Electrical Resistance/Capacitance Dual-Mode Tomography Based on Dual-Frequency Response

Electrical capacitance tomography (ECT) and electrical resistance tomography (ERT) are promising techniques for multiphase flow imaging due to high-speed, low-cost, noninvasive, and visualization features. At present, ECT/ERT dual-mode imaging is generally accomplished by the combination of ECT and ERT sensors implemented through different electrode arrays, and with separate systems to collect the projection data, due to their different sensing principles. To expand different sensing ranges of ECT and ERT, a dual-mode tomography over a wide electrical sensing frequency band based on dual-frequency response is proposed in this article. A dual-frequency excitation/probing scheme is used to measure the capacitance and conductance of the fluid through one set of electrode arrays, to visualize the permittivity and conductivity distribution in the same pipe cross section. The frequency responses of different combinations of conductive, weakly conductive, and nonconductive substances were tested. Static and dynamic experimental tests were carried out. The experimental results in ECT and ERT are satisfactory, demonstrating the feasibility of the proposed ECT/ERT dual-mode technique.