Four-terminal scheme used in a two-terminal EIT system

In this paper, mutual conversions were implemented between the two-terminal and four-terminal schemes, which would bring convenience of measurement for the EIT, while not affecting the image quality. A portable two-terminal EIT system based on AD5933 was designed. This system, under the control of a PC via the USB interface, could sweep frequency to achieve a high precision in impedance measurement by means of impedance spectroscopy. Simulation results verified that the conversion formula worked and showed that the effect of image reconstruction using a four-terminal measurement scheme was better than using a two-terminal measurement scheme. Experimental results will be given later.