Complex admittance measurements in ECT for conductivity and permittivity imaging: a theoretical evaluation

A novel reconstruction method for electrical capacitance tomography is presented in this paper, where both the permittivity and the conductivity distribution of dielectric materials are considered. In order to clarify how the conductivity of background medium affects the quality of reconstructed results, detailed analysis of the relationship between the conductivity/frequency and the capacitance measurements based on complex admittance measurements are carried out. Consequently, it is found that theoretically if we can operate in higher frequency and with complex admittance measurement it may help to generate better images of both real and imaginary distribution of permittivity at the same level of conductivity. This will be especially important for the higher value of conductivity background where currently ECT fails to work. Simulations studies in this work are carried out with complex ECT electrodes are outside of an insulating pipe, and hence a truly capacitive coupled complex permittivity imaging including dielectric permittivity and electrical conductivity.