Determination of the Planck constant with the METAS watt balance

Eichenberger, A.; Baumann, Henri; Jeanneret, B.; Jeckelmann, B.; Richard, Philippe; Beer, W.

doi:10.1088/0026-1394/48/3/007

Cited by 99 publications

(77 citation statements)

References 27 publications

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“…Several scientific publications from 2007 to 2017 [18][19][20][21][22][23][24][25][26][27] were analysed from the position of the relative and comparative uncertainty values reached. The data are summarized in Table 1.…”

Section: Applications Of µ Si For Plank Constant Measurementmentioning

confidence: 99%

Plank’s Constant: Evaluation of Measurement Uncertainty

Menin¹,

Expert²

2018

NHMP

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Abstract. In this article, we present a new metric called the comparative uncertainty, according to which the least achievable relative uncertainty is calculated when measuring the Planck constant. To calculate the comparative uncertainty, information theory is used. The optimizing criterion is the number of quantities considered in the model. Its calculation is possible due to the fact that any model contains a certain amount of information about the object under study. Comparative uncertainty can be verified by field trials or computer simulations within a specified range of changes of the Planck constant. The concept of introduced uncertainty is universal and can be recommended for estimating the accuracy of measurements in the study of physical phenomena and technological processes. Examples of application of the proposed approach are discussed.

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Section: Applications Of µ Si For Plank Constant Measurementmentioning

confidence: 99%

Plank’s Constant: Evaluation of Measurement Uncertainty

Menin¹,

Expert²

2018

NHMP

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“…This allows the balance to be always in an equilibrium position and avoids problems of hysteresis, but this requires a coil transfer between the balance suspension, for the static measurement, and the mechanical translation 'seesaw' system, for the dynamic phase. The work on the METAS watt balance has now led to a published result [27] with a relative uncertainty of 2.9 parts in 10 7 . This uncertainty is dominated by alignment issues and the present apparatus has reached its limits.…”

Section: The Existing Watt Balance Experimentsmentioning

confidence: 99%

The watt balance: determination of the Planck constant and redefinition of the kilogram

Stöck

2011

Phil. Trans. R. Soc. A.

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Since 1889, the international prototype of the kilogram has served as the definition of the unit of mass in the International System of Units (SI). It is the last material artefact to define a base unit of the SI, and it influences several other base units. This situation is no longer acceptable in a time of ever-increasing measurement precision. It is therefore planned to redefine the unit of mass by fixing the numerical value of the Planck constant. At the same time three other base units, the ampere, the kelvin and the mole, will be redefined. As a first step, the kilogram redefinition requires a highly accurate determination of the Planck constant in the present SI system, with a relative uncertainty of the order of 1 part in 10 8 . The most promising experiment for this purpose, and for the future realization of the kilogram, is the watt balance. It compares mechanical and electrical power and makes use of two macroscopic quantum effects, thus creating a relationship between a macroscopic mass and the Planck constant. In this paper, the operating principle of watt balance experiments is explained and the existing experiments are reviewed. An overview is given of all available experimental determinations of the Planck constant, and it is shown that further investigation is needed before the redefinition of the kilogram can take place. Independent of this requirement, a consensus has been reached on the form that future definitions of the SI base units will take.

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“…As a result, the Planck constant h can be related to the test mass m by comparing the electrical power to the mechanical power in conjunction with the quantum Hall effect [3] and the Josephson effect [4]. Since the proposal in 1975, the watt balance has been widely spread and persuaded at many national metrology institutes (NMIs) [5][6][7][8][9][10][11][12][13]. The detailed principle and recent progress of watt balance experiments at NMIs can be found in several review papers, e.g., [14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Field representation of a watt balance magnet by partial profile measurements

Yuan

Zhao

et al. 2015

Metrologia

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Abstract. Permanent magnets with high-permeability yokes have been widely used in watt balances for supplying a robust and strong magnetic field at the coil position. Subjected to the mechanical realization, only several B r (z) (radial magnetic field along the vertical direction) profiles can be measured by coils for field characterization. In this article, we present an algorithm that can construct the global magnetic field of the air gap based on N (N ≥ 1) additional measurements of B r (z) profiles. The proposed algorithm is realized by polynomially estimating the B z (r) function with analysis of basic relations between two magnetic components in air gap, i.e., B r (r, z) and B z (r, z), following the Maxwell's equations. The algorithm, verified by FEM simulations, can characterize the three-dimensional contribution of the magnetic field for a watt balance magnet with acceptable accuracy, which would supply basic field parameters for alignment and misalignment corrections.

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Determination of the Planck constant with the METAS watt balance

Cited by 99 publications

References 27 publications

Plank’s Constant: Evaluation of Measurement Uncertainty

Plank’s Constant: Evaluation of Measurement Uncertainty

The watt balance: determination of the Planck constant and redefinition of the kilogram

Field representation of a watt balance magnet by partial profile measurements

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