Abstract

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.

Highlights

  • The redefinition of the kilogram unit, approved at the 26th meeting of The General Conference on Weights and Measures (CGPM), held in November 2018, has replaced its previous artefact definition via the mass of the International Prototype of the Kilogram (IPK) with one based on the fixed numerical value of the Planck constant [1], [2]

  • Extensive studies have been performed at several national metrology institutes (NMIs) across the world to ensure a smooth transition to the revised definition of the kilogram

  • Devised at the National Physical Laboratory (NPL) by Brian Kibble in 1975 [30], [31], the Kibble balance relates mechanical and electrical powers where the electrical power is measured in terms of Planck’s constant by using two macroscopic quantum phenomena known as the quantum Hall effect [32] and the Josephson effect [33] to link the macroscopic mass to the Planck constant

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Summary

INTRODUCTION

The redefinition of the kilogram unit, approved at the 26th meeting of The General Conference on Weights and Measures (CGPM), held in November 2018, has replaced its previous artefact definition via the mass of the International Prototype of the Kilogram (IPK) with one based on the fixed numerical value of the Planck constant [1], [2]. Aside from its distinctive properties, there is an important difference between the UME Kibble balance and traditional twophase, moving coil Kibble balances in that the external magnetic field introduces an asymmetry between the Ampere’s law of force and Faraday’s law of induction. In moving magnet Kibble balance experiments, there occurs an asymmetry between Ampere’s law of force and Faraday’s law of induction due to the external magnetic field.

Ampere’s Law of Force
Faraday’s Law of Induction
EXTERNAL MAGNETIC FORCE MEASUREMENTS
Stability of External Magnetic Flux Difference
Non-linear Effects
MONITORING THE CHANGE IN MAGNETIC FLUX DENSITY
CONCLUSION

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