The voltage coefficients of precision capacitors

A method is presented for the measurement of the variation of capacitance with voltage in gas-dielectric capacitors. It consists of applying to the capacitor a direct voltage and using a small alternating voltage to measure the capacitance variation. The direct voltage coefficient obtained in this manner differs from that obtained with alternating voltage, and this relationship is studied theoretically and verified experimentally. High-voltage compressed gas capacitors can have appreciable voltage coefficients because of eccentricity in their electrode structure. A method is presented for detecting and correcting such eccentricity without opening the capacitor. The voltage coefficients of a few solid dielectric capacitors were measured by comparison with a known air-dielectric capacitor and the results reported.