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This is a list of units that are not defined as part of the International System of Units (SI), but are otherwise mentioned in the SI,[1][2] because either the General Conference on Weights and Measures (CGPM) accepts their use as being multiples or submultiples of SI-units, they have important contemporary application worldwide, or are otherwise commonly encountered worldwide.
Units officially accepted for use with the SI
| Name | Symbol | Quantity | Equivalent SI unit |
|---|---|---|---|
| Widely used units expected to be used indefinitely | |||
| minute | min | time (SI unit multiple) | 1 min = 60 s |
| hour | h | time (SI unit multiple) | 1 h = 60 min = 3600 s |
| day | d | time (SI unit multiple) | 1 d = 24 h = 1440 min = 86400 s |
| degree | ° | plane angle (dimensionless unit) | 1° = (π / 180) rad |
| minute | ′ | plane angle (dimensionless unit) | 1′ = (1 / 60)° = (π / 10800) rad |
| second | ″ | plane angle (dimensionless unit) | 1″ = (1 / 60)′ = (1 / 3600)° = (π / 648000) rad |
| hectare | ha | area (decimal unit multiple) | 1 ha = 100 a = 10000 m2 = 1 hm2 |
| litre | l or L | volume (decimal unit multiple) | 1 L = 1 dm3 = 0.001 m3 = 1000 cc = 1000 cm3 |
| tonne | t | mass (decimal unit multiple) | 1 t = 103 kg = 1 Mg |
| Logarithmic units | |||
| neper | Np | level of a field quantity | LF = ln(F / F0) Np |
| level of a power quantity | LP = 1⁄2 ln(P / P0) Np | ||
| bel, decibel | B, dB | level of a field quantity | LF = 2 log10(F / F0) B |
| level of a power quantity | LP = log10(P / P0) B | ||
| Units with experimentally determined values | |||
| electronvolt | eV | energy | 1 eV = 1.60217653(14)×10−19 J |
| unified atomic mass unit dalton |
u Da |
mass | 1 u = 1 Da = 1.66053886(28)×10−27 kg |
| astronomical unit | ua[3][4][5] | length | 1 ua = 1.49597870691(6)×1011 米 |
| Natural units (n.u.) | |||
| n.u. of speed (speed of light in vacuum) | c0 | speed | 299792458 m/s (exact)[6] |
| n.u. of action (reduced Planck constant) | ħ | action | 1.05457168(18)×10−34 J·s |
| n.u. of mass (electron mass) | me | mass | 9.1093826(16)×10−31 kg |
| n.u. of time | ħ / mec02 | time | 1.2880886677(86)×10−21 s |
| Atomic units (a.u.) | |||
| a.u. of charge (elementary charge) | e | electric charge | 1.60217653(14)×10−19 C |
| a.u. of mass (electron mass) | me | mass | 9.1093826(16)×10−31 kg |
| a.u. of action (reduced Planck constant) | ħ | action | 1.05457168(18)×10−34 J·s |
| a.u. of length, bohr (Bohr radius) | a0 | length | 0.5291772108(18)×10−10 米 |
| a.u. of energy, hartree (Hartree energy) | Eh | energy | 4.35974417(75)×10−18 J |
| a.u. of time | ħ / Eh | time | 2.418884326505(16)×10−17 s |
Common units not officially sanctioned
| Name | Symbol | Quantity | Equivalent SI unit |
|---|---|---|---|
| ångström, angstrom | Å | length | 1 Å = 0.1 nm = 10−10 m |
| are | a | area | 1 a = 1 dam2 = 100 m2 |
| barn | b | area | 1 b = 10−28 m2 |
| bar | bar | pressure | 1 bar = 105 Pa |
| millibar | mbar | pressure | 1 mbar = 1 hPa = 100 Pa |
| atmosphere | atm | pressure | 1 atm = 1013.25 mbar = 1013.25 hPa = 101325 Pa exactly (commonly used in atmospheric meteorology, in oceanography and for pressures within liquids, or in the industry for pressures within containers of liquefied gas) |
| dyne per square centimetre (barye) | Ba | pressure | 1 Ba = 0.1 Pa = 0.1 N/m2 = 100 g·cm−1·s−2 |
| millimetre of mercury | mmHg | pressure | 1 mmHg = 133.322387415 Pa at 0 °C = 133.322387415 N/m2 at 0 °C = 133.322387415 kg·cm−1·s−2 at 0 °C |
| torr | Torr | pressure | 1 Torr = 1/760 atm = 133.322368421... Pa = 133.322368421... N/m2 = 133.322368421... kg·cm−1·s−2 |
参见
References
- ^ Non-SI units accepted for use with the SI, and units based on fundamental constants (PDF). SI brochure (8th edition). BIPM. [2010-08-28].
- ^ Taylor, Barry N. (ed.). The International System of Units (SI) (PDF). Special Publication 330. Gaithersburg, Maryland: National Institute of Standards and Technology (NIST). 2001.
- ^ International Bureau of Weights and Measures, The International System of Units (SI) (PDF) 8th: 126, 2006, ISBN 92-822-2213-6 （英语）
- ^ ISO 80000-3
- ^ The IAU Style Manual (1989): The Preparation of Astronomical Papers and Reports (PDF): 23
- ^ In this case it is not the speed of light, but the length of the metre that is obtained by experiment
