1. Sizes to be measured

The unit of electric current is the ampere, symbol A, one of the seven basic quantities of the international system of units. The current definition of the ampere is based on a fixed numerical value of the elementary charge, e, equal to 1.602 176 634 x 10 ^–19 when expressed in C (coulomb), a unit equal to A.s (ampere.second). This definition was adopted in November 2018 at the 26th meeting of the General Conference on Weights and Measures (CGPM), in Versailles.

The variation of an electric current can be continuous, alternating or pulsed.

Direct current is defined as a current whose value remains constant over time, or whose variations are negligible during the measurement period. In this case, a single parameter is sufficient to characterize it: its mean value....