Wideband electrical impedance tomography

Abstract

This paper addresses the augmentation of a conventional single frequency electrical impedance tomography (EIT) system to form a wideband EIT system. This extends the system to provide spectral information, but with the essential capability to match process dynamics. The underlying opportunity for this study is that process materials may show considerable change in their electrical properties in response to an injected signal over a wide frequency range. This concept is used in the paper to demonstrate the construction of tomographic images for a range of frequency bands that can provide a deeper understanding and interpretation of a process under investigation. This paper describes a trial simulation of this approach and an experimental study. To provide measurements over the required frequency range a linear chirp is used as the excitation signal. Corresponding peripheral measurements have been synthesized using a 2D model in association with the EIDORS forward solver. The measurements are then analysed using an algorithm based on the wavelet transform to reveal spectral band datasets. In the presented feasibility trial a single-channel EIT chirp excitation was implemented, in essence simulating a real-time parallel data collection system, through the use of pseudo-static tests on foodstuff materials. The experimental data were then analysed and tomographic images were reconstructed using the frequency-banded data. The qualitative feasibility results illustrate the promise of this composite approach in exploiting sensitivity to variations over a wide frequency range. They indicate that the described method can augment an EIT sensing procedure to support spectroscopic analysis of the process materials.