A Novel Multi-electrode Sensing Strategy for Electrical Capacitance Tomography with Ultra-low Dynamic Range

Common sensing strategy of Electrical Capacitance Tomography (ECT) is to measure the capacitances across all independent combinations of individual electrodes. The capacitance values from common sensing strategies usually have a large dynamic range and suffer nonlinear effect in image reconstruction procedure when using linearized ECT model, thus making it difficult to obtain satisfactory images. In this paper, a novel multi-electrode sensing strategy for ECT is reported to offer improved solutions regarding these problems. The proposed sensing strategy takes advantage of the flexibility of combining electrode method, while a new opposite multi-electrode asymmetric excitation and measurement protocol is further developed. A 24-electrode ECT sensor is selected as the basic sensor, and a pair of asymmetrically opposite electrodes are excited in a simultaneous manner. The proposed sensing strategy can significantly decrease the dynamic range of measurements. Moreover, the nonlinear effect is weaker compared with that of typical sensing strategy when performing linearized-model-based image reconstruction. To validate the proposed strategy, modelling of 3D ECT sensors and numerical analysis are carried out. The proposed strategy is characterized from the aspects of capacitance measurement, compression ratio, dynamic range, sensitivity map, and quality of reconstructions. Additionally, experimental validation is also conducted. Both simulation and experiment results indicate significantly improved sensing characteristics and quality of reconstructed images. This novel sensing strategy will lead to a lower burden for capacitance measurement circuit and better quality of tomographic image.