On the development of large Josephson series arrays for voltage standards of high precision

Niemeyer, J.

doi:10.1109/tim.1987.6312680

Cited by 8 publications

(2 citation statements)

References 18 publications

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“…As fabrication capabilities came to realize these designs, 1984 spawned the next generation of Josephson voltage devices. A single device could generate voltages at the 1 V level, as described in [64] and in [65]. This eliminated the uncertainties associated with ratio conversions of millivolts to the characteristic 1.018 V Weston cell voltage.…”

Section: The Misinterpreted Volt Determinationsmentioning

confidence: 99%

History and progress on accurate measurements of the Planck constant

Steiner

2012

Rep. Prog. Phys.

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The measurement of the Planck constant, h, is entering a new phase. The CODATA 2010 recommended value is 6.626 069 57 × 10(-34) J s, but it has been a long road, and the trip is not over yet. Since its discovery as a fundamental physical constant to explain various effects in quantum theory, h has become especially important in defining standards for electrical measurements and soon, for mass determination. Measuring h in the International System of Units (SI) started as experimental attempts merely to prove its existence. Many decades passed while newer experiments measured physical effects that were the influence of h combined with other physical constants: elementary charge, e, and the Avogadro constant, N(A). As experimental techniques improved, the precision of the value of h expanded. When the Josephson and quantum Hall theories led to new electronic devices, and a hundred year old experiment, the absolute ampere, was altered into a watt balance, h not only became vital in definitions for the volt and ohm units, but suddenly it could be measured directly and even more accurately. Finally, as measurement uncertainties now approach a few parts in 10(8) from the watt balance experiments and Avogadro determinations, its importance has been linked to a proposed redefinition of a kilogram unit of mass. The path to higher accuracy in measuring the value of h was not always an example of continuous progress. Since new measurements periodically led to changes in its accepted value and the corresponding SI units, it is helpful to see why there were bumps in the road and where the different branch lines of research joined in the effort. Recalling the bumps along this road will hopefully avoid their repetition in the upcoming SI redefinition debates. This paper begins with a brief history of the methods to measure a combination of fundamental constants, thus indirectly obtaining the Planck constant. The historical path is followed in the section describing how the improved techniques and discoveries in quantum mechanics steadily reduced the uncertainty of h. The central part of this review describes the technical details of the watt balance technique, which is a combination of the mechanical and electronic measurements that now determine h as a direct result, i.e. not requiring measured values of additional fundamental constants. The first technical section describes the basics and some of the common details of many watt balance designs. Next is a review of the ongoing advances at the (currently) seven national metrology institutions where these experiments are pursued. A final summary of the recent h determinations of the last two decades shows how history keeps repeating itself; there is again a question of whether there is a shift in the newest results, albeit at uncertainties that are many orders of magnitude less than the original experiments. The conclusion is that there is room for further development to resolve these differences and find new ideas for a watt balance system with a more universal application. Sin...

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Section: The Misinterpreted Volt Determinationsmentioning

confidence: 99%

History and progress on accurate measurements of the Planck constant

Steiner

2012

Rep. Prog. Phys.

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“…A separate and adjustable dc bias was necessary for each junction. The availability of arrays of Josephson junctions that can be operated in a near-zero biased mode [8,9] now makes possible the design of a Josephson potentiometer that is simpler to operate than the apparatus described in Ref. [7].…”

Section: Rh (4)) a Commercially Available DC Potentiometermentioning

confidence: 99%

Present State of Quantized-Hall-Resistance Metrology

Delahaye

1988

Metrologia

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The experimental techniques used by the national institutes of metrology to measure the quantized Hall resistance in terms of their representations of the ohm are described. The agreement among these measurements is examined using the results of the comparisons of national standards of electrical resistance (1 SZ) made at the BIPM.The results of measurements of the quantized Hall resistance in SI units using calculable standards of capacitance are also examined and compared with indirect evaluations based on the determination of different fundamental constants.

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