IMPLEMENTATION AND PERFORMANCE EVALUATION OF A BROAD-BAND DIGITAL HARMONIC VECTOR VOLTMETER

A broadband digital harmonic vector voltmeter proposed previously and studied theoretically by the authors was implemented using a special-p urpose, random sampling strategy, to avoid the bandwidth limitations d ue to the finite conversion time of the sample-and-hold and analog-to- digital-conversion (S/H-ADC) devices. The experimental results have sh own that the bandwidth of the instrument is not limited by the finite conversion time of S/H-ADC devices, since good accuracy can be achieve d even when the average sampling frequency is much lower than the sign al bandwidth. The amplitude and phase uncertainty, with sinusoidal tes t signals up to 1 MHz and an average sampling rate of 10 kHz, was foun d to be lower than 3% and 0.03 rad, respectively. For more careful tes ting of the broadband performance of our instrument, we also carried o ut two-frequency, variable order harmonic measurements, which showed g ood accuracy (amplitude error less than 1.5% and phase error less than 0.03 rad) with harmonics up to 300 kHz, Reasonable accuracy (i.e., su fficient to correctly reconstruct the actual signal waveform) was also found with a highly distorted square-wave signal.