1.52 | International System of Units, (SI) | ||

System of units, based on the International System of Quantities, their names and symbols, including a series of prefixes and their names and symbols, together with rules for their use, adopted by the General Conference on Weights and Measures (CGPM). | |||

Note 1: | The SI is founded on the seven base quantities of the ISQ and the terms and symbols of the corresponding base units that are contained in Table 1.2. | ||

Note 2: | The base units and the coherent derived units of the SI form a coherent set, designated the “set of coherent SI units”. | ||

Note 3: | For a full description and explanation of the International System of Units, see the current edition of the SI brochure published by the Bureau International des Poids et Mesures (BIPM)^{32 } and available on the BIPM website.^{33 } | ||

Note 4: | In quantity calculus, the quantity ‘number of entities’ is often considered to be a base quantity, with the base unit ‘one’, symbol ‘1’. | ||

Note 5: | SI prefixes for multiples of units and submultiples of units are given in Table 1.3. | ||

Note 6: | The SI prefixes given in Table 1.3 may be used for decimal multiples and decimal submultiples of SI base units and SI derived units only. The prefixes refer strictly to powers of 10 and should not be used for powers of 2 for which other prefixes apply. A non-decimal multiple of the SI base unit second is the hour. See: ref. 1 entry 1.17. | ||

Note 7: | From 20 May 2019, SI units are based on seven “defining constants” the numerical values of which are fixed.^{32 } The constants are: the hyperfine transition frequency of the caesium 133 atom, the speed of light in vacuum, the Planck constant, the elementary charge, the Boltzmann constant, the Avogadro constant, and the luminous efficacy of monochromatic radiation of frequency 540 × 10^{12} Hz. These constants are defined and so have no uncertainty. See Table 1.9. | ||

Source: [VIM 1.16] with added Notes 6 and 7. |

1.52 | International System of Units, (SI) | ||

System of units, based on the International System of Quantities, their names and symbols, including a series of prefixes and their names and symbols, together with rules for their use, adopted by the General Conference on Weights and Measures (CGPM). | |||

Note 1: | The SI is founded on the seven base quantities of the ISQ and the terms and symbols of the corresponding base units that are contained in Table 1.2. | ||

Note 2: | The base units and the coherent derived units of the SI form a coherent set, designated the “set of coherent SI units”. | ||

Note 3: | For a full description and explanation of the International System of Units, see the current edition of the SI brochure published by the Bureau International des Poids et Mesures (BIPM)^{32 } and available on the BIPM website.^{33 } | ||

Note 4: | In quantity calculus, the quantity ‘number of entities’ is often considered to be a base quantity, with the base unit ‘one’, symbol ‘1’. | ||

Note 5: | SI prefixes for multiples of units and submultiples of units are given in Table 1.3. | ||

Note 6: | The SI prefixes given in Table 1.3 may be used for decimal multiples and decimal submultiples of SI base units and SI derived units only. The prefixes refer strictly to powers of 10 and should not be used for powers of 2 for which other prefixes apply. A non-decimal multiple of the SI base unit second is the hour. See: ref. 1 entry 1.17. | ||

Note 7: | From 20 May 2019, SI units are based on seven “defining constants” the numerical values of which are fixed.^{32 } The constants are: the hyperfine transition frequency of the caesium 133 atom, the speed of light in vacuum, the Planck constant, the elementary charge, the Boltzmann constant, the Avogadro constant, and the luminous efficacy of monochromatic radiation of frequency 540 × 10^{12} Hz. These constants are defined and so have no uncertainty. See Table 1.9. | ||

Source: [VIM 1.16] with added Notes 6 and 7. |

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