Portable and Highly Versatile Impedance Meter for Very Low Frequency Measurements

Graziella Scandurra,Emanuele Cardillo,Carmine Ciofi,Gino Giusi,Antonella Arena

doi:10.3390/app11178234

Abstract

Electrical Impedance Spectroscopy (EIS) is a characterization technique that is gaining more and more importance in various fields of research and applications. The frequency range of investigation varies according to the type of application. In some fields (biology, medicine, energy) it is useful to be able to perform measurements at very low frequency values (down to a few mHz or even below). While impedance meters operating at frequencies in the range from a few tens of Hz up to a few MHz can be regarded as quite standard pieces of instrumentation commonly available in many laboratories, instrumentation for measurements at very low frequencies, although commercially available, is less common. The subject of this work is the design, realization and testing of a low frequency impedance measurement platform that has the advantage of being portable, rather inexpensive, and yet highly versatile. In our approach, we exploit a personal computer and a soundboard as a powerful system for digital signal generation and analysis that, with the help of low complexity and low-cost external hardware and a public domain software for the implementation of the core system, allow to tailor the platform for targeting specific applications with minimal effort. As an example, we will demonstrate the application of the system to the investigation of polypyrrole-based supercapacitor structures.

Highlights

By reducing the hardware complexity, the system can be more reproduced by researchers interested in its application. This is why we investigated in the first place the possibility of resorting to a standard audio board for signal generation and acquisition with a personal computer acting as a powerful platform for digital signal elaboration
Sci. 2021, 11, 8234 more reproduced by researchers interested in its application
We developed a simple library for the software implementation of sinusoidal Numerically Controlled Oscillators (NCOs), while for the analysis of the acquired signals and the extraction of the admittance of the Device Under Test (DUT) we relied on the Narrow Band (NB) estimation extension of the QLSA public domain library [35,36]

Summary

Introduction

For example, EIS (or BIS, Biological Impedance Spectroscopy) has proven to be an effective technique for non-invasive analyses and diagnosis of the healthy condition of subjects in a few medical fields [1,2,3,4,5,6,7,8] and it seems to be appropriate for the characterization of the physicochemical properties of pharmaceutical materials [9] and of bacteria [10,11,12] and viruses [13,14]. This implies that bio-impedance measurements have so far neglected the effects due to the so-called α dispersion [16], which takes into account the relaxation of ions surrounding the charged cellular membrane and which dominates the impedance behavior from 0 Hz to a few hundred Hertz

Methods

Results

Conclusion