Dielectric measurements using novel three-electrode technique

The polarization impedance at electrode surfaces can be particularly troublesome when dielectric measurements on high-conductivity fluids or semi-solids, including biological tissues, are attempted. For much biological work, where surface-penetrating measurements are required, relatively rugged dielectric probes are necessary. In such applications, electrode distance-variation or other compensation is too time-consuming. A highly practical solution to the problem uses three electrodes of non-equal areas but well-defined geometries. For use as an rugged, surface-penetrating probe, these can take the form of concentric cylindrical arrays of stout wires. Such a probe can be readily interfaced to commercially-available impedance analysers. By means of a reversal connection between the electrodes and the analyser, polarization-compensated measurements may be obtained over the frequency range 100 Hz-10 MHz.