Correct use of abbreviations

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1

I find myself wondering from time to time what is the correct way to type things like microseconds - is it µS or µs? Is milliamp mA or ma? Is volt V or v?

If you check out International System of Units - Wikipedia you can find various definitions.

Simplified summary for forum users

I will keep the explanation below relevant to electronics, and not cover things like luminosity, moles etc.

Basic Units

  • Length: meter - Symbol: m
  • Mass: kilogram - Symbol: kg
  • Time: second - symbol: s
  • Electric current: ampere - symbol: A

Derived Units

  • Frequency: hertz - Symbol: Hz
  • Energy: joule - Symbol: J
  • Power: watt - Symbol: W
  • Temperature: celsius - Symbol: °C
  • Charge: coulomb - Symbol: C
  • Potential: volt - Symbol: V
  • Resistance: ohm - Symbol: Ω
  • Conductance: siemens - Symbol: S
  • Capacitance: farad - Symbol: F
  • Inductance: henry - Symbol: H

Units prefixes

  • Tera: 1012 - Symbol: T
  • Giga: 109 - Symbol: G
  • Mega: 106 - Symbol: M
  • Kilo: 103 - Symbol: k
  • milli: 10-3 - Symbol: m
  • micro: 10-6 - Symbol: µ
  • nano: 10-9 - Symbol: n
  • pico: 10-12 - Symbol: p

Binary prefixes for bytes

Not part of SI, but commonly accepted in computing.

  • Kilobyte: 210 (1,024)- Symbol: KB
  • Megabyte: 220 (1,048,576)- Symbol: MB
  • Gigabyte: 230 (1,073,741,824) - Symbol: GB
  • Terabyte: 240 (1,099,511,627,776) - Symbol: TB

Writing symbols

  • Values are written as a quantity, followed by a space, followed by the units. eg. 2.21 kg, not 2.21kg
  • Prefixes are part of the unit, and written without a space. eg. kHz not k Hz
  • Symbols do not have a plural form. eg. 2 km not 2 kms
  • You cannot interchange upper and lower-case. eg. 1 mW and 1 MW are two very different quantities.
2

See:

I must admit, I can be careless.

3

A nice reference. I was attempting to summarize in one page, but that is useful if you are going for more obscure things. :slight_smile:

I must admit I can be careless.

Me too. What I wrote above does not imply my own writings are not littered with errors, but I will try harder in the future. :wink:

4

Ditto

5

LarryD:
See:
Electronic and Engineering Abbreviations and Acronyms

I must admit, I can be careless.

is this right?

  • kohm - kilohm

I would expect kiloohm (double oo)

6

Commonly used multiples and submultiples in electrical and electronic usage are the microohm, milliohm, kilohm, megohm, and gigaohm, the term "gigohm", though not official, is in common use for the latter.

7

I try to be correct - except that I use u instead of the µ symbol. How do you get a µ with the keyboard.?

I have just copied and pasted it here

...R

8

On Ubuntu I set up RH-Alt as the "Compose" key and then type RH-Alt, followed by "m" "u" to do it. On the Mac I can hold down Option and type "m" for the same effect. Under Windows I'm not sure.

9

Windows : ALT-0181 (do not forget the 0)

10

Thanks Nick.

On my Puppy Linux (derived from Ubuntu) RH-Alt m works

...R

11

Windoze: Alt-230

Linux: Use the Character Map, "Latin-1 Supplement". It remembers the last character you requested.