Impedance bridges: from Wheatstone to Josephson

Abstract

This paper reviews the recent evolution of the measurement techniques in the area of impedance measurement from the Wheatstone bridge to the most advanced Josephson based digital impedance bridge. The progress in the development of high sampling rate, high accuracy digitaltoanalog and analogtodigital converters has led to the development of digital impedance bridges that have profoundly modified the landscape of impedance metrology. Although these new bridges do not yet outperform the traditional transformer based bridge in terms of accuracy, they significantly improve their measurement capabilities and flexibility by allowing a complete automation, a full coverage of the complex plane, arbitrary bridge ratios and extended frequency range. In addition, after the redefinition of the International System of Unit, they will contribute to the realization of the henry and the farad by establishing a direct link between the quantized Hall resistance and the capacitance or inductance standards.

From μ 0 to e: A Survey of Major Impacts for Electrical Measurements in Recent SI Revision

“…[23]- [26]. The SI value of the ohm was achieved by comparing the resistance value to the capacitance value through the quadrature bridge [27], [28]. The quadrature bridge employs two impedance branches (R 1 , R 2 and C 1 , C 2 ) and measures…”

Practical Precision Electrical Impedance Measurement for the 21st Century – EMPIR Project 17RPT04 VersICal

“…The accurate measurement of electrical impedance presents many challenges, not least the difficulty in defining the measured quantity. In the 150 years since the necessity to measure impedance arose in the field of telegraphy, many ingenious measuring techniques of ever-increasing accuracy have been developed [4,5]. Almost from the beginning, bridge methods were the favoured approach to the measurement of impedance and impedance ratio.…”

The Elementary Charge for the Definition and Realization of the Ampere

“…In contrast to traditional coaxial bridges, these instruments can measure impedance over the whole complex plane and continuously in frequency. The most advanced digital bridge at present is the dual Josephson impedance bridge based on two JAWS (see Section ) …”