Using Eddy Current Measuring System for Conductivity Based Gas Sensor

Methods of contactless measurements of electrical quantities represent generally an efficient way of avoiding measurement uncertainties and constructional problems caused by complicated phenomena occurring on the interface electrode electrolyte or electrode-semiconductor. Measurement of electromagnetic field generated by eddy-currents in conductive object is very often used for evaluation of object properties i.e., for diagnostic purposes. The same principle is theoretically applicable for measurement of electrical conductivity of the surface layer in semiconductor based gas concentration sensors. The aim of this article is to prove experimentally feasibility of eddy current methods for conductivity measurement of gas concentration sensors. On the basis of simplified electrical circuit model the optimization of measuring systems parameters is performed and the results of concentration measurement of H-2 and NO2 on laboratory prototype of gas sensor are introduced. Introductory experiments performed on sensor prototype using sophisticated impedance analyzer could serve for further development of the electrode-less semiconductor gas concentration sensors using simple impedance convertor in form of integrated circuit.