The Study of a 2D Model for Dual Mode Excitation Electrical Impedance Tomography

Z. Cao1, H. Wang1, S. Liu2

1School of Electrical Engineering and Automation, Tianjin University, Tianjin, 300072, China.

2North China Electric Power University, Beijing 102206, China Email: zh_cao@tju.edu.cn, hxwang@tju.edu.cn

ABSTRACT

The task of electrical impedance tomography (EIT) is to recover information about cross-sectional material distribution in the form of reconstructed images by using electrical measurements on the boundary of the interested region. It has several advantages over other tomographic techniques, e.g. low-cost, rapid response, portability, non-invasion and robustness. However, it is not easy to extract impedance information simultaneously over the same cross section. In the literature, researchers proposed mainly a strategy based on a combination of ERT and ECT sensors alternatively over the same cross-section of the interested area, and in this design, the information of resistance and capacitance is obtained sequentially, since the ERT sensor and ECT sensor are used sequentially. This means that impedance information is extracted in a time-sharing method, at the risk of either hardware complexity or information fusion difficulty, because each mode operates in its own way and is limited to resistive or capacitive measurement range only. In this paper, a 2D model has been established to obtain impedance information of resistive as well as capacitive modes simultaneously. Based on the model, the measurement can be performed in either two-port measurement strategy or four-port measurement strategy. Meanwhile, the sensor described in the model is self-calibrated. Thus it can be used to a variety of industry fields and is not just limited to the tomography techniques. Based on the model, the sensor can be designed in other shapes, such as a rectangle, triangle, etc, using the conformal transformation. Images are constructed using Tikhonov regularization based on the sensitivity theorem.

Keywords 2D model, dual mode, impedance sensor, conformal transformation