An international comparison of phase angle standards between the novel impedance bridges of CMI, INRIM and METAS

Abstract

We report here the results of a comparison of electrical impedance standards aimed at evaluating four novel digital impedance bridges developed by the national metrology institutes CMI, INRIM and METAS. This comparison, which is the first of its kind, involved phase angle impedance standards developed by TÜBİTAK UME with phase angles of ±30 • and ±60 • , and magnitudes ranging from about 100 Ω to 1 MΩ. The comparison demonstrated agreement among the measurement results obtained with the different bridges, and allowed us to gather information on the stability of the phase standards and on the more critical aspects related to the characterization of the bridges.

A Comprehensive Analysis of Error Sources in Electronic Fully Digital Impedance Bridges

“…where the term E k0 represents a possible residual voltage at the channel output, independent of the other channels settings, and a kj is the (complex) coupling coefficient from channel j to channel k. Substituting (11) into 3and 4, combining the forward and reverse errors with (6), and approximating at first order in the E k0 's and a kj 's yields…”

“…From the first designs of the 1980s [2]- [6], electronic fully-digital impedance bridges based on polyphase digital signal generators have emerged in recent years as measuring systems suitable for primary impedance metrology [1], [7]- [11]. With typical accuracies in the 10 −6 -10 −5 range, these kinds of bridges are not as accurate as traditional transformerratio bridges [10], [12], [13] or Josephson bridges [14]- [17], but can measure impedances across the whole complex plane and are characterized by affordable cost, short measuring time and ease of operation.…”

Primary Realization of Inductance and Capacitance Scales With a Fully Digital Bridge

“…and capacitance scales. In particular, electronic fully-digital impedance bridges [15]- [17], [21]- [23], [25], [26] do not include calibrated ratio transformers in their implementation but rely on the accuracy of the electronic waveform synthesizers employed. These can be more easily manufactured and operated, thus allowing developing metrology institutes and calibration centers to realize impedance scales.…”

“…Moreover, the implementation is expensive with a suboptimal level of automation. More recently, INRIM was involved in the development of fullydigital bridges [16], [23], [25], [26] in the framework of a number of European joint research projects [31]- [36]. In particular, the project VersICaL 1 had the specific objective of developing a new fully-digital bridge to be used as a primary reference bridge for the realization of impedance units and scales in national metrology institutes and calibration centers, and for the training of electrical metrologists [37].…”

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

“…The research builds on the outcome of a previous joint research project "Automated impedance metrology extending the quantum toolbox for electricity" (AIM QuTE) which demonstrated, among other outcomes, that digital impedance bridges have the capacity to rival traditional bridges based on transformer ratios [3]. These novel bridges have the advantages of being economic to build, easy to operate and readily configurable to measure impedances with arbitrary phase angles.…”