A current transfer method and its application to calibrating a current comparator

Current transfer by switching a comparison winding from a series to a parallel connection allows the error of an n:1 ratio comparator to be determined by self-calibration at a 1:1 ratio. The magnetic errors are shown to be the same for either comparison winding connection. The technique is limited to frequencies at which the magnetic error considerably exceeds the admittance error, i.e. typically up to several hundred hertz. The frequency range for which the method can be applied depends on the distribution of admittances to ground as well as the interwinding and shunt admittances, which cause the admittance error for a series section connection to be different from its value for a parallel section connection. The error characteristic also depends on resonances in the inductance circuits appearing in the comparator, on capacitances to ground, and on the interwinding and shunt capacitances