Coils used in the Joule Balance at the NIM

Zhang, Z.; Li, Z.; Han, Bing; Lu, Yunfeng; Li, S.; Xu, Jinxin; Wang, G.; Gong, H.

doi:10.1109/cpem.2014.6898423

Cited by 4 publications

(6 citation statements)

References 3 publications

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“…The original NIM joule balance design [ 28 ] replaced the moving mode of the Kibble balance with measurements of mutual inductance [ 29 ] between two stationary coils: the coil which generates the field for the weighing mode (the exciting coil) and the movable coil [ 30 ]. Each measurement is made by applying a linear current ramp to the field generating coil which induces a constant voltage in the stationary movable coil, similar to [ 31 ].…”

Section: The Kibble Balancementioning

confidence: 99%

“…The resulting equation relates virtual energies which gives rise to the name of the technique. The first generation joule balance reported results in 2014 [ 28 ] but heating effects and problems with mutual inductance measurement have concentrated future work onto its successor which is described in section 2.2.1 and no longer measures mutual inductance.…”

Section: The Kibble Balancementioning

confidence: 99%

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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: The Kibble Balancementioning

confidence: 99%

Section: 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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“…To get a number for the Planck constant h with an uncertainty below 0.1 ppm, a new generation of the joule balance apparatus (NIM-2) system was started in 2013. To solve the problem of self-heating in the coils, ferromagnetic materials are used in the coil system to strengthen the magnetic field, and this led to a reduction in the power consumption of the coils to 7.5 W [7]. However, using this solution, when the mutual inductance is measured the current in the exciting coils has to be changed, which will create a considerable measurement uncertainty from the nonlinearity and hysteresis of the ferromagnetic material.…”

Section: Introductionmentioning

confidence: 99%

A determination of the Planck constant by the generalized joule balance method with a permanent-magnet system at NIM

Zhang

et al. 2016

Metrologia

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The joule balance experiment has been carried out at the National Institute of Metrology, China (NIM) since 2007. By the end of 2013 the first generation of the joule balance (NIM-1) achieved a measurement uncertainty of 7.2 × 10 −6 (k = 1). To reduce the measurement uncertainty further, the next generation of the joule balance apparatus (NIM-2) system is under construction. A new coil system using ferromagnetic material is being adopted in NIM-2 to reduce self-heating in the coils. However, the effects on the measurement of the mutual inductance from the nonlinearity and hysteresis of the ferromagnetic material will bring a considerable measurement uncertainty. Inspired by the watt balance, the measurement of the mutual inductance is replaced by an equivalent measurement of the magnetic flux linkage difference. The nonlinearity and hysteresis will not be a problem in the measurement of the magnetic flux linkage difference. This technique comes from the watt balance method. It is called the generalized joule balance method, which is actually a modification of the watt balance method. However, it still represents a valid change that can reduce the difficulty of dynamic measurement experienced using the watt balance. Permanent magnets can also be adopted in the generalized joule balance. To check the feasibility of the generalized joule balance method, some preliminary experiments have been performed on NIM-1. A yokeless permanent magnet system has been designed and used to replace the exciting coils in NIM-1. In this paper, the structure of the yokeless permanent magnet system is introduced. Furthermore, a determination of the Planck constant with the permanent magnet system is presented. The value of the Planck constant h we obtained is 6.626 069(17) × 10 −34 J s with a relative standard uncertainty of 2.6 × 10 −6 .

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“…11 [15]. The idea is from the consideration that if the ferromagnetic material is used to short the magnetic path between the exciting and movable coils, the efficiency of the magnetic field can be increased a lot.…”

Section: Electromagnetmentioning

confidence: 99%

“…In addition, the current in the suspended coil has to be changed and the nonlinear characteristic and hysteresis will bring a big problem. A new approach named the magnetic flux linkage measurement is proposed and details are presented in [15].…”

Section: Electromagnetmentioning

confidence: 99%

The Improvement of Joule Balance NIM-1 and the Design of New Joule Balance NIM-2

Zhang

et al. 2015

IEEE Trans. Instrum. Meas.

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The development of the joule balance method to measure the Planck constant, in support of the redefinition of the kilogram, has been going on at the National Institute of Metrology of China (NIM) since 2007. The first prototype has been built to check the feasibility of the principle. In 2011, the relative uncertainty of the Planck constant measurement at NIM is 7.7 × 10 −5 . Self-heating and swing of the coils are the main uncertainty contributions. Since 2012, some improvements have been made to reduce these uncertainties. The relative uncertainty of the joule balance is reduced to 7.2 × 10 −6 at present. The Planck constant measured with the joule balance is h = 6.6261041(470) × 10 −34 Js. The relative difference between the determined h and the CODATA2010 recommendation value is 5×10 −6 . Further improvements are still being carried out on the NIM-1 apparatus. At the same time, the design and construction of a brand new and compact joule balance NIM-2 are also in progress and presented here. Index Terms-International system of units (SI), joule balance, kilogram, Planck's constant, redefinition, uncertainty.0018-9456

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Coils used in the Joule Balance at the NIM

Cited by 4 publications

References 3 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

A determination of the Planck constant by the generalized joule balance method with a permanent-magnet system at NIM

The Improvement of Joule Balance NIM-1 and the Design of New Joule Balance NIM-2

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