Methods and equipment for measuring precisely the temperature coefficient of capacitance

Abstract

1. The static method for measuring the temperature coefficients of capacitance is the most reliable and precise. The application of quadratic formulas in approximating the capacitors' temperature curves used over a wide temperature range increases substantially the precision in evaluating temperature coefficients by means of the static method. 2. The dynamic method for measuring the temperature coefficient of capacitance is more rapid and practical than the static method, and it does not require interpolation of intermediate points. However, the error sources of this method have not been fully investigated. 3. For obtaining a maximum sensitivity to capacitance variations in instruments used for measuring the temperature coefficient of capacitance it is necessary to use additional devices (reference oscillators, auxiliary branches, differential circuits), and for reducing the error special methods should be used (substitution, bracket-method readings). 4. The best instruments for measuring the temperature coefficient of capacitance are based on three-terminal ac bridge circuits. These instruments can be provided with a minimum measurement error amounting to ±(0.005η+0.5·10−6) deg−1. They measure the temperature coefficients of the true capacitance and of the loss-angle tangent, whereas other instruments measure only the temperature coefficient of the capacitors' effective values.