The Measurement of Capacitance in Terms of Resistance and Frequency

The adaptation of a bridge circuit due to M. Wien together with apparatus and procedure is described which permits measurement of capacitance in terms of resistance and frequency with an accuracy comparable to that of the primary standards. Among its advantages over the Maxwell method commonly employed are the use of a single frequency voltage and the fact that there is no general limitation placed on the type of condenser which may be measured or on the frequency at which the measurement may be made. The method is also applicable to the determination of inductance since its unit, like that of capacitance, may be derived from the units of resistance and frequency. INTRODUCTION C O N D E N S E R S are commonly measured by comparison with standard condensers of known value by means of one or another of the well-known bridge methods. The accuracy with which such measurements can be made depends upon the accuracy with which the capacitance of the standard is known. The unit of capacitance is derivable from those of resistance and frequency and to obtain an absolute value for a standard of capacitance, some method is required for a precise determination of capacitance in terms of frequency and resistance. Of the methods which have been proposed, few yield the accuracy with which the primary standards of resistance and frequency are known and reproducible. A generally accepted method for the absolute determination of capacitance in terms of resistance and frequency is to use a bridge, due to Maxwell,1 employing the alternate charge and discharge of a condenser.