Abstract
Electrochemical Impedance Spectroscopy (EIS) is a widely used electrochemical measurement technique
that has been used in a great spectrum of
fields since it allows deconvolving the individual physic-
chemical processes that take place in a given system. Ohms generalized law, and thus the impedance
concept, are only valid if 4 conditions are fulfilled: causality,
finiteness, stationarity and linearity. In the
case that any of these conditions is not achieved, the obtained impedance spectra will present distortions
that may lead to biased or even erroneous results and conclusions. For this reason it is crucial to verify if
the 4 conditions are fulfilled, before accepting the results extracted from impedance spectra. In this work,
a linearity assessment quantitative method based in the total harmonic distortion (THD) parameter is
presented and verified experimentally. The experimental validation of the implemented method showed
that the implemented method is able to assess quantitatively the linearity of the system. In addition, it is
also able to determine the threshold frequency above which the system will not present significant
nonlinear effects even for large perturbation amplitudes. It was observed that the THD method is more
sensitive to nonlinear effects than the spectra themselves.
