Key comparisons of National Measurement Standards

The mutual recognition of national measurement standards is of fundamental importance as a supporting member of a modern structure of international trade in goods and services. Calibration and testing services, accreditation bodies and users of these services must have confidence that the national measurement standards upon which their work is based are indeed equivalent. A set of key comparisons of national measurement standards is the technical basis for the mutual recognition agreement drawn up by the Comite International des Poids et Mesures (CIPM) and soon to be signed by the directors of nearly forty national metrology institutes (NMI). This presentation describes how the CIPM´s Consultative Committees (CC) choose key comparisons and how they are carried out by national metrology institutes or by the Bureau International des Poids et Mesures (BIPM). This can be done (1) under the auspices of the Consultative Committees, (2) under the auspices of regional metrology organization (RMO), or simply (3) as bilateral comparisons between two institutes; but always under a set of general guidelines. The presentation describes how key comparison results are discussed and examined by the Consultative Committees and how, after approval, they will be listed in a freely available key comparison database