Help:ISO 31-0
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As much as possible, I would like the values and units used in EEWiki to conform to the International ISO 31 standards, notably Part 0 General Principles, Third Edition 1992-08-01[1].
The units include the SI[2] base units[3], supplementary units[4] and derived units [5] are permissible.
The standard SI prefixes from 10-24 to 1024[6] shall be used to designate multipliers.
The symbols ppm, ppb and ppt are prohibited in the ISO standard but may be used here for convenience and easy understanding. Other permissible units are the minute (min), hour (h), day (d), degree (°), angular minute ('), angular second ("), litre (l), tonne (t), electronvolt (eV) and unified atomic mass unit (u).
International unit symbols shall be used in upright (not italic) characters, never in the plural and without a full stop (except at the end of a sentence. All symbols shall be in lower case except where they are derived from the name of a person or place.[7] A space shall always be placed between the value and the unit[8], except for angular °, ' and ", which shall juxtapose the value (note that °C for temperature does have a space!). Names of units spelt out in full shall be always in lower case, without diacritical marks, e.g. siemens, ampere etc. Where compound units are multiplied or divided,, the multiplier sign is a dot (.) and the divider sign is a slash (/). Exponents should use the <sup></sup> syntax. To symbolise metres per second, for example, either m/s or m.s-1 is permissible.
Numeric values shall use the comma (,) or full stop (.) as the decimal divider. The decimal divider shall always be preceded by at least one digit, a zero (0), if the value is less than unity[9]. The multiplier for numbers is x, not . ( the half-high dot is permissible but not practical with ordinary keyboards). The thousand divider should always be a fixed space, never a dot or a comma, in three digits from the decimal divider.[10] A space shall always be placed before and after mathematical symbols, such as +, -, x, /, ± etc.
The following table gives some examples for guidance:
| Wrong | Right |
| 12m | 12 m |
| 100°C | 100 °C |
| 273,15 °K | 273,15 K |
| 15 ° 30 ' 20 " | 15° 30' 20" |
| 100 µµF | 100 pF |
| l=12 m-7 m | l = 12 m - 7 m |
| l = 12 - 7 m | l = 12 m - 7 m |
| t = 28,4 ± 0,2 °C | t = 28,4 °C ± 0,2 °C t = (28,4 ± 0,2) °C |
| π=3.14159265 | π = 3.141 592 65 |
| v = .35 L | v = 0.35 l |
| 35 lb (15.88 kg) | 15.88 kg (35 lb) |
| 12,000,000 | 12 000 000 |
| 9,5L/100km | 9,5 l/100 km |
| 120 kph | 120 km/h |
| λ = 220 x (1 ± 0,02) W/m.K | λ = 220 x (1 ± 0,02) W/(m.K) |
References
- ↑ International Standards Organisation ISO 31-0:1992(E)
- ↑ Système International d'Unités, 11e Conférence Générale des Poids et Mésures, CGPM 1960
- ↑ ISO 31-0 Table 1
- ↑ ibid, para 2.3.2.2
- ↑ ibid, Tables 2 and 3
- ↑ ibid, Table 4
- ↑ ibid, Section 3.2
- ↑ ibid, para. 3.4
- ↑ ibid, para. 3.3.2
- ↑ ibid, para. 3.3.1
