The main idea of the ECT technique is the production of an image of the cross-section
area within a process vessel on the basis of measurements taken on its outer boundaries e.g.
around the periphery of the process vessel or pipe [10, 16, 18] . The measured capacitances
are related to dielectric constant of investigated materials or their permittivity. The relationship
between capacitance on a pair of electrodes and permittivity is given by equation (1):