
Unit Definitions - btilly
https://futureboy.us/frinkdata/units.txt
======
stygiansonic
Just in case anyone is confused by this: (maybe it's just me?)

    
    
        // Alan's notes:
        // I'd like to put a mu in here for micro.
        // Should we adopt the questionable Electrical Engineer policy of using
        // "u" to indicate micro?  I've added "uF" for microfarad later on to
        // tackle the most common case.
    

This is referring to using the practice of using the character "u" instead of
"µ" as the SI prefix for micro-, presumably because it's easier to type 'u' or
because a lot of stuff is still stored in ASCII. Notably, this appears to be
the only SI prefix that uses a non-Latin character, thus the inherent problems
when used in documents/systems that only support the Latin alphabet or
otherwise make it difficult to use non-Latin characters.

Disclosure: Graduate of EE. Didn't know we were causing so many issues all
this time with our rebellious use of microfarads :)

~~~
gaur
Speaking of questionable EE conventions, why do electrical engineers seem to
never use nanofarads? 10 nF capacitors are usually labeled as 10,000 pF or
0.01 µF, for seemingly no good reason.

Also, the ohm symbol is frequently omitted from resistance specifications. 10
kΩ is written as 10 k (or worse, 10k).

------
phasmantistes
In regards to the difference between American and European
billion/trillion/etc:

    
    
      // These number terms were described by N. Chuquet and De la Roche in the 16th
      // century as being successive powers of a million.  These definitions are 
      // still used in most European countries.  The current US definitions for these
      // numbers arose in the 17th century and don't make nearly as much sense.
    

Huh? Admittedly I'm biased, being American, but how do the American
definitions not make nearly as much sense?

By the time "billion" was defined by Chuquet and De la Roche, the concepts of
"ten thousand" and "hundred thousand" were in widespread use. Those were
followed by "million". So there's already a precedent for "we multiply things
by a hundred before coming up with a new name". How does it make sense to
change that to "but after a point, we multiply things by a thousand before
coming up with a new name"?

I could see a couple systems that would arguably make more sense:

* ten, hundred, thousand, million, billion, trillion... (no multipliers)

* ten, hundred, ten hundred, thousand, ten thousand, hundred thousand, million, ten million, hundred million, thousand million, billion..., million billion, trillion... (use all previous multipliers before creating the next new name)

Admittedly, the US uses neither of those systems. But sticking with the
precedent of "a hundred is the highest multiplier" makes sense.

~~~
andrewla
I think the "making sense" refers to the fact that "billion" has "bi-" as a
prefix, and "trillion" has "tri-" as a prefix. In American English, it's not
clear what is "bi-", exactly, about a billion -- two of what?

If we had skipped "billion" and gone with "trillion" = 1e9, then it would be
more natural, because then it would refer to the number of thousands; but then
the more natural nomenclature would be "bi-sands" and "tri-sands" or
something.

~~~
phasmantistes
Aha, that actually makes a lot of sense. I was only thinking about which
numbers should have unique names, not whether the names we've given them make
sense for their positions. Thanks!

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Sniffnoy
This looks like an older version of the file. I don't know where to find an
easily-linkable online copy of the current one, but it's the
"definitions.units" file included in GNU Units.

~~~
maxerickson
It overlaps with it a great deal, but it is not simply that file. Quoting:

 _This file is adapted, modified, and extended from the units database for use
with GNU units, a units conversion program by Adrian Mariano
adrian@cam.cornell.edu, who did a damn fine job collecting much of this._

~~~
Sniffnoy
Ah, I see. Yes, I'd missed the editorializing -- which I do think is worth
reading (especially about the candela), now that it's been pointed out (though
I do think he's wrong about bits and Hertz). For what it's worth, though, it
appears to be modified from an older version of the file; some of the
editorializing would be out of date if it used an up-to-date version.

------
gaur
> This means that, if you follow the rules of the SI, 1 Hz = 1/s = 1 radian/s

I fail to see how this follows from the SI definition of either the hertz or
the radian.

~~~
leni536
I always frowned upon the unit "radian". Radian is defined in terms of the
ratio of two quantities both having length dimensions. So by this definition
angle should be dimensionless. I really don't get radian.

~~~
cyphar
I've always ribbed against my physics professors using the notation of rad/s.
To be fair, they'd make it clear that the reason they used it was to remind
the students that the quantities were angular (ie \omega not velocity).

~~~
jason_s
If you work in the field of motor control, you need this. (Not only that, but
you need to distinguish electrical rad/s and mechanical rad/s; motors with N
pairs of magnetic poles undergo N electrical cycles for each mechanical
cycle.)

------
ycthrowaway2
Is this accessible in javascript?

~~~
chillingeffect
I made a small collection of unit libraries across languages. You can find it
here:
[http://www.diydsp.com/index.php?title=Physical_Unit_Conversi...](http://www.diydsp.com/index.php?title=Physical_Unit_Conversion)

