A three-arm current comparator bridge, for impedance comparisons over the complex plane

TL;DR

This paper introduces a novel three-arm current comparator impedance bridge capable of comparing three different impedances with arbitrary phase angles, validated through measurements of inductors and RC networks at kHz frequencies.

Contribution

The paper presents the concept, analysis, and practical realization of a three-arm impedance bridge for complex impedance comparisons, expanding calibration capabilities.

Findings

Measurements agree with standards within 10^-5 to 10^-6 relative deviation

The bridge effectively compares complex impedances at kHz frequencies

Validation through air-core inductor and RC network tests

Abstract

We present here the concept of three-arm current comparator impedance bridge, which allows comparisons among three unlike impedances. Its purpose is the calibration of impedances having arbitrary phase angles, against calibrated nearly-pure impedances. An analysis of the bridge optimal setting and proper operation is presented. To test the concept, a two terminal-pair digitally-assisted bridge has been realized; measurements of an air-core inductor and of an RC network versus decade resistance and capacitance standards, at kHz frequency, have been performed. The bridge measurements are compatible with previous knowledge of the standards' values with relative deviations in the 10^-5 -- 10^-6 range.