Coordination and collaboration
International Bureau of Weights and Measures (BIPM)

The reliability of the global measurement system is the result of international collaboration, and depends on the work carried out by each NMI to base its measurements and associated uncertainties on the SI, and to compare its realizations of SI units with those of other NMIs. To establish this equivalence, laboratories must regularly take part in measurement comparisons. In order to extend the practice of international comparisons, to substantiate their results with comprehensive documentation, and to provide objective evidence on which to base declarations of equivalence, the CIPM created a Mutual Recognition Arrangement, the CIPM MRA, in 1999.

The CIPM MRA is the structure enabling national metrology institutes...