Impedance Matched Front-End Circuitry for Electrical Capacitance Tomography Systems

Electrical capacitance tomography (ECT) is a well-established technique for process monitoring. ECT is used to observe goods and process optimization in industrial applications. High temperatures or high pressures are common conditions in industrial environments. To dislocate the vulnerable ECT measurement electronics from the sensor, where such unfavourable conditions may prevail, long instrumentation lines are required. For increasing excitation frequencies, impedance transformation properties of those lines emerge. To overcome this undesired effect, we propose a front-end structure which meets the characteristic instrumentation line impedance. In this paper we present the analysis of a 50 Ω matched front-end design for electrical capacitance tomography. The transmitter stage as well as the receiver is analysed by means of simulations. The results are compared with a commonly used low-impedance structure. Further insights of the matched receiver structure are obtained by measurements, carried out with a realized prototype.