Coils and the Electromagnet Used in the Joule Balance at the NIM

Zhang, Zhonghua; Li, Zhengkun; Han, Bing; Lu, Yunfeng; Li, Shisong; Xu, Jinxin; Wang, Gang

doi:10.1109/tim.2015.2406055

Cited by 25 publications

(19 citation statements)

References 18 publications

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“…Note that, a determination of the Planck constant with a relative standard uncertainty of 2.4 × 10 −7 has been published in 2017 based on the joule balance [2]. At that time, the compensation coil was energized in the weighing phase to overcome the magnetic saturation of the electromagnet, and it was also used in the moving phase to reduce the effect of the external magnetic field [22]. Therefore, the Planck constant measurement result published in 2017 was not affected by the interaction between the magnetized coil-suspension system and the compensation coil.…”

Section: Discussionmentioning

confidence: 99%

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: Discussionmentioning

confidence: 99%

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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“…This is ensured by placing the compensation coils sufficiently close to the suspended coil. Although the idea of compensation coils is neat, mechanical difficulties may arise while placing three coils in the air gap [40], [41].…”

Section: Faraday's Law Of Inductionmentioning

confidence: 99%

“…The asymmetry between Faraday's Law and Amperes Law can be treated with compensating coils, as proposed by the NIM Joule Balance Group [40], [41]. We have introduced an alternative approach where, under certain circumstances, the asymmetry could be accounted for without compensation coils by means of a magnetic gradiometer.…”

Section: Monitoring the Change In Magnetic Flux Densitymentioning

confidence: 99%

External Magnetic Field Measurements in UME Kibble Balance

Ahmedov¹,

Korutlu²,

Dorosinskiy³

et al. 2020

ACTA IMEKO

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The new definition of kilogram in terms of the fixed value of Planck constant ensures the long-term stability of SI mass unit and enables traceability from more than one source. Kibble balance experiments offer an effective primary realization method for the new definition of kilogram. Kibble Balance apparatus operating at National Metrology Institute of Turkey is designed with a stationary coil and an oscillating magnet. In contradistinction to traditional moving coil Kibble balance experiments, external magnetic field brings an asymmetry between the Ampere’s law of force and the Faraday’s law of induction in moving magnet experiments. In this paper, we develop a method based on the external magnetic flux density difference measurements in vertical direction to take into account the effect of the external magnetic field on the realization of kilogram. The proposed model in this approach fits well with the data such that the kilogram realization requirement is met within the accuracy of the measuring instrument.

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“…The mutual inductance measurement is one of the key techniques in the joule balance [1,2], and it is applied in a coil magnet system with air core. In that magnet system, due to the low efficiency of the current in the exciting coil producing useful magnetic field, a rather large current is required for weighing mode [3], and the coil heating is an important uncertainty source [4].…”

Section: Introductionmentioning

confidence: 99%

“…To decrease the self-heating and increase the efficiency of the magnetic field, an electromagnet with a closed ferromagnetic path using high permeability material was designed [3]. In this electromagnet system, measuring the magnetic flux linkage difference of a suspended coil at two vertical positions is proposed to replace the previous mutual inductance measurement [3]. The flux linkage difference can be obtained directly by integrating the induced voltage u(t) from the suspended coil relative to the moving electromagnet.…”

Section: Introductionmentioning

confidence: 99%

Stepwise compensation waveform generation by using Josephson voltage standards for joule balance

Wang

You

et al. 2016

Meas. Sci. Technol.

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Flux linkage difference in the new joule balance can be obtained by the time integration of the induced voltage u(t) from the suspended coil relative to a moving magnet driven by a dc motor translation platform. Due to the finite acceleration of the dc motor, the transition and waveform of u(t) are finite and not regular. To accurately measure the time integration of u(t), a compensation waveform with precision time integration should be synthesized. In this paper, a stepwise compensation waveform is synthesized by a programmable Josephson voltage standard (PJVS) according to u(t). The accuracy of measuring the stepwise waveform with multiple transitions can be improved by reducing the ratio of the time integrated value of the total transitions to the total waveform less than one part in 102 in the joule balance. The time integration of the rise/fall transition is measured by a synchronized reference square wave generated by another PJVS system. With the total time integration more than 20 Vs, the uncertainty of the generated stepwise waveform is within 5.2 × 10−8 VsV−1s−1. The result confirms that the PJVS has the capability to generate a stepwise compensation voltage for flux linkage difference measurement.

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Coils and the Electromagnet Used in the Joule Balance at the NIM

Cited by 25 publications

References 18 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

External Magnetic Field Measurements in UME Kibble Balance

Stepwise compensation waveform generation by using Josephson voltage standards for joule balance

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