A frequency selection scheme for increased imaging speed in ECT

Electrical capacitance tomography (ECT) is a method to determine the material distribution within the interior of a closed object by measuring the capacitance values across externally mounted electrodes. Traditionally, an ac excitation pulse is applied to a pair of electrodes that form a capacitor during each measurement step, in order to determine the capacitance from the output current measured. This paper investigates how the speed of inter-electrode capacitance measurement can be improved by applying and receiving multiple excitation signals simultaneously on multiple electrodes. An excitation frequency selection scheme is derived to discuss the effect of bandwidth on the interference between the simultaneously sampled measurement channels. The new scheme opens up new possibilities for ECT as an effective tool for online, real-time monitoring of a wide range of dynamical processes.