Methods for aligning the NIST watt-balance

Stenbakken, Gerard N.; Steiner, Reto; Olsen, P. T.; Williams, A.E.

doi:10.1109/19.492750

Cited by 12 publications

(8 citation statements)

References 5 publications

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“…All existing Kibble balances require precise alignment of both the magnet and the coil [125][126][127]. The arguments in section 2.1 show that, for balances which have a common weighing and moving mechanism, the alignment requirements may be relaxed, due to the cancellation of the effects of the derivatives of the flux with respect to the non vertical directions [15].…”

Section: Alignment Of the Kibble Balancementioning

confidence: 99%

The watt or Kibble balance: a technique for implementing the new SI definition of the unit of mass

2016

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The redefinition of the SI unit of mass in terms of a fixed value of the Planck constant has been made possible by the Kibble balance, previously known as the watt balance. Once the new definition has been adopted, the Kibble balance technique will permit the realisation of the mass unit over a range from milligrams to kilograms. We describe the theory underlying the Kibble balance and practical techniques required to construct such an instrument to relate a macroscopic physical mass to the Planck constant with an uncertainty, which is achievable at present, in the region of 2 parts in 10 8 . A number of Kibble balances have either been built or are under construction and we compare the principal features of these balances.

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Section: Alignment Of the Kibble Balancementioning

confidence: 99%

The watt or Kibble balance: a technique for implementing the new SI definition of the unit of mass

2016

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“…A system which allows the coil to be clamped and unclamped has been described in [43]. A detailed description of alignment methods is found in [50,51].…”

Section: Considerations For Future Watt Balancesmentioning

confidence: 99%

Watt balance experiments for the determination of the Planck constant and the redefinition of the kilogram

Stöck¹

2012

Metrologia

106

138

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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 background for the choice of the Planck constant for the kilogram redefinition is discussed and the role of the Planck constant in physics is briefly reviewed. The operating principle of watt balance experiments is explained and the existing experiments are reviewed. An overview is given of all presently 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. * This article is based on a lecture given at the International School of Physics 'Enrico Fermi', Course CLXXXV: Metrology and Physical Constants, held in Varenna on 17-27 July 2012. It will also be published in the proceedings of the school, edited by E Bava, M Kühne and A M Rossi (IOS Press, Amsterdam and SIF, Bologna).

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“…Extrapolating between measurements at differing trim current settings achieves a sensitivity to about 10 µA out of the approximately 35 mA. A magnetic field modeling program, adapted from the original design calculations for the superconducting solenoid [ 10 ], revealed that the non-1/ r deviation across the induction coil’s dimensions is about 600 parts in 10 6 . Both these constant current sources have low noise and typical drift of less than 50 pA per day.…”

Section: Apparatus Descriptionsmentioning

confidence: 99%

“…Detailed modeling and calculations of the alignment sensitivities can be found in Refs. [ 10 ] and [ 11 ]. We make the following alignments in this order: 1) Align the axis of the superconducting solenoid to vertical.…”

Section: Preliminary Experiments Setup Environment Control Noise mentioning

confidence: 99%

Details of the 1998 watt balance experiment determining the Planck constant

Steiner¹,

Newell²,

Williams³

2005

J. Res. Natl. Inst. Stand. Technol.

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The National Institute of Standards and Technology (NIST) watt balance experiment completed a determination of Planck constant in 1998 with a relative standard uncertainty of 87 × 10−9 (k = 1), concurrently with an upper limit on the drift rate of the SI kilogram mass standard. A number of other fundamental physical constants with uncertainties dominated by this result are also calculated. This paper focuses on the details of the balance apparatus, the measurement and control procedures, and the reference calibrations. The alignment procedures are also described, as is a novel mutual inductance measurement procedure. The analysis summary discusses the data noise sources and estimates for the Type B uncertainty contributions to the uncertainty budget. Much of this detail, some historical progression, and a few recent findings have not been included in previous papers reporting the results of this experiment.

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Methods for aligning the NIST watt-balance

Cited by 12 publications

References 5 publications

The watt or Kibble balance: a technique for implementing the new SI definition of the unit of mass

The watt or Kibble balance: a technique for implementing the new SI definition of the unit of mass

Watt balance experiments for the determination of the Planck constant and the redefinition of the kilogram

Details of the 1998 watt balance experiment determining the Planck constant

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