(BIPM) The standards body that ensures world-wide uniformity of measurements and their traceability to the International System of Units (SI). The BIPM is based in France and operates with the authority of the Convention of the Metre, a diplomatic treaty between fifty-one nations. It operates through a series of committees, whose members are the national metrology laboratories of the member states of the convention, and through its own laboratory work. The BIPM carries out measurement-related research. It takes part in, and organises, international comparisons of national measurement standards, and it carries out calibrations for member states.