Sensitivity and drift value measurement of DC current comparator

In order to improve the measurement performance characterized by sensitivity and drift value of DC current comparator, this paper analyzed two kinds of differential structure of cores; constructed the sensitivity and drift value measurement device formed by excitation voltage source, DC current source, oscilloscope, peak difference demodulation circuit and voltage meter. Through formula derivation, it was proved that the excitation winding can play the role of detection winding and the output voltage is still an even harmonic function. This simplified structure can reduce the leakage flux of excitation winding and accordingly improve the accuracy of current ratio. Meanwhile, pairs of ten winded cores with the material permalloy were tested. 45 groups of measurement results show that the top sensitivity is 7mV/μAT and the minimum drift value in 10 minutes is 3μAT; however, some cores with obvious differences in magnetic properties lead to the matching failure and no data were measured, characterized by clear dispersion.