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

Li, Zhengkun; Zhang, Zhonghua; He, Qing; Han, Bing; Lu, Yunfeng; Xu, Jinxin; Li, Shisong; Li, Chen; Wang, Gang; Zeng, Tao; Bai, Yang

doi:10.1109/tim.2015.2395552

Cited by 12 publications

(3 citation statements)

References 12 publications

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“…(2) The moving range in NIM-2 is five times longer than that in NIM-1. With the magnetic damping device and the active control vibration isolation base mentioned in [20], the error caused by the position instability can be reduced to 5 × 10 −8 .…”

Section: Discussionmentioning

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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Section: Discussionmentioning

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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“…When a relative displacement between the two coils is generated, the mechanical potential energy is measured in comparison to electromagnetic energy in the two coils. The principle of joule balance is shown in equation (1) [14][15][16][17].…”

Section: Position Locking Requirement For Joule Balance Nim-2mentioning

confidence: 99%

Stability improvement for coil position locking of joule balance

Bai

Liu

et al. 2017

Metrologia

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The relative vertical position locking precision between the exciting and suspended coils is an important uncertainty for the Planck constant traceability in joule balance. In order to improve the relative vertical position locking precision, several stability experiments are conducted. The stability characteristics of the suspended and exciting coils are measured using a six-axis laser interferometer system; meanwhile, the effectiveness of the active vibration isolation table is measured using a vibration measurement sensor. The piezoelectric ceramic actuators with PID controller are used to compensate the relative vertical displacement drifts while a six-axis laser interferometer system is used to measure the positions of two coils. Experimental results show that the relative vertical position is stably locked.

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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%

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

Cited by 12 publications

References 12 publications

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

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

Stability improvement for coil position locking of joule balance

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

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