backup computer

[Scuba fryd]

Don't those backup computers make an annoying beeping noise?

well depends on what your using i actuly never hear my buddy but some computers you can turn it off others just vibrate

 

[rhwestfall]

well depends on what your using i actuly never hear my buddy but some computers you can turn it off others just vibrate

That was a joke... you missed it...

 

[Scuba fryd]

That was a joke... you missed it...

........i see that. definitely went over my head

 

[David Carron]

So let's say you are doing a multi-level dive (for the sake of argument, on air). Your maximum depth was 91 feet, but you were there only about 8 minutes before beginning a multi-level ascent. You are at 36 feet when your computer fails after 36 minutes of dive time.

Tell me what you do next, both on that dive and the dive coming up after a 60 minute surface interval.

If I were on my own that's a generally upwards trapezoid so the average depth of 60 feet works pretty well to calculate that, breathing air, I'm a bit borderline for an ndl dive, but nowhere near starting stops at 20 feet. Depending on the exact multi-level profile I'd probably do five minutes at ten feet and call it good. If I were diving with a buddy, I'd probably just follow their ascent.

I wouldn't do another dive after just sixty minutes of surface interval with or without a computer.

 

[halocline]

If you are diving in a situation where the information on the computer is essential to your safely completing a dive, then you need two computers, and they should be running the same algorithm, GFs, etc. This basically includes overhead and decompression diving.

If you are on an expensive dive trip with several dives/day, all recreational NDL dives, you don’t need two computers to be safe, but it sure would suck if a computer failed on the first day of such a trip and you were without one for the rest. That could cost you more than the price of a back up computer.

One thing that every diver should realize is that the border between NDL and mandatory decompression is a fuzzy line, and that there are things a recreational diver can do to increase his/her safety margin when diving near that fuzzy line or when a computer fails mid-dive. Just do what the computer would tell you to do in the early stages of deco, and you can find out what that is by using the planner on the computer prior to a dive or a software planner running a similar algorithm. We’re not talking about complex technical dives here, we’re talking about how the computer behaves when a diver crosses the line from NDL. The first ceiling is almost always at 10 feet, for up to several minutes, and the 2nd ceiling would be at 20 ft for fewer minutes. So when your computer says goodnight mid dive and it’s a somewhat aggressive recreational dive (or a repetitive dive) you could slowly head to 20 feet, stay there for 2-3 minutes, then go to 10 feet, stay there for more than 5 minutes, 10 would be good (you should have the gas) and that is going to clear N2 from pretty much any dive that’s even reasonably close to either side of NDL.

But then you’re done for the day, and if there are several days left on your expensive vacation, you’re pretty limited. Maybe you can sit out for 24 hours and start fresh with a rented computer. Do they even still have the PADI wheel? I used to use that to plan multi level dives.

If I were advising a new diver, I’d say buy a single reliable computer (shearwater makes very well built and not-too-expensive recreational models) and use it, but if you’re going on an expensive trip with multiple dives/day, invest in a back up.

 

[LFMarm]

If you are diving in a situation where the information on the computer is essential to your safely completing a dive, then you need two computers, and they should be running the same algorithm, GFs, etc. This basically includes overhead and decompression diving.

If you are on an expensive dive trip with several dives/day, all recreational NDL dives, you don’t need two computers to be safe, but it sure would suck if a computer failed on the first day of such a trip and you were without one for the rest. That could cost you more than the price of a back up computer.

One thing that every diver should realize is that the border between NDL and mandatory decompression is a fuzzy line, and that there are things a recreational diver can do to increase his/her safety margin when diving near that fuzzy line or when a computer fails mid-dive. Just do what the computer would tell you to do in the early stages of deco, and you can find out what that is by using the planner on the computer prior to a dive or a software planner running a similar algorithm. We’re not talking about complex technical dives here, we’re talking about how the computer behaves when a diver crosses the line from NDL. The first ceiling is almost always at 10 feet, for up to several minutes, and the 2nd ceiling would be at 20 ft for fewer minutes. So when your computer says goodnight mid dive and it’s a somewhat aggressive recreational dive (or a repetitive dive) you could slowly head to 20 feet, stay there for 2-3 minutes, then go to 10 feet, stay there for more than 5 minutes, 10 would be good (you should have the gas) and that is going to clear N2 from pretty much any dive that’s even reasonably close to either side of NDL.

Fully agree with this in-water strategy. In addition, you should be monitoring your NDL for the whole dive so you would know what is your exit profile at the time of computer failure.

But then you’re done for the day, and if there are several days left on your expensive vacation, you’re pretty limited. Maybe you can sit out for 24 hours and start fresh with a rented computer. Do they even still have the PADI wheel? I used to use that to plan multi level dives.

If I were advising a new diver, I’d say buy a single reliable computer (shearwater makes very well built and not-too-expensive recreational models) and use it, but if you’re going on an expensive trip with multiple dives/day, invest in a back up.

Once out of the water, you can easily reconstruct your repetitive dive profile with tables or planning software and figure out what your next NDL profile should look like so that you can keep going with either a borrowed computer or a depth gauge and a bottom timer. Definitely better having a second computer from the start.

 

[DogDiver]

One of the great things about using Shearwater computers is that they will never lock up. I use a perdix AI as primary and a Perdix non AI as backup. Now if you screw up your dive. On the surface a shearwater will let you know you’re about to do something stupid but go ahead and I’ll track your next dive profile.