Need backup computer advice please

[GrumpyOldGuy]

Speaking of redundancy...


Have anyone here considered "what if" the backup computer fails? Doesn't that mean you need to have some backup for the backup? With gauges (a bit more reliable and you can't "bend" them) I don't see how that is an issue. IE - even if the gauge fails, you can replace it instantly without interuption to any of your dive plans. Not so with a "backup" computer (you'd just be doing the same thing as having backup gauges in the first place).

If you calculated the mathematical odds of a double computer failure on the same trip, you would not make such a lame argument. Hint: square the odds of a single failure, a frick'in big number.

 

[Randy43068]

I need a back-up brain. The one I have needs a re-boot once in a while.

 

[djtimmy77]

Don't forget other reasons to have a backup than the computer failing on its own...

Dropping your wrist computer off the side of the boat in choppy seas, setting your tank down on your console computer, one of your computers falls out of your bag at an inoppertune time, gets stolen, etc. These are all higher probability in my eyes than the computer failing for "no reason".

 

[Mr Carcharodon]

Thanks for the reply. I asked because I do not wear a backup and wanted to understand why others do. I do not use a backup because it seems failures are rare and would consider my buddies dive computer to be a backup. If there was a failure between a series of dives I have a second computer I bring but do not wear that could be used. Of course to do that you have to know what you did on the first dive and adjust your NDL or stops. A partial sensor failure during the dive leading to shallower than actual depths does seem to be a reason to have a second computer. I have never heard of this occurring and would consider the risk low enough not to worry about it. But then apparently others think this could happen and would want a redundant computer to protect against it.

 

[vinegarbiscuit]

I've had a black cloud hanging over me when it comes to computers...no less than five failures in the past three years (three with the same model, a Cressi, despite returning it to my LDS and swapping it for a new one...I abandoned it for an Oceanic after that!) and two with a Dive Rite computer. (As a side note, two other people had computer problems during our last cave trip - fortunately, my partner and I brought two spares with us, and helped save our friends' dives.) I now always dive with two computers, whether I'm diving recreationally or not. Having a back-up that you're familiar with is a great idea...I wouldn't recommend renting a computer if you're diving on vacation (unless you like puttering with new gear and figuring out how it works).

So, yes, get a back up. Preferably a computer that has a similar algorithm. The Manta is an economical choice, and it will complement your XR-2. On the other hand, I've also used two computers with different algorithms (my Oceanic with a Suunto) without hassles. On those occasions, I always waited for the most conservative computer to clear, and planned my dives to make sure my most conservative computer wouldn't have a hissy-fit with repetitive dives. Obviously, you'll avoid those hassles if you stick with the same algorithm. A bottom timer and analog depth gauge is also a fair choice, since you can cut tables if your primary goes belly-up.

 

[Mr Carcharodon]

Don't forget other reasons to have a backup than the computer failing on its own...

Dropping your wrist computer off the side of the boat in choppy seas, setting your tank down on your console computer, one of your computers falls out of your bag at an inoppertune time, gets stolen, etc. These are all higher probability in my eyes than the computer failing for "no reason".

I did see a friend drop a computer overboard once at a site where the bottom was about a thousand feet down (we were diving an oil rig). He ended up doing the subsequent dives on a bottom timer. Having a backup in that case did help. And he had insurance which helped too.

 

[ianr33]

Serious question: how do you know which computer is malfunctioning if either of them are not just plain dead? If one of them conked out, then obviously that one doesn't work.

But if one of them were to display wrong readings, then how do you know which is the correct one? If one's depth said 100-ft and the other said 115-ft, which depth reading is correct? Or are you now have to take an analog depth gauge as a backup to the backup? Which one's keeping the correct dive time? Or are you now have to carry a bottom timer or a mechanical watch to back up the backup?

Unless you were very familiar with a site and knew what depth you were at anyway,you wouldn't know which computer was misbehaving. But............it would indicate that something was wrong. First thing to do is check your computers against your buddys 2 computers. That should make it pretty clear.

If diving solo either follow the deepest one or call the dive (judgement call)

 

[Damselfish]

Change you computer batteries before you leave on your trip and/or have the computer checked out. Now you really don't NEED a "backup"...

that's probably the least likely reason to need a backup, since most or all computers do have battery gauges. Actually, this probably makes it more likely you'll have a failure. Like the flood my husband had on the first dive of our last trip. (After the dive shop went and changed a perfectly good battery, unrequested.)

Worst case instance is that IF your all's computers fail, you dive gauges and tables for the remainder of your trip (not really a big deal actually)...

it's a huge deal if you're doing 5 a day on an expensive trip somewhere. Tables are not an adequate backup in this situation.

 

[StuartT]

I also have the aeris etite t3 as my primary computer and got the oceanic veo 1.0 as a back up. It might be too conservative for some but I typically dive 32% but leave the backup on air and try to clear any deco on the backup. That way I'm adding a lot of conservatism to my diving. It's also interesting to see the difference between air and nitrox with ndl and deco times. Having said that I think I will set the backup to 4-6% less than my actual mix(instead of air) as this past weekend the backup wanted 22 minutes of deco on our second dive but the lowest I actually had was 11 min ndl time left on the 32% I was diving. I cleared 12 min of the "deco" but my buddy had to pee and couldn't stay for 10 more minutes so we surfaced. We were at 82 min dive time anyway and I knew the computer would lock out for 24 hours but wasn't planning any more diving for a few days. Thats why I'll set the backup for around 26%while diving 32% from now on particuarly on multiple repetative dive days. My own way of adding some more safety to diving.

 

[Scared Silly]

Slightly OT, but some of this discussion reminds me of Segal's Law:

“The man with one watch knows what time it is. The man with two is never sure"