Rapid impedance spectroscopy using dual phase shifted chirp signals for electrochemical applications

Abstract

Impedance is an important diagnostic feature finding applications in material science, analytical chemistry, understanding biological systems etc. This is particularly true for diagnosis of electrochemical systems such as fuel cells and storage batteries. However the conventional technique for impedance measurement, i.e. Electrochemical Impedance Spectroscopy (EIS), is time intensive and requires sophisticated instrumentation making it unsuitable for online applications. This paper introduces a novel technique that makes use of two high bandwidth and short duration signals having dissimilar phases to estimate impedance. A unique class of signal, viz. the dual phase shifted chirp signal, which comprises two identical chirp signals having a known phase difference, is used to obtain the impedance profile. The technique is validated through both, simulation as well as experiments. The results obtained from this work are in correspondence with those obtained through conventional EIS, albeit in a minuscule fraction of time and with meagre instrumentation. The proposed technique will pave way for a quick and cost effective alternative to EIS and allow for impedance measurement during operation.