Amendment of the Weights and Measures Act 19852
1
Schedule 1 to the Weights and Measures Act 1985 (definitions of units of measurement) is amended as follows.
2
In Part 1 (measurement of length), in the second column of the table headed “metric units”, for the definition of “METRE” substitute—
for which the symbol “m” is used, is the SI2 unit of length, defined by taking the fixed numerical value of the speed of light in vacuum c to be 299 792 458 when expressed in the unit m/s, where the second is defined by taking the fixed numerical value of the caesium frequency ΔvCs, the unperturbed ground-state hyperfine transition frequency of the caesium 133 atom, to be 9 192 631 770 when expressed in the unit Hz, which is equal to s-1.
3
In Part 5 (measurement of mass or weight), in the second column of the table headed “metric units”, for the definition of “KILOGRAM” substitute—
for which the symbol “kg” is used, is the SI unit of mass, defined by taking the fixed numerical value of the Planck constant h to be 6.626 070 15 x 10-34 when expressed in the unit J s, which is equal to kg m2 s-1, where the second is defined by taking the fixed numerical value of the caesium frequency ΔvCs, the unperturbed ground-state hyperfine transition frequency of the caesium 133 atom, to be 9 192 631 770 when expressed in the unit Hz, which is equal to s-1.