Sensor Design for Four-Electrode Electrical Resistance Tomography With Voltage Excitation

Electrical resistance tomography (ERT) is used to image conductivity distributions. Most existing ERT systems are based on a current-excitation and voltage-detection to measure resistance with the use of small pin electrodes. This measurement technique has several limitations, like the existence of a severe fringe effect. This generates image distortion and no quantitative data can be acquired. In addition, the conventional ERT systems are not able to image stratified flows. The ERT systems using voltage-excitation and current-detection (VECD) with large rectangular electrodes were proposed, overcoming the limitations of conventional ERT. The VECD technique can reduce image distortion due to smaller fringe effect and allows imaging stratified flows. In the past, the two-electrode sensing technique was used without careful consideration of parasitic resistance, as the contact impedance. This paper presents a design of ERT with voltage excitation with a four-electrode sensor structure to reduce the effect of the contact impedance, the resistance of the switching stage, and the wiring on the internal resistance measurement. The simulation and experimental results with different conductivity distributions show the superior performance of the proposed structure.