A Self-Oscillatory Converter of Parameters
of a Capacitive Sensor with High Losses

G. P. Eroshenko, V. P. Parusov, and V. N. Sharuev

Vavilov State Agrarian University, Teatral’naya pl. 1, Saratov, 410710 Russia

Received June 6, 2000

Abstract—The converter is designed on the basis of a field-effect transistor with a balanced thermistor bridge
connected to the drain circuit. The output of this thermistor bridge is connected to the transistor gate through a
circuit specifying the operating frequency. The sensor is connected in parallel to the thermistor. The initial con-
version frequency is 1 MHz, the range of measured capacitances is 5 10^–2–10^–3 pF, and the error in the sepa-
rability of converted parameters does not exceed 2% for conductances ranging from 0 to 2 10^–2 S.

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