Wideband Noncontact Voltage Measurement for EMC Applications: Design and Implementation

A methodology of amplitude and phase compensation for noncontact voltage measurements, which can be applied to wideband signal and noise observation in the electromagnetic compatibility (EMC) application, is presented. The noncontact techniques are based on a small amount of coupling capacitance between probe electrode and cable conductor where the observed signal is induced. In this case, a main technical issue to be overcome is the amplitude and phase error introduced by stray capacitance of the internal circuit, which needs to be resolved for application of the wideband EMC measurements. Herein, a design and implementation of phase compensation with inverting operational amplifier (OpA) configuration are discussed. Moreover, by introducing a system calibration with numerical process, validity for recovering the frequency response at 100 Hz–100 MHz is indicated. In the calibration process, frequency compensation for dielectric dispersion of the polyvinyl chloride (PVC) cable is also discussed. As for the time-domain measurement, the evaluation result of the fast transient impulsive noise of tr/tf: 10 ns emitted from a commercial power supply module is also discussed.