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Yeah, but are computers on fully-closed rebreathers truely "life-support" equipment - or can any well-trained diver do a full and safe abort with any well-built rebreather without the aid of computers? That's the question I wanted John to ask you. Rich > Computers are very convenient and I always carry tables as backup. I cut > my own using Decomm which is the best program for what I do. The computer > uses the Buhlman ZHL16 algorithm with a little conservatism added in (I > can change this on my laptop and download the changes to the dive > computer. The dive computer will keep track of ten different gas mixes and > do gas switches; I can change these on the laptop as well. The only switch > I do on deep dives is from trimix to OEA running both at a pO2 of 1.4. The > computer handles this readily. If the O2 sensors crap out then the > computer will default to a preset pO2, usually 1.3. The computer can be > used attached to the rebreather and monitor O2 sensors or as a stand alone > computer with preset pO2 or fO2 for rebreather or open circuit. Computers > can and will fail so I always carry tables. For a while I had problems > with the computer and quit using it because I didn't trust it. These > problems have been ironed out and I trust the computer implicitly. But, I > still cut tables as backup. Decomm and computer differ on same dive > because I cut Decomm so that when I enter the water I am at the bottom > instantly. I used to cut Decomm by treating a rebreather descent as an > open circuit descent for fO2 purposes. I would input a new fO2 every 30 > feet until the bottom. On the bottom it takes about 5 minutes for you to > metabolize O2 in excess of set point, so I would factor that in. I found > from experience that you get nearly the same tables if you cut decomm as > if you were at the bottom instantly at the fO2 of the setpoint. So now I > cut the tables the easy way. For a mixed gas dive with the rebreather, the > fO2 in the diluent tank at maximum depth is the same as the set point > fraction, so I never go over the set point. For most dives that I make > over and over again to the same depth and for similar times I know what > the deco is without the computer or tables. But, computers make all of the > above much simpler to deal with and makes diving more convenient. George's > point is well taken in that computers can and will fail. BTW, Decomm can > be used in a constant pO2 mode by trickery because Abdur hasn't built me > Decomm to do it automatically. > > > > On Tue, 3 Sep 1996, Richard Pyle wrote: > > > > > > anyone who ever ran windows 3.1 should be able to tell you that computers > > > crash fairly often.as a result i dont want to trust my life to a computer > > > system. - jt > > > > If a rebreather is designed right, and if the user is trained right, then > > computers on a fully-closed rebreather are a convenience, not a > > life-support system. If you don't believe me, as Farb. > > > > Rich > > > > > > > > > > > On Mon, 2 Sep 1996 gmii@in*.co* wrote: > > > > > > > > > > > In reading this account of another electronic rebreather nightmare I am > > > > amazed at the sheer stupidity and arrogance of the "tech" "engineers" who come > > > > up with this crap. Clearly anything in the breathing loop of any rebreather is > > > > by definition at the same number of atmospheres as the diver - obviously whoever > > > > designed this is one dumb fuck. > > > > > > > > For you dumb fucks out there, that means that the chips are compressed, the > > > > batteries are compressed, and the besides the obvious chance to short circuit as > > > > they are squeezed, some components, like dry cell nicads, can not tollerate > > > > compression. It is no wonder , however, that the same crowd that went for square > > > > lights fell for this bogocity. > > > > > > > > Most computer chips are hermeticly sealed, which means that they may retain > > > > compression in their voids and explode when the pressure is lowered. I do not > > > > know much about rebreathers or computers, but I think NOVRAM chips have their > > > > own batteries, so that means the chip and the battery are being compromised. > > > > > > > > Trying to encase this crap in gell would not alleveiate any of these > > > > problems, and would add the problem of water wicking down the wires and causing > > > > the endless electonic mystery. > > > > > > > > Just like most dive equipment, these devices are clearly created by people who > > > > do not actually dive for people who need a magic carpet, and the only commercial > > > > use for a piece of shit like what is described here is for instructors to teach > > > > wannabees and strokes yet one more merrit badge specialty. > > > > > > > > But, what else is new? - G > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > Send mail for the `techdiver' mailing list to `techdiver@terra.net'. > > > Send subscription/archive requests to `techdiver-request@terra.net'. > > > > > > > Richard Pyle > > deepreef@bi*.bi*.ha*.or* > > ******************************************************************* > > "WHATEVER happens to you when you willingly go underwater is > > COMPLETELY and ENTIRELY your own responsibility! If you cannot > > accept this responsibility, stay out of the water!" > > ******************************************************************* > > > > -- > > Send mail for the `techdiver' mailing list to `techdiver@terra.net'. > > Send subscription/archive requests to `techdiver-request@terra.net'. > > > > Richard Pyle deepreef@bi*.bi*.ha*.or* ******************************************************************* "WHATEVER happens to you when you willingly go underwater is COMPLETELY and ENTIRELY your own responsibility! If you cannot accept this responsibility, stay out of the water!" *******************************************************************
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