Linearization Point and Frequency Selection for Complex-Valued Electrical Capacitance Tomography

Benefiting from the ability to image the permittivity distribution of dielectric materials, electrical capacitance tomography (ECT) has been applied for multiphase flow metering for decades as a contactless method. However, the water-continuous flow brings challenges for ECT since the conductivity in water makes ECT fail to reconstruct the distribution. Therefore, complex-valued ECT (CV-ECT) is introduced to image both permittivity and conductivity distribution based on complex-valued capacitance measurements using the same sensor head of ECT. Different from conventional ECT, the investigation of excitation frequency and linearization point selection is vital for CV-ECT, as the conductivity information is coupled with permittivity and frequency. An eight-electrode CV-ECT system was set up to obtain measurements both in simulations and experiments. The measurements on different phantoms over different excitation frequencies were conducted, and the images were reconstructed to elaborate the selection of the linearization point and excitation frequency range.