Necessity of a back up computer/watch for NDL diving

[Diver-Drex]

On recreational dives I wear a computer, watch and my spg/depth gauge combo. I’ve never had a computer problem during a dive. However, my DB had a battery go before a dive, something was pushing a button in the bag. So she got my computer and I dove it as a table dive. I dove tables for years so this was no big deal.

If you need to buy a watch, depth gauge, spg or all three. Or if you aren’t accustomed to diving tables I would say get a second computer. If you currently have AI then an AI backup that uses the same transmitter is needed. Ideally two of the same computer. Or two from the same manufacturer so AI compatability isn’t an issue and the algorithms are the same.

Two computers for advanced and tech dives.

 

[WarrenZ]

I run 2 petrels the way I figure it a failure would be unlikely but if it occurs I have all of my deco status duplicated on the backup.

 

[aquacat8]

Come on... you posted this because you want cool new computer. Of course you “need” it ;-)

 

[MargaritaMike]

I grew up learning redundancy. I have spares for my spares. I have been diving with a computer since 1990. I started diving with two computers in 1997. Now, I dive with a Perdix AI as primary and a Hollis DG03 AI as a backup. I think the DG03 is more conservative. When diving I go by the Perdix. Maybe I should do it the other way. I dive with the DG03 so that in case the Perdix dies, I can keep diving. I have another Perdix as a spare AND another DG03 as a spare. Neither of the spares have ever been in the water. I'm thinking I might sell the spare Perdix and buy a Teric, which will become primary with Perdix secondary. The point is if I lose a computer while diving, I keep diving that day.

Cheers -

 

[BlueTrin]

Come on... you posted this because you want cool new computer. Of course you “need” it ;-)

I ‘need’ a Perdix AI backup

 

[Dzydvl33]

I scored a nice Citizen a while back that also has a depth gauge. Nice for if my computer dies. I also always dive with my wife and we have matching computers so, I guess that's kind of like diving with a backup computer.

 

[Diver-Drex]

The point is if I lose a computer while diving, I keep diving that day.

Cheers -

I can dive all day if I lose a computer and have a watch, depth gauge and tables. You don’t need a computer to dive, much less four!

And you realize that you can’t swap in a fresh computer during a surface interval and rely on its ascent profile? It doesn’t have any of the tissue loading from the previous dives. It works as a bottom timer only at that point.

 

[Neilwood]

Not read most of the responses but I personally change my behaviour depending on the risk/ effect basis. The risk of a failure is always a constant but the effect of that failure can vary dramatically between finishing a single dive early or having to skip multiple dives on a trip.

Single dive or single day diving relatively close to home - not bothered about wearing two. If anything happens to the computer I can simply finish the dive (using my knowledge of my gas usage and buddy or bubbles to judge my ascent). If I miss a second dive - no biggy.

Trip with multiple days/dives - I would always have a backup computer. It would suck on a long trip to miss dives. I use AI on my primary computer but on a trip I will carry a spare analogue SPG & hose in case of failure. Might have to cut that dive short but next dive I am back to normal.

 

[MargaritaMike]

I can dive all day if I lose a computer and have a watch, depth gauge and tables. You don’t need a computer to dive, much less four!

And you realize that you can’t swap in a fresh computer during a surface interval and rely on its ascent profile? It doesn’t have any of the tissue loading from the previous dives. It works as a bottom timer only at that point.

The spares become the backup for continued diving. They don't have the tissue loading, but the backup from the dive where the computer failed does. The backup now becomes the primary. I can also dive with a watch, depth gauge and tables, but if I have a backup computer, I don't have to. The spare computers save the dive trip, not the day of diving. I don't dive with four computers, but you have given me an idea. I did dive with 3 at one point when I was testing some for personal use.

Have a great day! Dive more, read less!

Cheers -

 

[MargaritaMike]

Trip with multiple days/dives - I would always have a backup computer. It would suck on a long trip to miss dives. I use AI on my primary computer but on a trip I will carry a spare analogue SPG & hose in case of failure. Might have to cut that dive short but next dive I am back to normal.

Exactly. I have to travel in order to dive, therefore, multiple computers and spares save-a-dive TRIP. I also carry spare AI transmitters, as well as a spare HP hose and SPG. I don't want to have to go home early. The SPG and hose can also save someone else's trip as can a spare computer. It's overkill, but it's MY overkill. Also, part of the reason I have all the spares is because my dive buddy (my wife) decided to quit diving and they were her computers.

Cheers -