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

[John Doty <jpd@xxxxxxxxx>]

On May 20, 2009, at 6:05 PM, Joerg wrote:

> John Doty wrote:
>> On May 20, 2009, at 2:36 PM, der Mouse wrote:
>>
>>>>> 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?
>>>>> [...], tradition and convenience.
>>>> Good excuses for the masses.  Not so good for engineering, which
>>>> depends on precise communication.
>>> Which measuring air conditioning capacities in tons provides.  Just
>>> because it's disorienting to those who are acquainted with only  
>>> other
>>> meanings of the word doesn't make it any less precise.
>>
>> It's poor communication. Specialized jargon. Language should
>> illuminate the issue to the widest possible audience. But here, even
>> to specialists, the language obfuscates, since using the same units
>> for heat and electrical energy would reveal the thermodynamic
>> efficiency of the technology.
>>
>
> Depends on who you are dealing with.

Of course. You have to be prepared to deal with this problem.

> When I spec'd out a catheter
> manufacturing plant the construction guys as well as the architact
> looked at me with wrinkled foreheads when I started with kilowatts.  
> "So
> what size unit goes where, then?" ... "Well, two five-ton units over
> here and we'll need another one over yonder." ... "Ah, ok, I think we
> can work that into the budget."

And *you* did exactly right. But the other guys would find energy  
efficiency issues much easier to comprehend if they used consistent  
units.

>
> Same in other professions. Taking it back four inches doesn't mean
> altitude in an aircraft ;-)
>

The first space mission I worked on did mass properties in slugs and  
feet, and magnetic properties in CGS units (pole-cm et al.). Since we  
were using magnetics to orient the spacecraft, that produced a  
collection of magic constants, both in the computer code and written  
on a crib sheet in the ops room. You can deal with it, but it's  
stupid to have to. And sometimes it produces catastrophic confusion  
(Mars Climate Orbiter).

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




_______________________________________________
geda-user mailing list
geda-user@xxxxxxxxxxxxxx
http://www.seul.org/cgi-bin/mailman/listinfo/geda-user