Impedance Measurement Method Based on DFT

A principle of the impedance measurement based on DFT is proposed, and an implementation of the principle is designed. The principle raises the requirement of a 2-channel simultaneous sampling. In order to satisfy the requirement with a single A/D converter, both a hardware solution and a software solution are proposed, and the latter, which in fact is a kind of software compensation, is preferred. A larger measurement range requires a larger dynamic range of the data acquisition, and thus a floating-point A/D converter is designed to substitute for a monolithic fixed-point A/D converter, because the dynamic range of a FP-ADC is much larger than that of a fixed-point one. As a digital measurement technique, the method takes full advantage of the powerful arithmetic and processing ability of a digital signal processor. Simulation experiments on two extreme cases are studied to verify the performance of the measurement system and the result curves are plotted.