Redundant Backups

[RICoder]

First off, I find it amusing that every thread that is about computers always has people talking about computers failing...but, whatever.

I dive an AI and a non-AI on my wrist. The non-AI is a watch actually, but is a pretty robust computer. As with all things SCUBA, redundancy is good. So, to answer your question, as was already stated, buy the other stuff first, then worry about a second computer.

 

[StSomewhere]

... I think I would really like an AI... for ease of use... but have to admit.. .I would like the redundancy of a regular pressure gague (if push came to shove, would always rely on the SPG first and foremost). So, can you have both on one set of regs?

Yes, but only if your regulator's first stage has two high pressure ports.

 

[scubadobadoo]

I see lots of folks here talking about AI and failure so this seems like a good time to ask this question. With regards to signal strength, how often have any of you experienced signal loss with your AI computers? I just bought an aeris elite and am concerned. Opinions seem to vary. I understand that we are mostly talking about the possibilty of failure in this thread but what is the reality of signal loss for those of you using elite, air z, vytec types etc...

As for the original question, I agree that more than one computer for recreational divning isn't a concern at first. An SPG and a watch/bottom timer as a backup.

So, does anyone here dive with ONLY an AI computer and no backup? Does anyone trust ONLY the AI computer? Then why buy one? That's what I am wondering. Ofcourse, I just did. Cool toy I guess but at $700-$1000 it should be reliable enough to use alone! "Get rid of a hose," says the ad but then add a hose (small spg) and add another computer or backup timer because you don't feel safe enough to count on your new $800 toy. Where does it end?

But like I always say to new gear buyers, rent first so you know what you like and then buy what you want the first time and save cash in the long run by not buying cheap and then buying again later. JMHP. Good luck and thanks all for your time!

 

[Quarrior]

Here's my experience with the wrist mounted AI. I have never lost signal as long as I stayed within range of the transmitter. Pretty easy to do when it's on your back.

However, I have on occasion forgotten to synch the transmitter with the computer when I turned on the gas, mainly because I tend to turn on my gas and leave it on when I set up my gear. I check it, but I don't normally mess with it once it's on.

I have never had a problem with SPG being synched up. Now, if you have an AI console mounted system, I don't know if you have to synch them or not.

Either way, as a hi-tech engineer, I'm not ready to leave my life in the hands of the AI.

 

[verona]

I didn't used to dive with 2 computers but I do now since I experienced a failure! I had an UWATEC Smartcom which started behaving oddly (alarms going off without obvious reason) and which then just didn't work one day. Happily I had with me that day my original cheap SPG and my first computer which I had been intending to sell. So I could still dive. Scubapro "fixed" the Smartcom only for it to fail again and then they replaced it with a new one. Touch wood, the new one seems fine but I now wear a wrist computer too for redundancy reasons. But, of course, if the Smartcom failed I would still have to surface because it is AI.

 

[RICoder]

So, does anyone here dive with ONLY an AI computer and no backup? Does anyone trust ONLY the AI computer? Then why buy one? That's what I am wondering. Ofcourse, I just did. Cool toy I guess but at $700-$1000 it should be reliable enough to use alone! "Get rid of a hose," says the ad but then add a hose (small spg) and add another computer or backup timer because you don't feel safe enough to count on your new $800 toy. Where does it end?

Yup, I do. I have a SUUNTO Cobra (AI), no spg. I do wear a watch with a computer in it, but it is more a toy than a backup since, if the Cobra died, I'd have to surface anyway, as would anyone with any equipment failure.


See what I mean about it turning into a discussion of computer failure everytime someone mentions it? If someone says something about solo diving being even remotely dangerous, people LOSE THEIR MINDS! But talk about computers crapping out, and its a free-for-all...but, I digress.

The thing is, go dive with a reputable dive shop anywhere in the world and you will see divemasters diving with only computers. Hell, I don't even know anyone who dives with an SPG anymore, we all dive with Suunto AI's. Your reg is more likely to fail, your BC is more likely to spring a leak, your tank is more likely to have a bad O-ring, your hoses are more likely to kink or leak...more likely than your computer failing. This is not to say they are perfect, but they are reliable. One needs to take care of it like they do with their reg and tanks (as in service), make sure the battery is good and all that happy stuff. Still, I trust my computer more than an $80 SPG...but that's me.

</rant>

 

[Mark Vlahos]

Hi,
Does anyone have any thoughts on carrying a backup computer? I'm thinking of getting an AI unit (mares MC1 or Uwatec smart com) and having a backup wrist based computer. Now I'm not sure about the necessity of doing this, but I'm going to assume its a good idea to "cover my a$$" on this. What I'm wondering as well, is should the backup be from the same company (and use the same algorithms) or whether products from 2 different companies are a better idea... if using 2 different companies computers, then only one would be used during the dive, unless it had a catastrophic failure. I'm planning a little ahead here, as I'm not yet certified (should be in 2 weeks tho), but I want to start planning future gear purchases.

Jase

There have been numerous good posts in this thread about the uses for one or two computers and the choice to use a separate SPG with an air integrated computer... Here is my spin.

I dive with a redundant backup computer and a separate SPG. My computer is air integrated. My reasoning is simple, if I were diving with only my one air integrated computer and no SPG and I experienced a failure I would end the dive. Since I would have been checking my tank pressure regularly I should have more than enough air to reach the surface safely with plenty of breathing gas to spare. The bad part in this scenario is my dive would probably have ended too soon and I would be out of luck for any more diving that day. Since I dive with two computers if I have a failure not only can I continue the current dive using the backup, but I am good to go with more dives that day. I have the separate SPG because if the air integrated feature fails but the rest of the computer continues to work, I still have a backup for that feature.

All of the redudnancy makes me feel a little more comfortable, I check each computer against each other to ensure that depth and no-deco time calculations are not out of whack and I check the SPG against the air integrated tank pressure for the same reason. Do you NEED all of this redundancy, simply put no you do not. Is it nice to have this redundancy, yes it is. If you travel a long way for a dive vacation, or if you just jump down to the local dive site for a couple of shore dives it is nice to have the option to continue your dives even if you have an equipment failure. To this same point, it is nice to have a computer that allows you to replace the batteries in the middle of a dive trip without loosing your current nitrogen loading information, If your computer wipes this information when you replace the batteries you better make sure that you put new ones in BEFORE you start that extended dive trip.

You also asked about two different brands or algorythms. If you choose to use two different algorythms just dive the more conservative one and use the more liberal one as backup. One catch to this might be that one is more conservative under certain situations (lets say early in your dive) while the other has more conservative calculations under other circumstances (lets say later in your dive). If you are diving with two computers it is a good idea to check them both during the dive and always follow the one that is more conservative at the moment.

For recreational diving the choice boils down to your comfort level in trusting the technology, and how you want to deal with failures, balanced against the additional cost involved and the addtional task loading of checking backups.

You also indicated that you are not yet certified, but will be soon. To this I have what will probably be advice you do not want to hear. In short, DO NOT make any major gear purchases for a while. I would encourage you to wait until you have about 50 dives or so before you buy anything major. During your first 50 or so dives rent lots of different brands of equipment and different styles. If you must buy gear then look at e-bay for used gear.

Here is an all too common scenario... You are a new diver and your local dive shop talks you into a particular set of gear, or perhaps you read about somthing here or see another diver using some particular gear. So you spend the money and get that really neat gotta have it gear. You make about 50 to 100 dives and you start to realize that the gear you bought was not the best for you and what has become your diving style, so you buy more gear that is better for you and you put the old gear in a closet or you sell it on e-bay.

Yes if you rent you will spend money on rental gear instead of nelwy purchased gear and at times you will rent truly crappy gear. You will not be spending money on maintenance, you might not need to spend time on rinsing the gear after the dive if you rented it at your dive site or boat. Most importantly you can try different types of gear, Jacket BC's, Back inflate BC's, and even Back Plate with Wing style BC's. You can try different brands and models of regulators, different brands of wetsuit or drysuit, many shops rent more than one brand of computer. Use this time to try what is available so later you will purchase the right for you gear the first time you buy gear, not the second or third set of gear.

I hope this helps,

Mark Vlahos

 

[scubadobadoo]

I think my comment was more focused on hoseless computers and signal loss. I'm not sure if the Cobra AI would concern me. I have never had a problem with my computer or spg crapping out and I trust the computer part explicitly. It's the loss of air signal that scares me. Not many people have had a computer failure and most won't if they keep an eye on battery life. However, it seems like most hoseless models do crap out, even if it's only for 5 seconds. Again, I'm talking about pressure loss only related to a hoseless unit, not computer failure. I don't think I was clear enough earlier.

 

[StSomewhere]

So, does anyone here dive with ONLY an AI computer and no backup? Does anyone trust ONLY the AI computer? Then why buy one? That's what I am wondering. Ofcourse, I just did. Cool toy I guess but at $700-$1000 it should be reliable enough to use alone! "Get rid of a hose," says the ad but then add a hose (small spg) and add another computer or backup timer because you don't feel safe enough to count on your new $800 toy. Where does it end?

Add me to the list. I have a Cobra that is AI, but its not hoseless.

I looked into the hoseless AI computers like my buddies Vytec, but I had already bought an otherwise great regulator (AL Titan LX) whose one and only downside is that has only *one* HP port (DOH!!!), so I couldn't just add a backup analog SPG. So I got the Cobra instead. OTOH, I have small children and limit myself to strictly recreational diving so that I can (and will) thumb a dive for pretty much any reason. If I had a problem with the the pressure readings or something else with the computer I'm headed to the surface, I'm not going to keep diving while trying to figure it out. Obviously, YMMV.

My buddy bought a backup SPG after having some intermittent problems with the Vytek transmitter signal early on (something to do with where he was holding his hands?). Since then he has had a couple of issues with the transmitter unit that would have caused him grief if he didn't have the backup (once the transmitter battery croaked unexpectedly on a dive trip, another time the transmitter unit was smashed on a dive boat due to rough handling) and he warned me away from it if I couldn't easily add a backup SPG.

What he uses is a tiny little brass Cressi SPG on a short-ish hose that is clipped off to a D ring at the bottom of his BC on the left side. So he has a backup SPG, but its *very* small and very much out of the way, totally unobtrusive until he needs it. The entire backup cost him less than $100. Like you, he had wanted to get rid of a hose but found that it didn't work out quite like he had planned. But its still a very slick setup and he likes it better than anything else he's seen.

As to buying and buying and buying, I think if I was going on a dive trip on a liveaboard or something similar I might buy or rent a backup computer, and maybe take my old analog console (and a wrench!) as a backup, but for the occasional diving I do I think I'd be better off buying a semidry wetsuit or drysuit or ??? so I can dive more in the colder water around here than to shell out for yet another dive computer.

 

[jonnythan]

I don't think this has been mentioned.

How about you use the AI computer and non-AI computer, and keep an SPG in your gear bag. That way if either computer fails you can abort the dive but keep on diving after that.

Or... how about you save a ton of money and buy a simple SPG and simple wrist computer or two