Status of the BIPM Watt Balance

Fang, Hao; Kiss, A.; Mirandes, E. de; Jiang, Lan; Robertsson, L.; Solve, S; Picard, A.; Stöck, M

doi:10.1109/tim.2012.2225930

Cited by 25 publications

(32 citation statements)

References 7 publications

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“…A similar watt balance magnet is employed in many NMI watt balances, e.g. the BIPM watt balance [5], METAS-II watt balance [4], NIST-4 watt balance [15], KRISS watt balance [16].…”

Section: Review Of An Ideal Case With 1/r Magnetic Fieldmentioning

confidence: 99%

“…A handful of national metrology institutes (NMIs) have designed and constructed watt balances [1][2][3][4][5][6][7], a high-precision force comparator leading the effort in redefining the SI unit of mass, the kilogram (kg), in terms of the Planck constant h, expected to culminate in 2018 [8]. A watt balance experiment is comprised of two modes of operation, i.e.…”

Section: Introductionmentioning

confidence: 99%

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A discussion ofBlconservation on a two dimensional magnetic field plane in watt balances

Zhao

Huang

2016

Meas. Sci. Technol.

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The watt balance is an experiment being pursued in national metrology institutes for precision determination of the Planck constant h. In watt balances, the 1/r magnetic field, expected to generate a geometrical factor Bl independent to any coil horizontal displacement, can be created by a strict two dimensional, symmetric (horizontal r and vertical z) construction of the magnet system. In this paper, we present an analytical understanding of magnetic field distribution when the r symmetry of the magnet is broken and the establishment of the Bl conservation is shown. By using either Gauss's law on magnetism with monopoles or conformal transformations, we extend the Bl conservation to arbitrary two dimensional magnetic planes where the vertical magnetic field component equals zero. The generalized Bl conservation allows a relaxed physical alignment criteria for watt balance magnet systems. II. REVIEW OF AN IDEAL CASE WITH 1/r MAGNETIC FIELDThe analysis in this article is based on one of the most popular watt balance magnets employed 4,5,15,16 . Figure 1 shows the construction of the magnet with a symmetrical structure in both the r and z axes. The magnetic flux, generated by two permanent magnet disks oriented in repulsion, is guided by yokes of high permeability material through an air gap radi-

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“…A similar watt balance magnet is employed in many NMI watt balances, e.g. the BIPM watt balance [5], METAS-II watt balance [4], NIST-4 watt balance [15], KRISS watt balance [16].…”

Section: Review Of An Ideal Case With 1/r Magnetic Fieldmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A discussion ofBlconservation on a two dimensional magnetic field plane in watt balances

Zhao

Huang

2016

Meas. Sci. Technol.

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“…In this experiment, the watt balance was mounted on an optical table without any vibration isolation and was composed of simplified components and measurement facilities. The fully operational apparatus was capable of producing Planck constant values with a type A uncertainty of 10 −6 and a type B uncertainty of the order of 10 −5 [6]. The type A uncertainty was limited mainly by the poor laboratory environment whereas the type B uncertainty was limited mainly by alignment capabilities.…”

Section: Bipm Watt Balancementioning

confidence: 99%

“…The results are deduced from a single measurement with the coil moving upwards. We mention that the new measurements were carried out using a bifilar coil [6] instead of a single working coil. The wire length of each winding of the bifilar coil is thus approximately half of that of the normal working coil.…”

Section: Improvementmentioning

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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“…The BIPM is developing a novel watt balance in order to realize the forthcoming new definition of the kilogram in terms of the Planck constant, h, at the 10 -8 level [1]. A type A uncertainty of about 10 −6 and a type B uncertainty of several parts in 10 −5 was achieved using the first experiment conducted in a non-ideal environment inside a temporary laboratory.…”

Section: Introductionmentioning

confidence: 99%

Update from the BIPM watt balance

Fang

Kiss

Lavergne

et al. 2014

29th Conference on Precision Electromagnetic Measurements (CPEM 2014)

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This paper reports the latest progress made on the BIPM watt balance project. The type A uncertainty of the Planck constant measurements was reduced from 1.4 parts in 10 6 to about 5 parts in 10 7 . The new magnet was successively fabricated and assembled with an expected high uniformity of the flux density of several parts in 10 4 . Several new components are being introduced into the apparatus which we expect to reduce the type B measurement uncertainty significantly.

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Status of the BIPM Watt Balance

Cited by 25 publications

References 7 publications

A discussion ofBlconservation on a two dimensional magnetic field plane in watt balances

A discussion ofBlconservation on a two dimensional magnetic field plane in watt balances

Recent progress on the BIPM watt balance

Update from the BIPM watt balance

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