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A new method for the simultaneous determination of the dissipation factor of capacitors and of the time constant of resistors by a multifrequency 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 MΩ ac resistor at frequencies between 31 Hz and 666 Hz. The estimated standard uncertainties (k=1) are 0.6·10-6 for the dissipation factor of the capacitor and 0.4 ns for the time constant of the ac resistor.