Experiences with a two terminal-pair digital impedance bridge

TL;DR

This paper presents a simple, automated digital impedance bridge capable of precise impedance comparisons across arbitrary phase and magnitude ratios, demonstrating high accuracy in $R$-$C$ measurements at kHz frequencies.

Contribution

The paper introduces a novel, simple architecture for a digital impedance bridge utilizing commercial components, enabling rapid and accurate impedance comparisons with minimal setup.

Findings

Achieved ratio errors of about 10^-6 in $R$-$C$ comparisons

Automatic balancing in less than a minute

Potential for further accuracy improvements

Abstract

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 impedances having arbitrary phase and magnitude ratio: its balance is achieved automatically in less than a minute. $R$-$C$ comparisons with calibrated standards, at kHz frequency and 100 kohm magnitude level, give ratio errors of the order of $10^{-6}$, with potential for further improvements.