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Session:

1E - Key, Regional and Interlaboratory Comparisons 

Date & Time:

Monday August 7, 10:45 AM - 12:15 PM

Paper Title:

An Overview of Josephson Voltage Standard Interlaboratory Comparison 

 

 

Speaker:

Dr. Yi-hua Tang  

CoAuthors:

Speaker Info

Company:

NIST

Department:

Quantum Electrical Metrology Division

Address:

100 Bureau Drive , Bldg.220, Rm.B258
Gaithersburg, MD, 20899, United States

Phone:

301 975 4691

Fax:

301 975 2115

Email:

yi-hua.tang@nist.gov 

 

 

Abstract:

Josephson voltage standard (JVS) system is widely used as the primary voltage standard in many national metrology institutes around the world. A traditional "traceability path" of an unbroken chain of comparisons to stated references does not apply to the case of JVS operated in different locations. However, the equivalence of JVS used by different laboratories must be demonstrated through intercomparisons. This paper reviews the protocols for JVS intercomparison developed in the last decade. The majority of the JVS intercomparisons used by the Bureau International des Poids et Mesures (BIPM) Key Comparison and the National Conference of Standard Laboratories International Josephson Voltage Standard Interlaboratory Comparison (NCSLI JVS ILC) have been performed by using Zener voltage transfer standards and a protocol based on the Measurement Assurance Program (MAP). The uncertainty of such a comparison is in the range of few parts in 10^8 at 10 V, limited by the Zener characteristics. In order to improve the uncertainty in the comparison, protocols using the compact Josephson voltage standard (CJVS) as transfer standard have been developed. The uncertainty using these protocols can be in the range of few parts in 10^9 at 10 V, so that JVS system errors at the level of few parts in 10^9 can be detected and corrected. The BIPM has also sponsored many array-to-array direct comparisons with national metrology institutes. This is the ultimate comparison with an uncertainty of a few parts in 10^10 at the 10 V level. Because the Josephson junction array developed during 1980's used the intrinsically non-stable voltage steps, the direct comparisons used by BIPM were difficult to carry out. In 1997 a new type of Josephson junction array using non-zero current bias voltage steps was developed. Using such new devices the array-to-array direct comparison is much quicker and easier to perform, and uncertainties can be improved by at least an order of magnitude compared to the Zener MAP. This paper will use examples to illustrate various protocols in JVS comparisons. The uncertainty analysis using real JVS comparison data will be demonstrated. New developments and future perspective in the JVS comparison will also be discussed.  

 

 

 

 

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