Each State has its own metrology infrastructure. In most cases the BIPM interacts principally with one National Metrology Institute (NMI) per State, as nominated through the State's Foreign Affairs Department. That NMI is responsible for coordinating with any other institutes (NMIs or others) that make up that nation's metrology system.
The dropdown menu on the right-hand side of this page gives access to more details about the metrology infrastructure in individual Member States and Associates. In particular, these pages list all the institutes participating in the CIPM Mutual Recognition Arrangement (CIPM MRA),
the international framework through which the NMIs demonstrate the equivalence of their measurement standards and the calibration and measurement certificates they issue.
The BIPM hosts (approximately annual) meetings of the Directors of NMIs, providing a unique occasion for discussion of metrological issues of world-wide concern, and of course for discussion of the BIPM's work programme. Such meetings sometimes also include governmental representatives from Member States, to allow discussion of the financial implications.