SI基本单位

根据2018年11月16日第26届国际计量大会包括中国在内53个成员国的集体表决,全票通过关于“修订国际单位制(SI)”的1号决议,国际单位制的7个基本单位:质量单位“千克”,电流单位“安培”,热力学温度单位“开尔文”,物质的量单位“摩尔”,时间单位“秒”、长度单位“米”,发光强度单位“坎德拉”全部改为由常数定义,此决议自2019年5月20日(世界计量日)起生效。此次变革是改变国际单位制采用实物基准的历史性变革,是人类科学发展进步中的一座里程碑。

全国科学技术名词审定委员会、计量学名词审定委员会组织业内专家,针对国际单位制的7个基本单位的定义进行了修订工作,现将其新修订的中文定义正式公布如下:

 

SI基本单位

新修订中文定义

国际公布英文定义

second

国际单位制中的时间单位,符号s。当铯频率ΔνCs,也就是铯133原子不受干扰的基态超精细跃迁频率,以单位Hz即s-1表示时,取其固定数值为9 192 631 770来定义秒。

The second, symbol s, is the SI unit of time. It is defined by taking the fixed numerical value of the caesium frequency ΔνCs 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.

metre

国际单位制中的长度单位,符号m。当真空中光速c以单位m/s表示时,取其固定数值为299 792 458来定义米,其中秒用ΔνCs定义。

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 ΔνCs.

千克

kilogram

国际单位制中的质量单位,符号kg。当普朗克常数h以单位J s即kg ms-1表示时,取其固定数值为6.626 070 15×10-34来定义千克,其中米和秒用c和ΔνCs定义。

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 ΔνCs.

安培

ampere

国际单位制中的电流单位,符号A。当基本电荷e以单位C即A s表示时,取其固定数值为1.602 176 634×10-19来定义安培,其中秒用ΔνCs定义。

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 ΔνCs.

开尔文

kelvin

国际单位制中的热力学温度单位,符号K。当玻尔兹曼常数k以单位J K-1即kg m2 s-2 K-1表示时,取其固定数值为1.380 649×10-23来定义开尔文,其中千克、米和秒用hc和ΔνCs定义。

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 ΔνCs.

摩尔

mole

国际单位制中的物质的量的单位,符号mol。1摩尔精确包含6.022 140 76×1023个基本单元。该数称为阿伏伽德罗数,为以单位mol-1表示的阿伏伽德罗常数NA的固定数值。

一个系统的物质的量,符号n,是该系统包含的特定基本单元数的量度。基本单元可以是原子、分子、离子、电子、其它任意粒子或粒子的特定组合。

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, NA, 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.

坎德拉

candela

国际单位制中的沿指定方向发光强度单位,符号cd。当频率为540×1012 Hz的单色辐射的光视效能Kcd以单位lmW-1即cd sr W-1或cd sr kg-1 m-2 s3表示时,取其固定数值为683来定义坎德拉,其中千克、米、秒分别用hc 和ΔνCs定义。

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, Kcd, 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 ΔνCs.

 

(英文定义源自:CGPM. 26th CGPM Resolution 1: On the revision of the International System of Units (SI). 2018-11-16[2019-5-5] )