The decreasing of the influence of parasitic inductance of tested object on the accuracy of its electrical capacitance measurement

This paper gives a description of measurement technique which can be used in practice of carrying out estimation of electrical capacitance of tested object with substantial stray inductance. Electrical capacitance is determined as a ratio of mean value of discharge current to the mean value of time derivative, taken from voltage on unknown capacitance. The decreasing of deleterious impact of stray inductance on accuracy of measurements is achieved by proper selection of the duration of analyzed signals. In proposed technique the duration is limited by instants of time that correspond to the maximum value of discharge current and to the termination of transient. The accuracy of described method for electrical capacitance estimation is affected by noisy components of obtained oscillograms. This deleterious impact can be alleviated by smoothing of time dependence by applying of least square method. Another reason for lost of accuracy is associated with possible influence of skin-effect in conductive elements of discharge circuit, which can cause time dependence of resistance and inner inductance of  conductive parts of tested object and discharge circuit. Described technique, however, is based on taking into consideration independent on time parameters of equivalent lamped discharge circuit. Nevertheless, the example of practical implementation has shown that described approach allows to partially mitigate the influence of stray inductance on carried out measurements of electrical capacitance, as the value of relative error turned out to be equal to 2.04%