John Doty wrote: > 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. >
Well, I am trying. In some areas you just have to stick to the old conventions or nobody will understand. But I recently did (partially, for data storage) move to the ISO date format after a few overseas engineers "convinced" me ;-) The topper was when someone at a Scottish heliport asked me how many stones I weigh. >> 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). > Or it produces nailbiters like this one: http://www.wadenelson.com/gimli.html -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. _______________________________________________ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user