Determination of the Volt by Means of Voltage Balances

Bego, V.

doi:10.1088/0026-1394/25/3/001

Cited by 18 publications

(6 citation statements)

References 5 publications

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“…This design was the choice of CSIRO in Australia. Bego [43] compares the design options and results. Schematically drawn in figure 4, the area between a fixed plate and a pool of liquid mercury forms a capacitive force region.…”

Section: Absolute Volt Balance: the Link To Simentioning

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: Absolute Volt Balance: the Link To Simentioning

confidence: 99%

History and progress on accurate measurements of the Planck constant

Steiner

2012

Rep. Prog. Phys.

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“…An alternative approach is to realise a derived electromagnetic unit instead of the base unit ampere. The volt balance [7] is the electrostatic analogue of the ampere balance: the force develops between two electrodes at different electrostatic potentials. The electrodes of the volt bal-ance can have a much simpler geometry than the windings of the ampere balance; they can be flat surfaces or cylinders.…”

Section: The Mechanical Ampere: 1948-2019mentioning

confidence: 99%

A quantum ampere

Callegaro

2020

Tm - Technisches Messen

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The revision of the International System of Units (SI), implemented since 20 May 2019, has redefined the unit of electric current, the ampere ( A), linking it to a fixed value of the elementary charge. This paper discusses the new definition and the realisation of the electrical units by quantum electrical metrology standards, which every year become more and more accessible, reliable and user friendly.

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“…In this way, a link between the test mass and the Planck constant is established. In a typical set-up (see [17] for a review), the voltage needed is around 10 kV and the test mass is a few grams. Using this approach, Funck and Sienknecht from the Physikalisch-Technische Bundesanstalt (PTB) [18] reached a relative standard uncertainty of 6.3×10 −7 in the determination of h [19].…”

Section: Voltage Balancementioning

confidence: 99%

Tracing Planck's constant to the kilogram by electromechanical methods

2003

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Among the priority tasks in the further development of the International System of Units is the redefinition of the kilogram based on fundamental constants. One of the strategies pursued today is to relate mass to Planck's constant h using the equivalence between mechanical and electrical energies. In this paper, possible experimental approaches in this direction are described. The approach which promises to reach the required uncertainty at the earliest is the concept of the moving-coil watt balance. The status of the different watt balance experiments is reviewed in detail.

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Determination of the Volt by Means of Voltage Balances

Cited by 18 publications

References 5 publications

History and progress on accurate measurements of the Planck constant

History and progress on accurate measurements of the Planck constant

A quantum ampere

Tracing Planck's constant to the kilogram by electromechanical methods

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