Broadband excitation for short-time impedance spectroscopy

• Published in: Physiological measurement Vol. 29; no. 6; pp. S185 - S192
• Main Authors: Min, M, Pliquett, U, Nacke, T, Barthel, A, Annus, P, Land, R
• Format: Journal Article
• Language: English
• Published: England IOP Publishing 01.06.2008
• Subjects: Electric Impedance; Microfluidics; Spectrum Analysis - methods; Time Factors
• ISSN: 0967-3334; 1361-6579
• DOI: 10.1088/0967-3334/29/6/S16

Frequency domain impedance measurements are still the common approach in assessing passive electrical properties of cells and tissues. However, due to the time requirements for sweeping over a frequency range for performing spectroscopy, they are not suited for recovering fast impedance changes of biological objects. The use of broad bandwidth excitation and monitoring the response as a function of time will greatly reduce the measurement time. The widespread usage of a square wave excitation is simple but not always the best choice. Here we consider different waveforms for excitation and discuss not only the advantages but also their limitations. Measurements in a miniaturized chamber where frequency and time domain measurements are compared show the suitability of different waveforms as excitation signals for the measurements of bio-impedance. The chirp excitation has been found to be most promising in terms of frequency range, signal-to-noise ratio and crest factor.