Research on the effect of the external magnetic field in the joule balance at NIM

Xu, Jinxin; You, Qiang; Li, Zhengkun; Bai, Yang; Lu, Yunfeng; Zhang, Zhonghua; He, Qing

doi:10.1088/1681-7575/aabec2

Cited by 7 publications

(10 citation statements)

References 23 publications

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“…the deviation of 'Mean' relative to the main flux linkage difference of 46.0 Vs. By taking the difference between δψ ′ v and δψ v , the value of δψ e can be calculated as 1.84(2)×10 −5 Vs, which yields a deviation of 4.1(1)×10 −7 relative to the main flux linkage difference. Note that, the same deviation previously evaluated in [16] is less than 2 × 10 −7 . This inconsistency is mainly caused by the following two reasons.…”

Section: Experiments and Analysissupporting

confidence: 72%

“…magnetic head screwdriver) would result in a significant decrease of the relative permeability of the Ni-Fe alloy. However, in the simulation in [16], the relative permeability of the shield is constantly set as 50 000. Second, from 2018 to 2019, some improvements have been performed in the joule balance, e.g.…”

Section: Experiments and Analysismentioning

confidence: 99%

“…In the joule balance, the relative movement between the coil-suspension system and the main magnetic field is realized by the movement of the permanent magnet system. The consequent disadvantage is that the mass measurement result will be affected by the effect of the external magnetic field [16]. Therefore, two solutions were proposed in [17] to overcome this problem, i.e.…”

Section: Introductionmentioning

confidence: 99%

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The interaction between the magnetized coil-suspension system and the compensation coil in the joule balance

Li¹,

Xu²,

Li³

et al. 2020

Metrologia

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The joule balance is one of the mass traceability devices in the revised International System of Units, and its smooth operation relies on a compensation coil to reduce the effect of the external magnetic field. In this paper, the interaction between the magnetized coil-suspension system and the compensation coil is theoretically analyzed and experimentally verified. First, an additional induced voltage can be detected in the compensation coil when it moves relative to the magnetized coil-suspension system, which will lead to a measurement deviation of several parts in 10 6 in the moving phase. Second, if the excitation current also flows through the compensation coil in the weighing phase, then an additional magnetization force which can not be canceled out by the mass-on and mass-off measurements will be applied on the coil-suspension system. Theoretical analysis indicates that the deviations introduced in the two phases are nearly equivalent, so that the final mass measurement result will not be affected at least on the magnitude of 10 −9 . However, this conclusion can only be verified at 10 −8 level due to the current measurement limitations of the joule balance.

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Section: Experiments and Analysissupporting

confidence: 72%

Section: Experiments and Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The interaction between the magnetized coil-suspension system and the compensation coil in the joule balance

Li¹,

Xu²,

Li³

et al. 2020

Metrologia

Self Cite

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“…the earth magnetic flux, very well. Magnetic flux from close sources can, however, penetrate the magnet system [69]. Not always does such parasitic flux lead to systematic effects.…”

Section: Shielding Performancementioning

confidence: 99%

“…The relative bias caused by an external field can reach the ∼ 10 −7 . By adding additional shielding, the relative bias can be reduced to ∼ 10 −8 [69,70].…”

Section: Shielding Performancementioning

confidence: 99%

The irony of the magnet system for Kibble balances -- a review

Li,

Schlamminger

2021

Preprint

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The magnet system is an essential component of the Kibble balance, a device that is used to realize the unit of mass. It is the source of the magnetic flux, and its importance is captured in the geometric factor Bl. Ironically, the Bl factor cancels out and does not appear in the final Kibble equation. Nevertheless, care must be taken to design and build the magnet system because the cancellation is perfect only if the Bl is the same in both modes: the weighing and velocity mode. This review provides the knowledge necessary to build a magnetic circuit for the Kibble balance. In addition, this article discusses the design considerations, parameter optimizations, practical adjustments to the finished product, and an assessment of systematic uncertainties associated with the magnet system.

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The upgrade of NIM-2 joule balance since 2017

Bai

et al. 2020

Metrologia

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In 2017, we published the first measurement result with the NIM-2 joule balance and the relative standard uncertainty was 2.4 × 10 −7 . Since then, a series of improvements have been carried out to upgrade the NIM-2 joule balance towards the 10 -8 level relative uncertainty. The main improvements include a permanent magnet, as well as a two-layer magnetic shield to decrease the main uncertainty contribution from the external magnetic field, a parasitic displacement measurement system and a new suspension for improving alignments, and a new mass translation stage constructed with all non-magnetic materials. In September 2019, when the NIM-2 joule balance was used to calibrate a 1 kg mass, the type A relative standard uncertainty had been reduced to 3 × 10 −8 (k = 1) and the combined relative standard uncertainty was less than 1 × 10 −7 (k = 1). In October and November 2019, a 1 kg Pt/Ir mass and a 1 kg stainless steel mass were measured with the NIM-2 joule balance, and the relative standard uncertainties were 5.2 × 10 −8 and 6.5 × 10 −8 , respectively. The relative difference between the measured values and the calibration values obtained from the mass group were 4 × 10 −9 and 3 × 10 −8 , respectively.

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Research on the effect of the external magnetic field in the joule balance at NIM

Cited by 7 publications

References 23 publications

The interaction between the magnetized coil-suspension system and the compensation coil in the joule balance

The interaction between the magnetized coil-suspension system and the compensation coil in the joule balance

The irony of the magnet system for Kibble balances -- a review

The upgrade of NIM-2 joule balance since 2017

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