Experiences With a Two-Terminal-Pair Digital Impedance Bridge

This paper describes the realization of a two-terminal-pair digital impedance bridge and the test measurements performed with it. 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 the impedances having arbitrary phase and magnitude ratio. The bridge balance is achieved automatically in less than 1 min. R-C comparisons with calibrated standards, at kilohertz frequencies and 100-kQ magnitude level, give ratio errors of the order of 10^-6, with potential for further improvements.