THD: parameters affecting its value & comparison with other methods of linearity assessment – Battery & Corrosion – Application Note 65

Abstract

This application note develops some aspects of the Total Harmonic Distortion as an indicator of EIS quality. After presenting the main factors affecting the THD, a comparison with other methods of non-linearity assessment, namely the Lissajous plot, Kramers-Kronig transform, and the model-based method, is presented.

Introduction

New EIS quality indicators were introduced since EC-Lab®11.20 and described in [1]:

. Total Harmonic Distortion (THD)
. Non-Stationary Distortion (NSD)
. Noise to Signal Ratio (NSR)

The THD is used to quantify the distorsion of the response of a system, which can be used to characterize its linearity. Other methods have been proposed for this purpose:

. Lissajous plot
. Kramers-Kronig (KK) transform
. Model-based method.

In this note, we will first give further details about non-linearity and the THD indicator and secondly give a few comparison elements with other non-linearity indicators, based on results obtained on Bio-Logic Test Box-3.

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