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Subject:Re: 50-ohm vs. # symbol From:Bonnie Nestor <mnj -at- ORNL -dot- GOV> Date:Mon, 14 Aug 1995 13:28:49 -0400
Well, darn. I replied to the original poster via e-mail, but Rick
Lippincott has just rung my bell in his response to Dan Voss (hi, Dan!):
> Our own usage suggests the proper answer to the original question
> should have been "None of the above." The convention we all seem to
> be following is:
> (Numeral)(Symbol)
> Which would imply the correct answer to the original question would be:
> 50[uom] resistor
> No hyphen, no space.
> And no rule to back up the theory....
You want a rule, I've got a rule. The ASTM Standard for Metric Practice,
E380-86 (or, for the up-to-date, E380-92, I think), from the American
Society for Testing and Materials, says and I quote (using the notation
"^o" to represent a degree sign):
3.5.1.5 When a quantity is expressed as a numerical value and a unit
symbol, a space should be left between them. For example, use 35 mm, _not_
35mm, and 2.37 lm (for 2.37 lumens), _not_ 2.37lm.
_Exception:_ No space is left between the numerical value and the symbols
for degree, minute, and second of plane angle, and degree Celsius. For
example, use 45^o, 25^oC.
3.5.1.6 When a quantity expressed as a number and a unit is used in an
adjectival sense, it is preferable to use a hyphen instead of a space
between the number and the unit name or between the number and the symbol.
Examples: a three-metre pole...The length is 3 m...A 35-mm film...The
width is 35 mm. However, per 3.5.1.5 Exception, a 90^o angle...an angle of
90^o.
[END QUOTE]
There it is: between the number and the unit name or between the number
and the symbol. So if it's a unit modifier, it doesn't matter whether it's
a 100-watt bulb or a 100-W bulb -- it's still "preferable" to use a
hyphen.
(By the way, bringing up the use of "K" to indicate file size isn't really
fair, because "K" is a nonstandard abbreviation for thousand -- not a unit
name. But that's a whole 'nother argument...)
Bonnie Nestor
mnj -at- ornl -dot- gov
DISCLAIMER: I work at Oak Ridge National Laboratory, for Lockheed Martin Energy
Systems, which is under contract to the U.S. Department of Energy -- but I
don't speak for any of them, and they return the favor.
