In November 2018, the 26th General Conference on Weights and Measures (CGPM) will review the International System of Units (SI) of four of the seven base units namely kilogram, ampere, kelvin and mole by fixing the values of the Planck constant (h), the elementary charge (e), the Boltzmann constant (k) and the Avogadro constant (NA). Upon approval, the redefined SI will be implemented worldwide on the following World Metrology Day which is on May 20 2019.

The SCL as an observer of the Consultative Committee for Electricity and Magnetism (CCEM) attended its 30th meeting in March 22-24 2017. Consultative Committees bring together the world's renowned experts and scientists from top national metrology institutes (NMIs) to advise the International Committee for Weights and Measures (CIPM) on scientific and technical matters related to the respective fields in metrology. To prepare for the redefinition of SI, the CCEM meeting has discussed the impact of the proposed redefined SI on the Electricity and Magnetism (EM) metrology and prepared guidelines for its implementation.

Currently, the definition of ampere, the SI base unit for Electricity, is realised by Ohm’s law which is based on the practical realisations of the SI derived units of the volt and the ohm. The new proposed definition of the ampere is by fixing the values of the elementary charge, which is equal to ampere second (C = A s). With the new proposed definition, the realisation and dissemination of electrical units can be fully coherent with the SI. The SCL will update the testing and certification industry in Hong Kong on the latest development.