R Chayramy

Direct comparison between a programmable and a conventional Josephson voltage standard at the level of 10?V

A Josephson voltage standard (JVS) from the BIPM, incorporating a PTB 10 V programmable array, has been compared with a JVS from the LNE, operating with a conventional hysteretic array. The metrological characteristics of both JVSs were carefully studied. We report on the experiments performed for this comparison and on the uncertainty components. The final comparison result is (UPJVS − UJVS)/UJVS = −3.2 × 10−11 with a relative total combined standard uncertainty of 6.1 × 10−11 (k = 1).

The BIPM compact Josephson voltage standard

The BIPM has developed a new Josephson Voltage Standard (JVS) that will replace the present transportable standard in the near future. The old system has been involved in 17 international comparisons at the level of 10 V in the framework of the BIPM direct on-site JVS key comparison since 1994. The heart of the new primary standard will still consist of arrays of SIS junctions. It will be able to use future 10 V programmable arrays with minor modifications. We present here the technical details of the key parts of the compact primary JVS. The preliminary results of a direct comparison against the current BIPM 10 V primary reference have shown an agreement within a total combined relative uncertainty of 1×10−10 (k = 1).

The BIPM Compact Josephson Voltage Standard

Fifteen National Metrology Institutes have recently confirmed their interest in participating in the International Bureau of Weights and Measures (BIPM) direct on-site comparison of Josephson array voltage standards at the level of 10 V. This comparison has been ongoing since 1994, and the BIPM primary standard involved needs to be replaced by a new standard built from components based on modern technology. We present here in detail the components of the new BIPM Josephson voltage standard. The main goal during its development was to realize a standard that is more easily transportable, more convenient to use, and as efficient and reliable as its predecessor. Both primary standards have already shown agreement within a total combined relative uncertainty of 1.4 × 10-10 (k = 1).

Direct 10 V Josephson Voltage Standard comparison between a programmable sinis array and a conventional sis array

In December 2007, a comparison of the 10 V Josephson Array Voltage Standard (JAVS) of the LNE was performed with that of the BIPM in the framework of BIPM.EM-KlO.b comparison. During the week allotted to the exercise, the measurement setup was optimized to achieve a relative voltage difference of 7times10-12 within a relative Type A uncertainty of 8times10-12. We then took the opportunity to carry out a direct comparison of a 10 V PTB programmable array against the LNE JAVS. We report on the experiments performed to establish the uncertainty budget. We present the characterization of a 10 V SINIS array. We conclude with the results of a direct comparison against the LNE JAVS.

A New Fully Automated Measurement Chain for Electronic Voltage Standards at 1.018 V

The authors describe a new automated measurement system for the direct calibration of the 1.018-V outputs of Zener-based electronic voltage standards with a programmable Josephson array. It features a programmable bias supply and a multiplexer that introduces negligibly small thermal EMFs in the critical circuits. Detailed descriptions of the two devices are given in this paper. A validation program is in progress in parallel with the previous chain, as no instruments are shared between the two

The leakage resistance to ground of a NIST Programmable Josephson Voltage Standard

The Programmable Josephson Voltage Standard (PJVS) leakage resistance to ground (LRG) is defined as the electrical resistance of one side of the measurement leads to ground. Under certain measurement conditions, this resistance can produce a significant systematic voltage error of the measured value of the PJVS output voltage. In particular, if the low side of the array is grounded, for instance in a direct comparison measurement with another JVS, then the LRG will reduce the PJVS output voltage. At 10 V, an error of 0.5 nV can result from a LRG of 50 GΩ if the measurement leads have a total resistance of 2.5 Ω. The LRG and the path of the leakage current to ground are difficult to determine. Furthermore, its corresponding voltage error is still present while the bias source is in operation to control the PJVS. It is therefore important to apply different measurement techniques to compare the corresponding LRG values.

Comparison of the Josephson voltage standards of the EIM and the BIPM

A comparison of the 10 V Josephson array voltage standard of the Bureau International des Poids et Mesures (BIPM) was made with that of the Hellenic Institute of Metrology (EIM), Greece, in March 2010. For this exercise, the option B of the BIPM.EM-K10.b comparison protocol was applied, in which the BIPM only provides a reference voltage that has to be measured by the EIM using its Josephson voltage standard and its own measuring device. The results of the two participants are in very good agreement and the overall relative standard uncertainty is 2.0 parts in 1010. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

A Bias Source for the Voltage Reference of the BIPM Watt Balance

We have developed a programmable current bias source to set the voltage output of a Josephson Voltage Standard that will be operated on the watt balance experiment. The device has been designed to bias separately all of the 13 independent segments of the Josephson array in order to be able to track the induced voltage across the moving coil during the constant velocity and acceleration phases. It is powered from Lithium-ion batteries in order to avoid electrical offsets originating from ground loops and to allow long series of measurements.

A very low thermal EMFs computer-controlled scanner

Some National Metrology Institutes have shown an interest to build a copy of our very low thermal electromotive forces (EMFs) scanner since we designed it in our laboratory a few years ago. This device has been developed to calibrate up to 12 Zener-based voltage standards by comparison to a programmable Josephson voltage standard but can be implemented in any set-up that requires electrical contacts with a repeatability of the residual EMFs at the nanovolt level. This paper describes the technical details which explain why this device still shows an impressive robustness in its metrological characteristics after one hundred of thousands connections since its first installation. We present the result of a statistical analysis of a long series of measurements using the Allan variance, which demonstrates sub-nanovolt residual thermal EMFs.

Direct comparison of Josephson Voltage Standards at 10 V between BIPM and CENAM

A direct comparison of Josephson Voltage Standards (JVS) at 10 V between the Bureau International des Poids et Mesures (BIPM) and the Centro Nacional de Metrología (CENAM), México, was carried out in September 2011. This comparison is part of the BIPM key comparisons (BIPM.EM-K10.b), and took place in the new DC voltage laboratory of CENAM. The relative voltage difference between the two quantum standards was -6 parts in 1011 (-0.6 nV), with a relative Type A uncertainty of 4.5 parts in 1011 (0.45 nV). The total combined uncertainty of the comparison is under evaluation.