Progress on the BIPM Watt Balance

Fang, Hao; Bielsa, Franck; Kiss, A.; Lavergne, T.; Lu, Yunfeng; Robertsson, L.; Mirandes, E. de; Solve, S; Stöck, M

doi:10.1109/tim.2008.2009913

Cited by 26 publications

(20 citation statements)

References 6 publications

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“…The first results obtained with this particular measurement method are in agreement with the traditional two modes method [1]. As a consequence, in the present configuration of the apparatus, the voltage across the moving coil comprises two components: 0.6 V is produced as a consequence of the 1 mA current flow through the coil and an induced voltage resulting from the movement of the coil in the magnetic field that reaches the maximum value of ±0.1 V at the constant velocity of ±0.2 mm/s (cf.…”

Section: Introductionsupporting

confidence: 74%

A bias source for the voltage reference of the BIPM watt balance

Solve

Chayramy

Picard

et al. 2012

2012 Conference on Precision Electromagnetic Measurements

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We have developed a programmable current bias source to set the voltage output of a Josephson Voltage Standard that will be operated on the watt balance experiment. The device has been designed to bias separately all of the 13 independent segments of the Josephson array in order to be able to track the induced voltage across the moving coil during the constant velocity and acceleration phases. It is powered from Lithium-ion batteries in order to avoid electrical offsets originating from ground loops and to allow long series of measurements.Index Terms -Programmable Bias Current source, Josephson Voltage Standard, watt balance experiment.

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Section: Introductionsupporting

confidence: 74%

A bias source for the voltage reference of the BIPM watt balance

Solve

Chayramy

Picard

et al. 2012

2012 Conference on Precision Electromagnetic Measurements

Self Cite

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“…In the revised SI, the kilogram, the last base unit of the SI that is still based on an artefact, will be redefined by fixing the numerical value of the Planck constant [2]. Over the last few decades, several national metrology institutes (NMIs) across the world have been working hard relating the kilogram to the Planck constant h by means of either the Kibble balance [3][4][5][6][7][8][9][10][11][12] or the x-ray crystal density (XRCD) method [13]. The Kibble balance, which was proposed by Kibble in 1975 [14], has been adopted by the majority of NMIs.…”

Section: Introductionmentioning

confidence: 99%

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

Xu¹,

You²,

Li³

et al. 2018

Metrologia

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The first determination of the Planck constant with the second generation of the joule balance, NIM-2, was completed in 2017 with an uncertainty of 2.4 × 10 −7 . Due to the movement of the magnet during the measurement process, the effect of the external field is a critical problem in NIM-2. At present, the electromagnet system is used in NIM-2. By taking the average of the results with positive and negative exciting currents, the uncertainty from the external field is reduced to 1.7 × 10 −7 , which is still the largest source in the uncertainty budget as all the other items are less than 1 × 10 −7 . In the near future, a permanent magnet system will be applied in NIM-2 and the main field cannot be reversed. Although the coupling of the external magnetic field in the permanent magnet system is about 40 times less than that in the electromagnet system, further reduction of this effect is still required in the permanent magnet system. In this paper, the effect of the external field is analyzed in both an electromagnet system and a permanent magnet system based on simulations and experiments. Then, the methods of magnetic shielding and compensation coils are proposed and simulated in the permanent magnet system. The results show that it may be possible to reduce the uncertainty of the external field to less than 2 × 10 −8 in the permanent magnet system by employing the two methods.

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“…An overlapped-flexure shown in figure 7 has been built to replace the former flexures [11]. The overlapped-flexure can help to achieve the force application points of electromagnetic and gravitational force coinciding [12,13]. Then, the timeconsuming adjustment process of the test pan is not necessary.…”

Section: The New Suspension Systemmentioning

confidence: 99%

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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Progress on the BIPM Watt Balance

Cited by 26 publications

References 6 publications

A bias source for the voltage reference of the BIPM watt balance

A bias source for the voltage reference of the BIPM watt balance

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

The upgrade of NIM-2 joule balance since 2017

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