Statutory Instruments
2019 No. 1211
Weights And Measures
The Weights and Measures Act 1985 (Amendment) and Units of Measurement Regulations 1986 (Amendment) Regulations 2019
Made
3rd September 2019
Laid before Parliament
4th September 2019
Coming into force
13th June 2020
The Secretary of State makes the following Regulations in exercise of the powers conferred by section 2(2) of the European Communities Act 1972( 1 ).
The Secretary of State is a Minister designated( 2 ) for the purposes of section 2(2) of that Act in relation to units of measurement to be used for economic, health, safety, or administrative purposes.
Citation and commencement
1. These Regulations—
(a) may be cited as the Weights and Measures Act 1985 (Amendment) and Units of Measurement Regulations 1986 (Amendment) Regulations 2019; and
(b) come into force on 13th June 2020.
Amendment of the Weights and Measures Act 1985
2. In the third column of the table in Part 7 of Schedule 1 to the Weights and Measures Act 1985( 3 ) (definitions of units of measurement of electricity)—
(a) for the definition given for “AMPERE” substitute—
“ for which the symbol “A” is used, is the SI unit of electric current, defined by taking the fixed numerical value of the elementary charge e to be 1.602 176 634 × 10 -19 when expressed in the unit C, which is equal to A 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 . ” ;
(b) in the definition given for “WATT”, after “joule”, insert “, where the second has the meaning given in the definition of “AMPERE””.
Amendment of the Units of Measurement Regulations 1986
3. For paragraph 1 of Schedule 1 to the Units of Measurement Regulations 1986( 4 ) (definitions of SI base units( 5 )) substitute—
“ SI base units.
| Quantity | Unit | |
|---|---|---|
| Name | Symbol | |
Definitions of SI base units Unit of time The second, symbol s, is the SI unit of time. It 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 . Unit of length The metre, symbol m, is the SI unit of length. It is 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 in terms of Δ v Cs . Unit of mass The kilogram, symbol kg, is the SI unit of mass. It is defined by taking the fixed numerical value of the Planck constant h to be 6.626 070 15 × 10 -34 when expressed in the unit J s, which is equal to kg m 2 s -1 , where the metre and the second are defined in terms of c and Δ v Cs . Unit of electric current The ampere, symbol A, is the SI unit of electric current. It is defined by taking the fixed numerical value of the elementary charge e to be 1.602 176 634 × 10 -19 when expressed in the unit C, which is equal to A s, where the second is defined in terms of Δ v Cs . Unit of thermodynamic temperature The kelvin, symbol K, is the SI unit of thermodynamic temperature. It is defined by taking the fixed numerical value of the Boltzmann constant k to be 1.380 649 × 10 -23 when expressed in the unit J K -1 , which is equal to kg m 2 s -2 K -1 , where the kilogram, metre and second are defined in terms of h , c and Δ v Cs . Unit of amount of substance The mole, symbol mol, is the SI unit of amount of substance. One mole contains exactly 6.022 140 76 × 10 23 elementary entities. This number is the fixed numerical value of the Avogadro constant, N A , when expressed in the unit mol -1 and is called the Avogadro number. The amount of substance, symbol n , of a system is a measure of the number of specified elementary entities. An elementary entity may be an atom, a molecule, an ion, an electron, any other particle or specified group of particles. Unit of luminous intensity The candela, symbol cd, is the SI unit of luminous intensity in a given direction. It is defined by taking the fixed numerical value of the luminous efficacy of monochromatic radiation of frequency 540 × 10 12 Hz, K cd , to be 683 when expressed in the unit lm W -1 , which is equal to cd sr W -1 , or cd sr kg -1 m -2 s 3 , where the kilogram, metre and second are defined in terms of h , c and Δ v Cs. | ||
| Time | second | s |
| Length | metre | m |
| Mass | kilogram | kg |
| Electric current | ampere | A |
| Thermodynamic temperature | kelvin | K |
| Amount of substance | mole | mol |
| Luminous intensity | candela | cd |
Special name and symbol of the SI derived unit of temperature for expressing Celsius temperature
| Quantity | Unit | |
|---|---|---|
| Name | Symbol | |
| Celsius temperature t is defined as the difference t = T – T 0 between the two thermodynamic temperatures T and T 0 where T 0 = 273.15 K. An interval or difference of temperature may be expressed either in kelvins or in degrees Celsius. The unit “degree Celsius” is equal to the unit “kelvin”. ” . | ||
| Celsius temperature | degree Celsius | °C |
Kelly Tolhurst
Parliamentary Under Secretary of State
Department for Business, Energy and Industrial Strategy
3rd September 2019
1972 c.68 . Section 2(2) was amended by section 27(1) of the Legislative and Regulatory Reform Act 2006 (c.51) and by Part 1 of the Schedule to the European Union (Amendment) Act 2008 (c.7) . It is prospectively repealed by section 1 of the European Union (Withdrawal) Act 2018 (c.16) , with effect from exit day (see section 20 of that Act).
S.I. 1976/897 , to which there are amendments not relevant to these Regulations.
S.I. 1986/1082 . Paragraph 1 of Schedule 1 was amended by S.I. 2001/55 to amend the definition of Celsius temperature and by S.I. 2009/3046 to update the definition of Kelvin and to adjust the italic heading of the definition of Celsius temperature.
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. 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.