Notice of the making of this Statutory Instrument was published in

“Iris Oifigiúil” of 5th May, 2020.

I, HEATHER HUMPHREYS, Minister for Business, Enterprise and Innovation, in exercise of the powers conferred on me by section 3 of the European Communities Act 1972 (No. 27 of 1972) and for the purpose of giving effect to Council Directive 80/181/EEC of 20 December 1979¹ as last amended by Directive 2019/1258/EU of the European Parliament and of the Council of 23 July 2019² , hereby make the following Regulations:

Citation and Commencement

1. (1) These Regulations may be cited as the European Communities (Units of Measurement) (Amendment) Regulations 2020.

(2) These Regulations come into operation on 13 June 2020.

Interpretation

2. In these Regulations—

“Principal Regulations” means the European Communities (Units of Measurement) Regulation 1992 ( S.I. No. 255 of 1992 );

3. Section 1.1 of Schedule 1 of the Principal Regulations is replaced by the following—

‘1.1. SI base units

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 C_s, 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 C_s.

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 m² s^{– 1}, where the metre and the second are defined in terms of c and Δ_v C_s.

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 C_s.

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 m² s^{– 2} K^{– 1}, where the kilogram, metre and second are defined in terms of h, c and Δ_v C_s.

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 * 10²³ 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 * 10¹² 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} s³, where the kilogram, metre and second are defined in terms of h, c and Δ_v C_s.

1.1.1. Special name and symbol of the SI derived unit of temperature for expressing Celsius temperature

Celsius temperature t is defined as the difference t = T – T₀ between the two thermodynamic temperatures T and T₀ where T₀ = 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”.’

GIVEN under my Official Seal,

01 May, 2020.

HEATHER HUMPHREYS,

Minister for Business, Enterprise and Innovation.

EXPLANATORY NOTE

(This note is not part of the Instrument and does not purport to be a legal interpretation.)

These Regulations are made to give effect to Council Directive No. 2019/1258/EU of the European Parliament and of the Council of 23 July 2019 on the approximation of the laws of Member States relating to units of measurement.

The main changes in the Regulations provide for new definitions of the SI base units. The new definitions are based on the new principle of fixed numerical values of the defining constants and are expected to improve the long-term stability and reliability of the SI base units as well as the accuracy and clarity of measurements.

1 Council Directive 80/181/EEC of 20 December 1979 on the approximation of the laws of the Member States relating to units of measurement and on the repeal of Directive 71/354/EEC (OJ L 39, 15.2.1980, p. 40)

2 OJ L 196, 24.7.2019, p. 6–9