Exploring some back-up / redundancy options thoughts?

[Tortuga68]

Flots, I agree, if your computer... dies, head for the surface.

I do understand that, as others have mentioned, that is SOP; however it really depends on the dive. If you're at 10m or less you'll never hit NDL on a single tank, so you can continue your dive safely. I have done 21m dives on sites I know well enough to use my gas comsumption to complete the dive within NDL. If you're not comfortable with that then fine, but a dead computer doesn't have to mean the end of a recreational dive.

...having 2 different algorithms means you have 1 telling you to ascend while the other telling you you still have time. Lets say you choose to follow the less conservative one, you possibly have a backup computer that has now locked you out for violating you NDL.

That's why you always follow the more conservative one.

 

[Gren]

I do understand that, as others have mentioned, that is SOP

Long pause between when I began typing and when I actually submitted.

Of course there are circumstances when you may decide there is no need to call the dive. If you have backup (computer or timer/depth gauge) and a SPG, you could continue the dive if you have a plan. The choice is of course you and your buddy's.

I think having 2 computers giving you conflicting information is completely unnecessary. In this case, he wants an air integrated primary computer. That is the one he will be closely monitoring but the secondary may be the more conservative which he has to follow. Why not just have 2 that should agree or better yet, use the second in gauge mode?

 

[Tortuga68]

Of course there are circumstances when you may decide there is no need to call the dive. If you have backup (computer or timer/depth gauge) and a SPG, you could continue the dive if you have a plan

What I am saying is that there are circumstances under which you can safely continue the dive without anything but an SPG (or other method of measuring gas). Unless there is a need to surface at a particular time, in which case you also need a timer, for which any waterproof watch will suffice.

 

[DiverGuam]

I think having 2 computers giving you conflicting information

Different =/ conflicting. Having two different models of on-gassing and off-gassing giving NDL info is not conflicting.

---------- Post added June 22nd, 2014 at 08:33 PM ----------

What I am saying is that there are circumstances under which you can safely continue the dive without anything but an SPG (or other method of measuring gas).

There are also circumstances in which one can 'safely' continue the dive without an SPG, if one really wants to bend the idea of 'safety' to mean "whatever a diver wants to do".

After all many people dive one computer to a group. It's not safe, it just does not usually result in problems. Which seems to be how you are using the word 'safe'.

 

[HowDidIGetIntoThis?]

FredGarvin's original question mirrors my own situation. I started with a simple Atmos2 and added the Wisdom2 (AI) a couple of years later. I continued to use the Atmos2 as a semi-backup ("semi" because the AI was the only means of measuring the gas pressure) partly because there was no apparent reason not to use something I already owned and partly because I liked to be able to see my ascent rate on my wrist.

Now that the Atmos2 has died I'm inclined to replace it with the A300 CS and use the Wisdom2 as a backup. Recent posts suggest that the A300 is still bleeding edge technology and users should plan to have to turn to their backup unit. By the time the bugs are worked out of the A300 CS the Wisdom2 could be on its last legs and I'll agonize at that point whether to replace it with an spg (and maybe an simple wrist computer) or get something like the A300 XT.

An alternative would be to go for a Petrel/Atmos2 combination, which would pretty much preserve the future options.

FWIW, within the group I usually dive with, I've seen at least one of every equipment component fail but the two items that are most likely to experience problems are computers followed by camera floods as a distant second. I've loaned a computer to a buddy (topside), which makes that spare more of a needed item than the secondary reg. (so far/touch wood/thankfully). Since more than one of us carries a second (spare) computer that effectively gives us a benefit similar to an individual carrying the third unit as earlier proposed.

This has been a very beneficial thread for me and dissentient well-developed arguments are appreciated.

Thanks
HDIGIT