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Scott, What if you lose a gas? You can't reprogram you computer in the water. You computer schedule becomes invalid. What then? 2 computers sounds pretty expensive, and about as useful as diving with 2 wings. You just fixed a problem (unreliable dive computer) by adding a second computer. Now the problems are compounded. How useful are your 2 computers when the deco that the computers suggests is wrong anyway? Steve ----- Original Message ----- From: <ScottBonis@ao*.co*> To: <donburke56@ya*.co*>; <techdiver@aquanaut.com> Sent: Sunday, June 11, 2000 1:00 PM Subject: Re: Oxygen Toxicity - using 100% in open water > Hi Don, again, > > While I need to emphasize that I am definitely not recommending the use of > wrist computers for extended decompression diving, the reasons you are giving > for not using them are, IMHO, not valid reasons for eliminating them from > consideration. I say again that simply carrying a second computer will > protect against any possible failure of your primary unit. > > But "what about informing two computers of my gas changes during the dive?" > you say. Well actually, it is not necessary. Consider for example, the > Cochran three gas computer. It is not a trimix computer but will handle > three nitrox / air mixes and automatically switch to the deco gasses at the > correct time. All I need to do is to program into the computer the depth at > which I plan to switch to my second deco. gas and the computer then does the > rest. In fact, I cannot change the programming of the computer after I have > entered the water. > > Consider for example, a dive to say, 100 feet on air for a long time and EAN > 50 and O2 as the deco gasses. I would need to program in 20 feet as the > depth to switch to my second deco gas (the O2). The computer would then do > the rest. > > "How does the computer know when to switch to the deco. gasses?" you ask. > Good question. Magic!!! No not really, the computer is an air integrated > unit connected to the back tanks. It keeps track of my breathing rate during > the dive. And when that breathing rate goes to zero, it knows that I am no > longer breathing off of the back tanks so it switches to the first deco. gas > (the EAN 50 in this example). Then, later in the deco schedule, when I have > progressed up to 20 feet, it knows to switch to the second deco. gas (O2 in > this case). > > As you can see, no "informing the computer" during the dive is necessary, so > a second computer stowed away conveniently, serves well as a backup should a > failure occur in the primary unit. Of course a set of waterproof deco tables > must be taken also (with the computers serving as depth gauges / bottom > timers), to serve as a second backup should something unusual occur during > the dive. After all, the well trained and experienced human brain is still > the best dive computer around, by far. > > So as I said previously, I need to emphasize that I am certainly not > recommending using wrist dive computers for extended decompression dives at > this time. But I believe the reasons you are stating for not using them are > not valid reasons to preclude their use. I do agree with you however, that > sometime in the future these computers may have reached the state of maturity > where we will be able to depend on them for extended decompression dives. > > Take care and safe diving, Scott > > > > > In a message dated 6/11/00 8:08:25 AM, donburke56@ya*.co* writes: > > << DB>A computer failure on a deco stop dive isn't nearly > that easy in that vital information about your deco > obligation went away with the computer. Perhaps one > day there will be a computer with an independent, > redundant system that can fix this properly. There > are other issues as well. > > SB> I can't speak to the "other issues", but this one > is a non-problem. Simply take a second computer. And > remember, there may be no significant difference > between the failure rate of dive computers and the > failure rate of the electronic depth gauges / bottom > timers commonly used in technical diving. > > > Scott, > The rub here is the gas changes. The Nitrex (I > think that was the name) computer needs to be told > about each gas change. IMO doing this on two > computers during a dive is a bit much. Two computers > in the same case, (but independent pressure housings) > operated by a double set of switches might fill the > bill. > > Make no mistake, I _really_ like the display on my > Oceanic but I have been screwed by electronic devices > too often to bet my life on one. > > The digital depth guages can be backed up with your > reel and bottom timers can be backed up with your > watch. It's also pretty easy to find a home for an > extra watch or an extra depth guage (like maybe on > your buddy). Since you don't need to look at these > devices until the primary fails, they can be stashed > away. Not so with a computer that must be informed of > gas changes. > > There are some watches out there that can give you > depth, so there's a possible backup to backup. > > The fact that I'm paranoid doesn't mean these devices > aren't out to get me. :) > > SB>Take care and safe diving > > Same to ya >> > -- > Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. > Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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