Circuit with nonlinear transformer allowing DC current measurements via an isolation gap

A sensor circuit allowing the measurement of DC current via an isolation gap is investigated. The primary coil of a nonlinear transformer and an operational amplifier are connected into an RL-multivibrator circuit. The measured DC current is applied to the secondary of this transformer. The DC voltage at the inverting mode of the operational amplifier gives information on the polarity and value of the measured current. The sensor transfer characteristics are calculated using piecewise approximation of the core magnetization characteristic, and experimentally verified.<<ETX>>