This document has been composed to provide an authoritative reference on units used in Powertec documentation. The list of units and their definitions have been compiled with specific reference to NIST Special Publication 330 which forms the basis for the rules and style conventions for expressing values of quantities, along with ISO/IEC standards which covers units and quantities related to electromagnetism, electronics, and telecommunications.
- NIST Spec. Pub. 330, The International System of Units.[1]
- IEC 80000-6:2008, Quantities and Units, Part 6. Electromagnetism[2]
- IEC 60027-2:2005, Letter symbols to be used in electrical technology, Part 2: Telecommunications and Electronics[3]
- ISO 80000-3:2006, Quantities and units -- Part 3: Space and time[4]
- JEDEC Standard 100B.01, Terms, Definitions, and Letter Symbols ... Memory Integrated Circuits[5]
Rules & Style Conventions
The value of a quantity must always be expressed as the product of a number and a unit, whereby the number multiplying the unit is the numerical value of the quantity expressed in that unit. Symbols for units are treated as mathematical entities, this permits treatment by the ordinary rules of algebra - the equation of which follows: Quantity = Number * Unit.
Formatting
Powertec documentation must format units in accordance to the following rule set;
- Symbols for quantities are generally single letters set in italic font, which may be further qualified by information in subscript, superscript, or brackets.
- Unit symbol should not be used to provide specific information about the quantity. Units are never qualified by further information in subscript, superscript, or brackets.
- The numerical value must always preceed the unit.
- A single space is always used to separate the unit from the number, the space being regarded as a multiplication sign.
- Ranges must repeat the unit (e.g., 10 dB to 15 dB), dashes must not be used.
- Numerical values to be formatted in accordance to IEEE Standards Style Manual.
Unit Symbols & Definitions
| Symbol | Name | Quantity | Definition & Notes |
|---|---|---|---|
| A | ampere | electric current | The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 meter apart in vacuum, would produce between these conductors a force equal to 2 × 10−7 MKS unit of force [newton] per meter of length. |
| AWG | American Wire Gauge | wire diameter | Non-SI, wire gauge system, included due to commonality. Powertec documentation should use cross-sectional area where possible. |
| b | bit | digital information | IEEE 1541 recommended symbol for bit. Acronym for 'binary digit' which can have one out of two possible values, e.g. 0/1 or +1/-1 or low/high. |
| B | byte | digital information | Group of eight binary digits. |
| bit | bit | digital information | IEC 60027 recommended symbol for bit. Powertec documentation accepts usage of both, lower-case b is preferred. |
| bps | bits per second | data rate | Commonly used abbreviation instead of b/s. Unit prefixes apply, e.g. 1 Mbps = 1 Mb/s. |
| cm | centimeter | length | Unit of length. 1 cm = 0.01 m. Not recommended for use in Powertec documentation. |
| dB | decibel | logarithmic ratio | Logarithmic unit used to express the ratio of the value of that quantity to a reference value of the same quantity. One tenth of the bel (B): 1 B = 10 dB. |
| dBc | decibel carrier | logarithmic ratio | Power relative to known power of carrier c. |
| dBd | decibel dipole | logarithmic ratio | Forward gain of an antenna compared with a half-wave dipole antenna. 0 dBd = 2.15 dBi. Not recommended for use in Powertec documentation. |
| dBi | decibel isotropic | logarithmic ratio | Forward gain of an antenna compared with the hypothetical isotropic antenna. |
| dBm | decibel milliwatt | logarithmic ratio | Power relative to 1 milliwatt. |
| dBq | decibel quarterwave | logarithmic ratio | Forward gain of an antenna compared to a quarter wavelength whip. 0 dBq = −0.85 dBi. Not recommended for use in Powertec documentation. |
| dBV | decibel volt | logarithmic ratio | Voltage relative to 1 volt, regardless of impedance. |
| dBμV | decibel microvolt | logarithmic ratio | Voltage relative to 1 microvolt. |
| dBW | decibel watt | logarithmic ratio | Power relative to 1 watt. |
| °C | degree Celsius | Celsius temperature | °C = K + 273.16 |
| F | farad | capacitance | Equal to the capacitance of a capacitor in which one coulomb of charge causes a potential difference of one volt. |
| ft | foot | length | 1 ft = 0.3048 m. Not recommended for use in Powertec documentation. |
| g | gram | mass | 1 g = 0.001 kg. |
| GB | gigabyte | digital information | 1 GB = 109 B = 1 000 000 000 B. NOTE: See heading Unit Prefixes - Base-2 for deprecation of base-2 representation. |
| GHz | gigahertz | frequency | 1 GHz = 1 000 000 000 Hz. |
| GiB | gibibyte | digital information | 1 GiB = 230 B = 1 073 741 824 B. |
| h | hour | time | 1 h = 60 min = 3600 s. |
| Hz | hertz | frequency | Equal to one cycle per second. |
| J | joule | work | Equal to the work done by a force of one newton when its point of application moves one metre in the direction of action of the force. J = N m |
| K | kelvin | thermodynamic temperature | The fraction 1/273.16 of the thermodynamic temperature of the triple point of water. |
| kB | kilobyte | digital information | 1 kB = 103 B = 1000 B. NOTE: See heading Unit Prefixes - Base-2 for deprecation of base-2 representation. |
| kHz | kilohertz | frequency | 1 kHz = 1000 Hz. |
| KiB | kibibyte | digital information | 1 kiB = 210 B = 1024 B. |
| kg | kilogram | mass | Equal to the mass of the international prototype of the kilogram. |
| m | meter | length | Length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second. |
| MB | megabyte | digital information | 1 MB = 106 B = 1 000 000 B. NOTE: See heading Unit Prefixes - Base-2 for deprecation of base-2 representation. |
| MHz | megahertz | frequency | 1 MHz = 1 000 000 Hz. |
| MiB | mebibyte | digital information | 1 MiB = 220 B = 1 048 576 B. |
| min | minute | time | 1 min = 60 s. |
| mm | millimeter | length | 1 mm = 0.001 m. Included due to commonality within documentation. |
| ms | millisecond | time | 1 ms = 1/1000 s. Included due to commonality within documentation. |
| N | newton | force | It is equal to the force that would give a mass of one kilogram an acceleration of one metre per second per second. N = kg m s-2 |
| Ω | ohm | electrical resistance | The ohm is the electric resistance between two points of a conductor when a constant potential difference of 1 volt, applied to these points, produces in the conductor a current of 1 ampere, the conductor not being the seat of any electromotive force. |
| Pa | pascal | pressure | Unit of pressure or stress, equal to one newton per square metre. Pa = N m2 |
| pF | picofarad | capacitance | 1 pF = 10-12 F. |
| rad | radian | angular measure | Unit of measurement of angles equal to about 57.3°, equivalent to the angle subtended at the centre of a circle by an arc equal in length to the radius. |
| s | second | time | The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom. |
| Sv | sievert | dose equivalent | Unit of dose equivalent (biological effect of ionizing radiation). Equal to an effective dose of a joule of energy per kilogram of recipient mass. Sv = J/kg |
| V | volt | potential difference | Unit of potential difference and of electromotive force. The volt is the potential difference between two points of a conducting wire carrying a constant current of 1 ampere, when the power dissipated between these points is equal to 1 watt. |
| W | watt | power | The watt is the power which in one second gives rise to energy of 1 joule |
Unit Prefixes - Base-10
The prefix symbol table below is included to depict the accepted range of units used in Powertec documentation. Prefix symbols are are attached to unit symbols without a space between the prefix symbol and the unit symbol, for example 1000 watts may be represented as 1 kW, which is not explicitly noted in the unit symbols table above. Formatting of the unit prefixes is to follow conventions outlined in NIST documentation.
It should be noted that the below table is only applicable for quantities in base 10, and should not be referred to for quantities in base 2 such as in the context of digital information.
| Factor | Name | Symbol | Factor | Name | Symbol |
|---|---|---|---|---|---|
| 101 | deka | da | 10-1 | deci | d |
| 102 | hecto | h | 10-2 | centi | c |
| 103 | kilo | k | 10-3 | milli | m |
| 106 | mega | M | 10-6 | micro | μ |
| 109 | giga | G | 10-9 | nano | n |
| 1012 | tera | T | 10-12 | pico | p |
| 1015 | peta | P | 10-15 | femto | f |
| 1018 | exa | E | 10-18 | atto | a |
| 1021 | zetta | Z | 10-21 | zepto | z |
| 1024 | yotta | Y | 10-24 | yocto | y |
Unit Prefixes - Base-2
The use of base-10 prefixes such as kilo, mega, giga, etc. frequently leads to confusion in the context of binary or digital information, whereby 1 kilobit might be interpreted as either 1000 bits, or 1024 bits. To provide clarity on the matter, IEC 60027-2 has adopted prefixes for specifically base-2 quantities, to provide an alternative to the now deprecated use of kilo, mega, giga, etc. when referring to quantities in powers of two (i.e. in 1024n increments).
It is acknowledged that prefixes kilo, mega, giga, and others may continue to refer to base-2 quantities in common usage, however formal Powertec documentation is prohibited from using such prefixes, and instead must follow IEC 60027-2 when requiring base-2 binary multipliers.
| Factor | Name | Symbol | Multiplier Value |
|---|---|---|---|
| 210 | kibi | Ki | 1 Ki = 1 024 |
| 220 | mibi | Mi | 1 Mi = 1 048 576 |
| 230 | gibi | Gi | 1 Gi = 1 073 741 824 |
| 240 | tebi | Ti | 1 Ti = 1 099 511 627 776 |
References
- NIST, “THE INTERNATIONAL SYSTEM OF UNITS (SI),” Natl. Inst. Stand. Technol., Gaithersburg, MD, Spec. Pub 330, 2008 Ed., Mar. 2008.
- IEC TC 25, "IEC 80000-6:2008 Quantities and Units -- Part 6. Electromagnetism", Intl. Electr. Comm., Geneva, Switzerland, ICS 01.040.29; 17.220.01, Mar. 2008.
- IEC TC 25, "IEC 60027-2:2005 Letter symbols to be used in electrical technology - Part 2: Telecommunications and electronics", Intl. Electr. Comm., Geneva, Switzerland, 25/298/FDIS, Aug. 2005.
- ISO TC 12, "ISO 80000-3:2006 Quantities and units -- Part 3: Space and time", Intl. Org. Std., Stockholm, Sweden, ICS 01.060; 90.92, Mar. 2006.
- JEDEC JC-10, "JESD100B.01 Terms, Definitions, and Letter Symbols for Microcomputers, Microprocessors, and Memory Integrated Circuits". JEDEC Sol. St. Tech. Assc., Arlington, VA, JESD100B.01, Dec. 2002.