Resistance Comparisons at Nanovolt Levels Using an Isolating Current Ratio Generator

Abstract

A circuit has been developed for the generation of isolated currents having precisely defined ratios. It can be used to compare resistances with accuracies up to 0.03 ppm and with sensitivities as low as 1 nV. When comparisons are made using low frequency currents, thermal emf's are eliminated. Several variations of the circuit which can be made easily in the laboratory are described.