A novel sensing strategy for electrical capacitance tomography

Common measurement strategy in Electrical Capacitance Tomography (ECT) is to sense capacitance across all independent combinations of individual electrodes (usually 12 electrodes). These capacitance values usually have a large dynamic range and suffer severe nonlinear effect in reconstructions when using a linearized model, which makes it difficult to obtain high quality images. In this paper, a novel sensing strategy for ECT is reported to overcome such problems. The proposed strategy takes advantage of the flexibility of combining electrode strategy, while an opposite multi-electrode asymmetric excitation (MeAE) measurement protocol is further developed. A 24-electrode ECT sensor is designed as the basic sensor, and a pair of asymmetrically opposite electrodes are excited in a simultaneous manner. The proposed strategy can significantly decrease the dynamic range of measurements. Moreover, the nonlinear effect of the linear model based on the proposed strategy is weaker compared with that utilizing all electrode combinations. To validate the proposed strategy, a 3D ECT sensor was modelled and numerical analysis was carried out. The strategy was evaluated from the aspects of capacitance measurements, dynamic range, sensitivity characterization, and quality of reconstructed image. The simulation study results indicate that compared with traditional 12-electrode ECT measurement strategy, dynamic range of the proposed strategy is decreased by around 6.7 times, and most importantly, only three kinds of electrode combinations are employed on the premise of preserving enough information for image reconstruction. Meanwhile, quality of reconstructed images is also improved for different test phantoms. This novel sensing strategy will lead to lower demand for ECT hardware development and better quality of tomographic image.