May 1875 by representatives of 17 nations and modified slightly in 1921, remains the basis of international agreement on units of measurement. Today, there are 64 Member States of the Metre Convention and 36 Associate States and Economies. The Convention created an intergovernmental organisation, known as the International Bureau of Weights and Measures (Bureau International des Poids et Mesures, BIPM), that co-ordinates international metrology and the development of the metric measurement system. Its work is supervised by the International Committee for Weights and Measures (Comité International des Poids et Mesures or CIPM). The BIPM and CIPM guided the development of the international metrology system in operation today, the introduction of the SI system in 1960 and the establishment of the CIPM Mutual Recognition Arrangement in 1999. 

The CIPM is responsible for oversight of the CIPM Mutual Recognition Arrangement (CIPM MRA). Through its system of peer review, intercomparisons and Calibration and Measurement Capabilities (CMCs) this arrangement provides the basis for recognising the degree of equivalence of the standards maintained by NMIs and mutual recognition of the calibration and measurement certificates that they issue. This provides the basis for recognition of equivalence of other measurements made in society provided that they are traceable to an NMI. The Arrangement is supported by 10 CIPM Consultative Committees made up of technical experts from NMIs, DIs and appropriate scientific bodies. 

Regional Metrology Organisations (RMOs) are made up of NMIs from the same part of the world. RMOs coordinate activities between its members and also between other RMOs. The RMO for European NMIs is EURAMET and NPL is an active member of this organisation. NPL is also an Associate Member of the Asia-Pacific Metrology Programme (APMP), which is a reflection of its growing interests in that region.

EURAMET’s mission is to develop and disseminate an integrated, cost-effective and internationally competitive measurement infrastructure for Europe, taking into account the needs of industry, business and governments. Bringing European NMIs and DIs together, the organisation supports members to meet their national requirements and to establish a balanced European measurement infrastructure. As one of 6 Regional Metrology Organisations EURAMET has a role in implementing the CIPM MRA. This is done through several Technical Committees, most of which include an NPL representative. There are two other main tools that EURAMET uses to achieve its goals. The first is a series of European metrology research programmes funding collaborative research projects (EMRP, EMPIR and now The Partnership on Metrology). The second tool is a number of European Metrology Networks (EMN) which provide an interface between the metrology community and stakeholders in academia, regulatory bodies and business. NPL is the UK member of EURAMET and an active participant in European research projects and EMN. The Management Support Unit for EURAMET/EU funded metrology research programmes is hosted at NPL.  


Accreditation is the independent evaluation of conformity assessment bodies against recognised standards to carry out specific activities to ensure their impartiality and competence. Through the application of national and international standards, government, procurers and consumers can have confidence in the calibration and test results, inspection reports and certifications provided. NPL is an accredited organisation to the United Kingdom Accreditation Service (UKAS) which is a signatory to the ILAC Mutual Recognition Agreement. 

International Laboratory Accreditation Cooperation (ILAC) is the international organisation for accreditation bodies operating in accordance with ISO/IEC 17011 and involved in the accreditation of conformity assessment bodies including calibration laboratories and testing laboratories (using ISO/IEC 17025), medical testing laboratories (using ISO 15189), inspection bodies (using ISO/IEC 17020) and Certified Reference Material (CRM) producers (using ISO 17034). 

UKAS is the UK’s National Accreditation Body, responsible for determining, in the public interest, the technical competence and integrity of organisations such as those offering testing, calibration and certification services. 

Global collaboration

The International Organization for Standardisation (ISO) is an independent, non-governmental international body with a membership of 162 national standards bodies. BSI, as the UK's national standards body, is a member. 

The International Organization of Legal Metrology (OIML) aims to put in place effective legal metrology infrastructures that are mutually compatible and internationally recognised and to facilitate trade, establish mutual confidence and harmonise the level of consumer protection worldwide. Legal metrology is the application of legal requirements to measurements and measuring instruments. In the UK Legal metrology is the responsibility of the office for Product Safety and Standards (OPSS).

WELMEC is a body set up to promote European cooperation in the field of legal metrology and develop and maintain mutual acceptance among its members. It maintains effective cooperation to achieve a harmonised and consistent approach to the societies needs for legal metrology and for the benefit of all stakeholders including consumers and businesses. 

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