2. Zeroing methods applied to resistance measurement

2.1 Standard resistors (connection and ohm conservation)

Standard resistors are used to connect to the national unit, and to maintain this unit between two successive connections. The first function is ensured by regular (e.g. annual) calibration in one of the accredited laboratories of the BNM-COFRAC national calibration chain; the second function consists in comparing the laboratory's working standards with the connection standard, using one of the zero methods described below.

The use of different elements, for routine measurements and for connection to national standards, considerably reduces the risk of accidental variations in standards (resulting from shocks, electrical overloads, etc.); it also makes it possible to remove any doubt about the value of...