Process Impedance Spectroscopy through Chirp Waveform Excitation

M. Nahvi and B. S. Hoyle

Institute of Integrated Information Systems, School of Electronic and Electrical Engineering University of Leeds, UK, Email: {eenmn, B.S.Hoyle}@leeds.ac.uk

ABSTRACT

The paper presents a new excitation method for electrical impedance spectroscopy in industrial processes. Electrical spectroscopy is potentially able to discriminate between different materials in a process. The method makes use of a chirp, in contrast to the conventional sinusoidal waveform used in tomographic process tomography. This has the advantage that a wide bandwidth of interest can be stimulated using a defined-parameter chirp excitation. The requisite parameter values from the measured waveform are extracted through an algorithm based on the wavelet transform that is described in the paper. The technique is illustrated using a process impedance simulation model consisting of a RC network. The paper provides a comparison between simulation and analytical solutions that demonstrate promise for a basic method that uses a four electrode technique to characterise different process materials (and possibly clinical tissue) and is capable of being scaled-up for use in multi-electrode electrical impedance spectro-tomography system.

Keywords Process spectroscopy, Electrical spectroscopy, Wavelet transform, Chirp waveform