Experiences with a two terminal-pair digital impedance bridge

Describes the realization and preliminary tests of a two terminal-pair digital impedance bridge. The bridge, with a very simple architecture, is based on a commercial two-channel digital signal synthesizer, and a synchronous detector. The bridge can perform comparisons between impedances having arbitrary phase and magnitude ratio: its balance is achieved automatically in less than a minute. R-C comparisons with calibrated standard, at kHz frequency and 100 kΩ magnitude level, give ratio errors of the order of 10
^-5
, with potential for further improvements.