Re: gEDA-user: [OFF] high current amplifier

[John Doty <jpd@xxxxxxxxx>]

On May 20, 2009, at 1:31 PM, der Mouse wrote:

>>>>> ~5 tons, enough for a 3000 sq ft house.
>>>> And neither makes dimensional sense ;-)
>>> 1 ton refers to the equivalent cooling power as melting 1 ton of  
>>> ice -
>> Still not dimensionally right.  Need time in the denominator.
>
> Yes - "per hour".  A ton of cooling is 12 Kbtu, about the heat of
> crystallization of one ton of water, per hour.
>
>> Why do engineers use so many whacky units?  Why pretend Rumford and
>> Joule never existed?  What's wrong with watts?
>
> The same reason people will say "a bulb shedding about 40 watts of
> light" when they really mean "about the light given off by a
> bog-standard 40-watt light bulb" (meaning maybe as much as 6 watts of
> light).  The same reason people still occasionally cite weight in
> stones.  The reason people say thing like "weighs about two kilos"  
> even
> though "two kilos" is a mass, not weight, measurement.  The same  
> reason
> machine screws are still sized with small integers (as in the 6 in
> "6-32") rather than overt measurements.
>
> That is to say, tradition and convenience.

Good excuses for the masses. Not so good for engineering, which  
depends on precise communication. Crashing a spacecraft into Mars is  
pretty inconvenient, and we'd prefer not to make a tradition of it.

>
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John Doty              Noqsi Aerospace, Ltd.
http://www.noqsi.com/
jpd@xxxxxxxxx




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