Impedance Measurements using Analog to Digital Converters and Ellipse Fitting Signal Processing Algorithms

Abstract

In this paper, the measurement of impedances using analog to digital converters and ellipse fitting signal processing algorithms is described. The robustness of this new method makes it specially suited for low frequency impedance measurements (up to 1 MHz) in portable DSP based instruments. Previous methods relied on sine-fitting algorithms to estimate the sine parameters together with the signal frequency. These were iterative algorithms where convergence is not assured and they can be a significant computational burden requiring more processing capabilities in the instrument. With ellipse fitting, the frequency is not estimated and the algorithm is not iterative.