– the intergovernmental organization through which Member States act together
     on matters related to measurement science and measurement standards.
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Present status

Since 2005 the BIPM has been developing a Kibble balance as a means for the practical realization of the expected new definition of the kilogram in terms of the Planck constant. The BIPM Kibble balance operates using a 0.5 T radial magnetic field, a 250 mm diameter and 1100 turn induction coil, a flowing current of ±13 mA and a test mass of 1 kg. Coil velocity is about 1 mm s–1 with typical excursion of 20 mm.

The apparatus is fully operational in air and in vacuum. The relative type B uncertainty on the Planck constant determination is currently about 2 x 10–7. The type B uncertainty is dominated by the residual misalignment of the interferometer laser beam due to the limited mechanical stability of the interferometer mount. A novel interferometer mounted on a much more stable support is being designed with the objective to reduce the uncertainty within 1 x 10–7. The standard deviation on the mean value for one week of measurements is a few parts in 108.



For further details see:

  1.  H. Fang, F. Bielsa, A. Kiss, T. Lavergne, Y. F. Lu, L. Robertsson, E. de Mirandés, S. Solve and M. Stock, Progress on the BIPM watt balance, Proc. CPEM 2016, 2016.
  2.  H. Fang, F. Bielsa, S. Li, A. Kiss, and M. Stock, The BIPM Kibble Balance for the realization of the redefined kilogram, Proc. CPEM 2018, 2018.