Digital generator assisted impedance bridge

A prototype wide-range four-terminal-pair universal impedance bridge has been constructed in order to test ideas for balancing procedures and noise performance. The relative standard uncertainty (1sigma) contributed by noise and short-term drift to the measurement of resistance, capacitance, and inductance is less than 10 X 10(-6) from 1 to 30 kHz, and less than 35 x 10(-6) at 100 kHz. A two-phase digital voltage generator provides the two voltages required to bring the bridge to near, but not exact, balance. The detector offset voltages are measured with a vector voltmeter and used to correct for the inexact balance.