Techniques for semi-empirical characterization of material and sensor properties in interdigital dielectrometry

Interdigital frequency-wavenumber dielectrometry can be used for measurement of dielectric properties of insulating materials. It is not always possible to adequately model distributed circuit parameters of the sensor structure. Even in cases when the forward problem can be solved, that is, the distribution of electric field can be calculated using numerical techniques, it may not be suitable for the solution of the inverse problem due to the high sensitivity of the parameter estimation algorithms to variations in circuit and material parameters as well as nonideality in the models due to finite size of the sensor, fringing field effects, and lead effects. This paper particularly shows the advantage of changing the function of the conducting plane beneath the interdigital electrode structure from a ground plane to a guard electrode that follows the sensing electrode voltage. The techniques presented in this paper build a bridge between idealized models of interdigital structures and real measurements. Employment of such techniques allows experimental calibration of the sensor, verification of the intermediate steps in the process of development of parameter estimation algorithms, and provide data necessary for improvement of experimental arrangements.