The BIPM Watt Balance: Improvements and Developments

Picard, A.; Bradley, Michael P.; Fang, Hao; Kiss, A.; Mirandes, E. de; Parker, B.; Solve, S; Stöck, M

doi:10.1109/tim.2011.2126130

Cited by 33 publications

(26 citation statements)

References 8 publications

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“…The BIPM watt balance has the unique capability of implementing both the conventional two-phase and the simultaneous measurement schemes [4,5]. The novel simultaneous approach of the BIPM watt balance makes the experiment less sensitive to some of the factors limiting the conventional approach.…”

Section: Bipm Watt Balancementioning

confidence: 99%

Recent progress on the BIPM watt balance

Fang

Kiss

Robertsson

et al. 2014

EPJ Web of Conferences

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Abstract. We present the recent progress on the BIPM (Bureau International des Poids et Mesures) watt balance. The existing apparatus was transferred to the dedicated new laboratory with better thermal and vibrational conditions. The apparatus is fully operational in air. An improvement by a factor of three was achieved on the S/N ratio of both the voltage-to-velocity and force-to-current ratios. The fabrication of the parts of the new magnet is completed and its assembly is finished.

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Section: Bipm Watt Balancementioning

confidence: 99%

Recent progress on the BIPM watt balance

Fang

Kiss

Robertsson

et al. 2014

EPJ Web of Conferences

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“…At the BIPM, development of a watt balance began in 2003. The BIPM approach is to carry out the static and dynamic phases simultaneously [29,30], but to avoid direct energy conversion, the importance of which is discussed above. The derivation of the watt balance measurement equation (3.9) depends on the term B r L being constant between both phases; otherwise, corrections are necessary.…”

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%

“…But one disadvantage for such magnetic circuit is that the magnetic field gradient in the horizontal direction is obviously increased, which may bring difficulties for the alignment [17]. As is noticed, the alignment is one of the most difficult procedures in operating a watt balance, and several techniques that can relax the alignment have been proposed: the simultaneous measurement of two operating modes has been carried out in watt balance at the Bureau International des Poids et Mesures (BIPM) [8], which has been further developed by Dr. I A Robinson in [18]; new experimental designs of watt balances, of course, can relax the alignment [19].…”

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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The BIPM Watt Balance: Improvements and Developments

Cited by 33 publications

References 8 publications

Recent progress on the BIPM watt balance

Recent progress on the BIPM watt balance

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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