Statutory Instruments
2020 No. 586
Weights And Measures
The Weights and Measures Act 1985 (Definitions of “Metre” and “Kilogram”) (Amendment) Order 2020
Made
9th June 2020
Coming into force
13th June 2020
The Secretary of State makes the following Order in exercise of the powers conferred by section 1(3) of the Weights and Measures Act 1985( 1 ).
In accordance with section 86(2) of that Act, the Secretary of State has consulted such organisations as appear to him to be representative of interests substantially affected by the Order.
In accordance with section 86(5) of that Act, a draft of the instrument was laid before Parliament and approved by a resolution of each House of Parliament.
Citation and commencement
1. This Order—
(a) may be cited as the Weights and Measures Act 1985 (Definitions of “Metre” and “Kilogram”) (Amendment) Order 2020; and
(b) comes into force on 13th June 2020.
Amendment of the Weights and Measures Act 1985
2. —(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 SI ( 2 ) 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 Δ v Cs , 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 m 2 s -1 , where the second is defined by taking the fixed numerical value of the caesium frequency Δ v Cs , 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 . ” .
Paul Scully
Parliamentary Under Secretary of State
Department for Business, Energy and Industrial Strategy
9th June 2020
The term “SI” refers to the International System of Units (“the SI”) adopted by the eleventh meeting of the General Conference on Weights and Measures in 1960 which is updated and amended from time to time. See The International System of Units (9th edition (2019)) edited by the International Bureau of Weights and Measures, Pavillon de Breteuil, F-92312 Sèvres Cedex France, ISBN 978-92-822-2272-0.