New Multi-Frequency Method for the Determination of the Dissipation Factor of Capacitors and of the Time Constant of Resistors

A new method for the simultaneous determination of the dissipation factor of capacitors and of the time constant of resistors by a multi-frequency method is presented. This method is based on the measurement of impedance ratios at two or more frequencies. A bridge is set up with a programmable two-channel ac voltage source and the impedances to be compared. The impedance ratios are determined by synchronous sampling procedures and application of discrete Fourier transform. In a first experiment, a high-grade gas-filled 1-nF standard capacitor was compared with a stable 1-MOmega ac resistor at frequencies between 40 Hz and 660 Hz. The estimated standard uncertainties (k = 1) are 0.7 times 10^-6 for the dissipation factor of the capacitor and 0.6 ns for the time constant of the ac resistor