Ckd Praha, Oborovy Podnik

Milos Jurca

A rapid and accurate technique for generating indications representative of the specific resistance of a test sample, such as a silicon disc, is described. A capacitive probe is electrostatically coupled to the sample, and the input terminals of the probe are coupled to the output terminals of a reactive circuit that is excited with a high-frequency current and that includes a capacitive path connected across an input coil to transform the measured loss resistance of the sample (proportional to the specific resistance) to the terminals of the first coil. An auxiliary path including a pair of serially connected compensating inductors is connected between the junction of the capacitors in the capacitive path and a reference terminal of the input coil, with the junction of the compensating coils and the reference terminal forming the output of the reactive circuit. When the compensating inductances are individually adjusted to resonate with the coupling capacitance between the probe and the test sample and with the probe capacitance, respectively, at the frequency of excitation of the reactive circuit, the change in voltage across the capacitive path when the probe is connected to the output of the reactive circuit varies as a function of the specific resistance of the sample.

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Prague, Czechia

Milos Jurca