Low frequency impedance measurement using sine-fitting

Abstract

This paper describes an impedance measurement technique based on the use of a personal computer, two digitizing channels and the application of four-parameter sine-fitting algorithms to estimate amplitude, phase, offset and frequency of the voltages across the impedance under measurement and of a reference impedance. This simple and inexpensive setup leads to experimental results with accuracy comparable to those obtained with sophisticated high cost dedicated impedance measurement equipment. The results here presented, obtained using a low cost 12 bit PC data acquisition board, for impedances with amplitudes ranging from 100 Ω to 1 kΩ at 1 kHz, show relative standard deviations of the amplitude below 0.002% and standard deviations of the phase under 0.001°.