The BACNET-L e-mail list has been busy this week, and unfortunately it's one of those periodic topics: we need more "Engineering Units" for some reason or another, and once that get started people start coming up with all sorts of additional units, whether there's a use case for them or not in the world of building automation.
So, if we're gong to add more willy-nilly, I propose a unit to measure the BACnet committee's consumption of beer in the evenings during meetings: firkins per folk per fortnight (in the FFF measurement system: http://en.wikipedi.org/wiki/FFF_System), or fff.
A firkin is 72 pints (http://en.wikipedi.org/wiki/Firkin) and a fortnight 14 days, so 1.00 fff = 5.14 pints per person per period(24h). Clearly a number that should remain in the fractional range.
Tempting to say that that would call for a FLOATING_LIMIT alarm algorithm but one could make a case for OUT_OF_RANGE or even CHANGE_OF_STATE(FLOOR), though the last is usually used for tequila.
Once we get the units, we'll work out the rest.
Hi Bill,
ReplyDeleteFunny, I was thinking the same thing (that we'll soon hit the 255 limit). Too bad ASHRAE didn't reserve the first 32,767 possibilities instead.
The trouble is, creating custom units (vendor proprietary) is useless in an inter-operable world. Also, it could be argued that the units being requested is a way of seeing which application domains BACnet is being used in.
Although this is decidedly non-committee like, I think the idea of custom units should be scrapped, and instead, an online units-registration process (on BACnet.org) should be put in place. So, if we (Delta) want a new unit, we just take out the next available number. When the Standard is next published, it includes all the new entries that have been made by the various companies. Of course, they'd have to be some watch-dogging to ensure your "FFF" unit didn't make it in. :) I'm thinking something similar to the vendor ID process.
Anyway, that's my 2 cents, because I don't see the problem going away.
Greg Holloway
Delta Controls