4. Current comparators

4.1 Principle

Designed to achieve very high accuracies, they are used, for example, as standards for precision testing of current transformers. There are a large number of possible versions of these devices, but they are all based on the same principle: comparison of primary and secondary currents by means of a current transformer and supply of the power required for the secondary Joule losses and the load by means of an auxiliary source, which may be a second current transformer (Figure 15 ), an electronic amplifier (Figure 16 ) or a combination of the two (Figure