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Scuba Forum / General / June 2005Inexpensive Backup Computer?
Hi all: I'm going on my first live-aboard and was thinking I might want a redundant computer. I currently dive with an Aeris 300G and was thinking it might be a good idea to get a wrist mount one as well, just in case... Any suggestions on a relatively inexpensive, nitrox-compatible unit? Thanks. - Dave If you are going to have a backup computer, make sure you start using it right away, or else it will give you a false profile. On my recent trip to Cocoview, one of our party of 4 locked himself out on his Cobra, he just borrowed another computer for 48 hours, blithely ignoring the fact that his diving was unsafe. A few days later, he did the same thing again. Hangovers and headaches were no deterrent, neither was his age of 58 years. A real macho man. He said himself that he was not planning on getting bent. Very reassuring. Last time I travel with him. A redundant computer is a good idea. Make sure you drink lots of water. Hope you have fun. Where are you going? > Hi all: > [quoted text clipped - 5 lines] > > - Dave > If you are going to have a backup computer, make sure you start using it > right away, or else it will give you a false profile. If what you mean is that I should dive with the backup from the beginning, that's the plan. It'll go on all the dives with me and my primary computer. The trip is to the Cayman Islands on the Aggressor - my first live-aboard (and in fact, my first night sleeping on a boat!) Thanks for the help. > If you are going to have a backup computer, make sure you start using it right > away, or else it will give you a false profile. [quoted text clipped - 9 lines] > > Make sure you drink lots of water. Hope you have fun. Where are you going? You're right but that's a different issue. His computer did not break down, he ignored it. No amount of redundancy will solve the stupidity problem. Adam > Hi all: > [quoted text clipped - 5 lines] > > - Dave I have the Aeris Atmos 3 and like it alot. You can get it from http://www.scubatoys.com for about $ 250.00, and since they're a "real" shop, it comes with a full manufacturer's warranty. I haven't used your model, 300G, but the fact they'll be both Aeris' should make menu navigation easier. Chris Hi, Call me silly but I always carry a backup computer with me. It's called my dive watch, my gauges and a set of plastic dive tables. I did the Belize Aggressor last fall and forgot to reset my Nitrox on my computer so it errored out on me underwater but I was able to go to the dive tables, watch and gauges (and after 15 minutes or so of calculations) continue diving the rest of the day. :O) Oh, they're cheap! r P.S. I'm a computer guy and I've learned never put all your faith in them. > Hi all: > [quoted text clipped - 5 lines] > > - Dave > Call me silly but I always carry a backup computer with me. It's called > my dive watch, my gauges and a set of [quoted text clipped - 3 lines] > gauges (and after 15 minutes or so of > calculations) continue diving the rest of the day. :O) Oh, they're cheap! So you took your maximum depth for each dive and used that to figure your nitrogen loading on the tables? The obvious problem with your "cheap" solution is that you're not getting any "credit" for time spent in the shallows, so you get "cheated" out of bottom time versus someone who had the sense to carry a backup computer. If all your dives are 60' max for 35 minutes, that's not a problem. But if your dives are closer to an hour each with maximum depths in excess of 100', recalculating your profiles on tables would likely show you missed a lot of deco and that you're now dead. God knows what you meant by "reset my Nitrox" but it sounds like blatant user error to me. And then you trust yourself to be a backup "computer"? > > Call me silly but I always carry a backup computer with me. It's called > > my dive watch, my gauges and a set of [quoted text clipped - 15 lines] > God knows what you meant by "reset my Nitrox" but it sounds like blatant > user error to me. And then you trust yourself to be a backup "computer"? There are some computers that reset the oxygen percentage to a high number automatically after each dive, and you have to remember to manually re-set it before you go back in the water. Yes, this is a "user error" but it's also an easy one to make. I know I have a couple of times :-) Using tables as a back-up to a computer is a really bad idea for the reasons you point out. Renting another computer is probably the easiest and cheapest way of having a back-up. You could also get a watch/computer like a Suunto Mosquito and use that. Of course, if you're diving nitrox and you forget to re-set your main computer, you're also going to forget to re-set your back up... > There are some computers that reset the oxygen percentage to a high > number automatically after each dive, and you have to remember to > manually re-set it before you go back in the water. Yes, this is a > "user error" but it's also an easy one to make. I know I have a couple > of times :-) Actually I'd consider such an annoying "feature" to be more computer error than not and that computer would soon wind up lost on the bottom somewhere. But checking and resetting one's nitrox computer, especially if you've got one that resets high, should be as routine as checking the mix after each fill. You don't forget to do that, do you? > Using tables as a back-up to a computer is a really bad idea for the > reasons you point out. Unless he's one of those GUE types who "compute" their profile on the fly. Then a good set of tables is probably a decent backup. > Renting another computer is probably the easiest and cheapest way of > having a back-up. You could also get a watch/computer like a Suunto > Mosquito and use that. Of course, if you're diving nitrox and you > forget to re-set your main computer, you're also going to forget to > re-set your back up... Normally, Janna is my backup computer since we always tended to dive the identical profile, her not wanting to let go of my hand. Now that she's gained a whole bunch of confidence, she's all over the place and it's too hard to stay with her. For instance, she'll often follow the divemaster whom I'm going out of my way to ignore. So I've got an old Cochran that's such a pain to set on nitrox that I leave it permanently set on air and it hasn't been wet in probably three years, though I had it serviced just a year ago. It will make a fine backup on my not-soon-enough Cocos trip since I can plug the transmitter/tank unit on the other HP port and leave the display/wrist on the boat until I need it. The unit's liberal enough on air to match my Uwatec on 32% and it can log stuff that the Uwatec can't in case I ever choose to download any data (which I never do). And if Janna wants a backup she can just make sure she doesn't go deeper than me. > > There are some computers that reset the oxygen percentage to a high > > number automatically after each dive, and you have to remember to [quoted text clipped - 4 lines] > Actually I'd consider such an annoying "feature" to be more computer error > than not and that computer would soon wind up lost on the bottom somewhere. I believe it's a "safety feature" that the manufacturers' counsel advised them to integrate into their software. > But checking and resetting one's nitrox computer, especially if you've got > one that resets high, should be as routine as checking the mix after each > fill. You don't forget to do that, do you? Yes, but I might do that quite a while before I dive. My computer "resets" to EAN50 after about 5 minutes at the surface. > > Using tables as a back-up to a computer is a really bad idea for the > > reasons you point out. > > Unless he's one of those GUE types who "compute" their profile on the fly. > Then a good set of tables is probably a decent backup. The "120 rule" plus various fudge factors is a pretty clever idea (although I think Kane took it a little too far with his recreational triox class), but I've never gotten anyone at GUE to explain how to use for anything but one dive per day. > Yes, but I might do that quite a while before I dive. My computer > "resets" to EAN50 after about 5 minutes at the surface. It's been so long since I've been in the local cold & murk that I forgot there is such a thing as getting a fill from the shop and diving it later rather than getting a fill or prefilled tank to be analyzed on the spot. Your computer really sucks. What make is it, may I ask? I'd like to avoid future mistakes. I already own a Cochran. > The "120 rule" plus various fudge factors is a pretty clever idea > (although I think Kane took it a little too far with his recreational > triox class), but I've never gotten anyone at GUE to explain how to use > for anything but one dive per day. That's all one has time for by the time the entire team is ready to dive. > > Yes, but I might do that quite a while before I dive. My computer > > "resets" to EAN50 after about 5 minutes at the surface. [quoted text clipped - 5 lines] > Your computer really sucks. What make is it, may I ask? I'd like to avoid > future mistakes. I already own a Cochran. I don't believe it's being sold anymore. It's an OMS badged version of a Diverite Nitek (which is actually made by Seiko). Other than the stupid reset "feature" I really like the computer. > > The "120 rule" plus various fudge factors is a pretty clever idea > > (although I think Kane took it a little too far with his recreational > > triox class), but I've never gotten anyone at GUE to explain how to use > > for anything but one dive per day. > > That's all one has time for by the time the entire team is ready to dive. > "Alan Street" <agstreet@nonono_san.rr.com> wrote in message > > The "120 rule" plus various fudge factors is a pretty clever idea [quoted text clipped - 3 lines] > > That's all one has time for by the time the entire team is ready to dive. LOL Hi, Guess I'm lucky in the fact that I can't get an hour at 100' out of a tank. I used the Nitrox calculations for my numbers to optimize my profiles (Equivalent Air Depth, Oxygen Partial Pressure, etc. (laminated in my dive log)). Have to say, even in diving 5 dives that day I still didn't get close to max time in the water with 32-33%. As far as my computer goes, it makes you reset the Nitrox % before each dive since it doesn't assume a % between two tanks (safety reason, like you switch back to an ambient air after a Nitrox tank). I did the Nitrox reading on the tank and logged it to my log book but got distracted for a minute helping someone with their equipment and didn't reset my computer before I got in the water. Boy talk about a racket once I got a depth but it was too late to reset the % so I dove conservatively and figured out my numbers when I got back to the surface. Given that I was on my 2nd of 5 dives that day, it allowed me to have confidence that I wasn't going to over do it that day. I guess I'm a conservative diver anyway so what I lost in the tables and calculations by not doing a multi-level profile wasn't a problem and turned out I had plenty of dive time that day (my computer showed that I had only used about 40-50% of my Nitrogen levels for the day the rest of the week so it was more of a comfort factor knowing where I was than a safety thing). Randy I know a few people who do liveaboards who use Nitrox but keep their computers or tables on air profiles to be ultra-conservative in their dives. 'Course they don't do 5 dives a day at depth. >> Call me silly but I always carry a backup computer with me. It's called >> my dive watch, my gauges and a set of [quoted text clipped - 17 lines] > God knows what you meant by "reset my Nitrox" but it sounds like blatant > user error to me. And then you trust yourself to be a backup "computer"? > Guess I'm lucky in the fact that I can't get an hour at 100' out of a > tank. Lucky, or dumb. Or maybe it's dumb luck. Next time, try to not spend the entire hour at 100'. Still, even if you only spend 2 minutes at 100' and then do a nice long 2 minute ascent to 40' where you spend another 56 minutes, you do call that a 100' for 60 minutes dive on your tables, don't you? > I used the > Nitrox calculations for my numbers to optimize my profiles (Equivalent Air > Depth, Oxygen > Partial Pressure, etc. (laminated in my dive log)). Have to say, even in > diving 5 dives > that day I still didn't get close to max time in the water with 32-33%. You were tracking your residual nitrogen and surface interval time, weren't you? I suppose it's possible if your profiles were shallow enough, but a couple dives a day over 70' would probably shorten your available bottom time even on 33%. > Hi, > [quoted text clipped - 9 lines] > > P.S. I'm a computer guy and I've learned never put all your faith in them. On the other hand, if you dive and don't look at the computer before the dive, it makes me wonder what else you did not check. It's all part of the pre-dive check. Adam |
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