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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'. >
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