Dual Josephson impedance bridge: towards a universal bridge for impedance metrology

Abstract

This paper presents a full characterization of a Dual Josephson Impedance Bridge (DJIB) at frequencies up to 80 kHz by using the DJIB to compare the best available impedance standards that are (a) directly traceable to the quantum Hall effect, (b) used as part of international impedance comparisons, or (c) believed to have calculable frequency dependence. The heart of the system is a dual Josephson Arbitrary Waveform Synthesizer (JAWS) source that offers unprecedented flexibility in high-precision impedance measurements. The JAWS sources allow a single bridge to compare impedances with arbitrary ratios and phase angles in the complex plane. The uncertainty budget shows that both the traditional METAS bridges and the DJIB have comparable uncertainties in the kilohertz range. This shows that the advantages of the DJIB, including the flexibility which allows the comparison of arbitrary impedances, the wide frequency range, and the automated balancing procedure, are obtained without compromising the measurement uncertainties. These results demonstrate that this type of instrument can considerably simplify the realization and maintenance of the various impedance scales. In addition, the DJIB is a very sensitive tool for investigating the frequency-dependent systematic-errors that can occur in impedance construction and in the voltage provided by the JAWS source at frequencies greater than 10 kHz.

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

“…To cancel the effect of the synthesizer's gain error, the reading is obtained from two successive balances: in the forward configuration, the bridge is balanced as in figure 1; in the reverse configuration, the bridge is balanced with the channels E 1 and E 2 exchanged at the ports HS1 and HS2. The bridge reading is then computed as [16], [24], [26]…”

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

“…The square root of (2), with complex argument, should be determined so that the phase of W read agrees with that of W (or with that of either W read F or W read R ). Alternatively, following [17], equation (2) can be rewritten as…”

“…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. These features make them suitable for smaller national metrology institutes and calibration laboratories.…”

“…In particular, this work aims at collecting and expanding in a unified and general way some of the results that are scattered throughout the literature on fully-digital impedance bridges (e.g. [8], [17], [18]). A short summary was presented in [19].…”

Mutual validation of PTB’s Josephson and INRIM-POLITO’s electronic impedance bridges for the realization of the farad from graphene quantum standards

“…A further alternative can be a special type of digital impedance bridge, which exploits two pulse-driven Josephson junction arrays (also called Josephson Arbitrary Waveform Synthesizer, JAWS) to provide arbitrary voltage ratios with an arbitrary phase angle. By providing quantum based AC signals with high accuracy and extremely low harmonic content [8], the JAWS can efficiently be adopted for impedance metrol-ogy [9].…”