A low-current multistage clamp-on current transformer with ratio errors below 50×10-6

An electronically aided multistage technique is applied to a hand-held openable-core damp-on current transformer which enables accurate low current measurements to be made over a wide dynamic and frequency range of operation, for use in conjunction with highly accurate active/reactive power and energy meters, and harmonic power analyzers. The clamp on current transformer can be used to measure currents in the range from 1 A to 200 A, at frequencies between 50 Hz ad 5 kHz, with ratio errors of less than 50×10^-6 in both magnitude and phase