Comparison of the Josephson voltage standards of the NMC, A*STAR and the BIPM (part of the ongoing BIPM key comparisons BIPM.EM-K10.a and BIPM.EM-K10.b)

Solve, S; Chayramy, R; Stöck, M; Zhou, Yi; Lee, Jinni; Chua, S.W.

doi:10.1088/0026-1394/48/1a/01006

Cited by 3 publications

(5 citation statements)

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“…We measured the resistance leakage to ground of a single PJVS system using a measurement setup (figure 7) previously developed and proven at BIPM [22,23]. A resistance r of 1 k is connected from one side of the array to the ground.…”

Section: Leakage Resistance Measurement Setupmentioning

confidence: 99%

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Direct comparison of two NIST PJVS systems at 10 V

et al. 2013

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Two NIST programmable Josephson voltage standard (PJVS) systems are directly compared at 10 V using different nanovoltmeters. These PJVS systems use arrays of triple-stacked superconducting niobium Josephson junctions with barriers made of niobium silicide. Compared with the voltages produced by Josephson voltage standards based on hysteretic junctions, PJVS systems using damped junctions produce predictable voltage levels. However, in order to guarantee the quantization of the voltages and to minimize the errors at the room-temperature voltage output, additional precautions are required. We report several experimental results of voltage measurements that contain significant systematic errors. The generated voltages appear reproducible but they are, in fact, inaccurate. When proper measurement procedures are followed, the results of a direct comparison using an analogue detector show that the two independent PJVS systems agree within 2.6 parts in 1011 at 10 V with a relative total combined uncertainty of 3.4 parts in 1011 (k = 1). Investigations show that the largest systematic error and most significant contribution to the uncertainty budget is caused by the leakage resistance of each PJVS to ground. This paper describes a measurement procedure to characterize this leakage resistance and one approach to including the resulting voltage error in the uncertainty budget.

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Section: Leakage Resistance Measurement Setupmentioning

confidence: 99%

“…In the worst case, the systematic error, e, is of the order of a few nanovolts and will lead to a detectable systematic error in the comparison measurements [22]. The bias current source and power supply LRGs of a PJVS will, by definition, always contribute to the LRG error.…”

Section: Introductionmentioning

confidence: 99%

Direct comparison of two NIST PJVS systems at 10 V

et al. 2013

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“…Analog NVMs can provide a factor of two improvement in measurement noise over that of the best digital null detectors [18,19]. Analog null detectors are routinely used by BIPM in option A of the protocol of BIPM.EM-K10 key comparison framework [20]. Another type of NVM [21] has also been developed for such application but was not evaluated in this study.…”

Section: Comparison Measurement Setup and Synchronizationmentioning

confidence: 99%

“…of the overload voltage and duration. To avoid overloads, all previously reported NVM voltage standard comparisons were performed manually [20], and a protection circuit was required at the input to the NVM that was engaged at each PJVS polarity reversal. We avoid overloads with an innovative approach that simultaneously reverses the polarity of both PJVS arrays such that the magnitude of the voltage at the NVM input remains within the selected 10 µV range.…”

Section: Comparison Measurement Setup and Synchronizationmentioning

confidence: 99%

Automated direct comparison of two cryocooled 10 volt programmable Josephson voltage standards

et al. 2018

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We have performed direct dc comparisons between two cryocooled 10 V programmable Josephson voltage standards. Utilizing an automated synchronization scheme for the voltage reversals enables use of a high-sensitivity analog null detector on its 10 µV range. No switches or manual operations are necessary to protect the null detector from overload signals. The agreement measured between the two voltage standards at 10 V is 9 parts in 1012 with a relative combined uncertainty of 29 pV V−1 (k = 2 coverage factor). Since both systems can be operated floating from ground, various grounding configurations of the measurement circuit were investigated to evaluate possible leakage current paths to ground. Comparing the two systems under various grounding conditions enables minimization of leakage-current errors, optimization of system performance by revealing leakage-limiting components, and verification of key elements in the uncertainty budget for the measurement method.

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“…If the array is connected to an 'isolation ground' in the bias supply, this point must not be inadvertently connected to ground where it can add a significant systematic error [17,18]. To reduce the coupling effects between both standards, it has been demonstrated that biasing two arrays with only one dc bias source (the array to be compared naturally goes to within a few steps of the voltage provided by the reference array) provides a useful method of determining errors originating from ground loops [19].…”

Section: Ground Loopsmentioning

confidence: 99%

BIPM direct on-site Josephson voltage standard comparisons: 20 years of results

Solve¹,

Stöck²

2012

Meas. Sci. Technol.

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The discovery of the Josephson effect has for the first time given national metrology institutes (NMIs) the possibility of maintaining voltage references which are stable in time. In addition, the introduction in 1990 of a conventional value for the Josephson constant, KJ-90, has greatly improved world-wide consistency among representations of the volt. For 20 years, the Bureau International des Poids et Mesures (BIPM) has conducted an ongoing, direct, on-site key comparison of Josephson voltage standards among NMIs under the denominations BIPM.EM-K10.a (1 V) and BIPM.EM-K10.b (10 V) in the framework of the mutual recognition arrangement (CIPM MRA). The results of 41 comparisons illustrate the consistency among primary voltage standards and have demonstrated that a relative total uncertainty of a few parts in 1010 is achievable if a few precautions are taken with regard to the measurement set-up. Of particular importance are the grounding, efficient filters and high insulation resistance of the measurement leads, and clean microwave distribution along the propagation line to the Josephson array. This paper reviews the comparison scheme and technical issues that need to be taken into account to achieve a relative uncertainty at the level of a few parts in 1010 or even a few parts in 1011 in the best cases.

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Comparison of the Josephson voltage standards of the NMC, A*STAR and the BIPM (part of the ongoing BIPM key comparisons BIPM.EM-K10.a and BIPM.EM-K10.b)

Cited by 3 publications

References 1 publication

Direct comparison of two NIST PJVS systems at 10 V

Direct comparison of two NIST PJVS systems at 10 V

Automated direct comparison of two cryocooled 10 volt programmable Josephson voltage standards

BIPM direct on-site Josephson voltage standard comparisons: 20 years of results

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