Do I really need an expensive dive computer??

[JamesBon92007]

As you stated that you do not care to rely on electronic devices earlier in this thread, I presumed that your bottom timer is your dive watch, and not a separate tool.

No, my bottom timer is mechanical and is a separate device. I do admit to having an electronic dive watch. I don't know if they still make mechanical watches (?) So far the timer has outlasted several watch batteries and a couple of electronic watches.

I have seen that at least some dive computers are oil-filled so it seems that they would be less likely to flood with sea water so I think I would have more confidence in that design. But I don't know the actual history of such devices and which has proven to be most reliable. Sooner or later I may end up buying a dive computer but I would need to do a lot of homework first. It isn't very encouraging when I read here on SB about so many divers having a backup computer, plus many have a backup SPG in case their air integrated computer fails. So far I'm pretty sure I don't want air integrated

 

[aquacat8]

One thing I wonder is why all this focus on SPG, but not on depth gauges. I feel like if I couldn’t read my pressure, but I knew depth and time, and it was a farmilar depth, I might figure, well this tank lasts x amount of time at this depth so if no weird bubbles I’m good—but if I didn’t know depth, I mean gas consumption is so depth dependent...am I missing something here?

Oh yeah the computer has the depth gauge yawn it’s getting late

 

[woodcarver]

I use an AI computer and also have an SPG with depth guage and wear a dive watch. And carry a pony. It's not that I distrust the computer, I like backup systems. Stuff happens. I like the computer's ability to adjust based on real time, thus adding to my dive time. But they can fail. The SPG can also fail. So can my primary air supply. So I carry backups.
If the SPG or computer failed, the other allows me to finish the dive safely, rather than have to abort and surface. If the primary air fails on the other hand, dive is over, but the pony gets me home without a CESA.

 

[aquacat8]

I am thinking of shallow familiar shore dives only

 

[aquacat8]

I use an AI computer and also have an SPG with depth guage and wear a dive watch. And carry a pony. It's not that I distrust the computer, I like backup systems. Stuff happens. I like the computer's ability to adjust based on real time, thus adding to my dive time. But they can fail. The SPG can also fail. So can my primary air supply. So I carry backups.
If the SPG or computer failed, the other allows me to finish the dive safely, rather than have to abort and surface. If the primary air fails on the other hand, dive is over, but the pony gets me home without a CESA.

That really sounds good! That’s pretty much the set up I’m thinking of for solo shallow shore dives. But maybe the watch will be a watch style computer, but if I can’t afford it, just a watch.

 

[aquacat8]

@ woodcarver what size pony? Slung or backmount? Do you fill from your tank with a whip or pay for a fill?

 

[woodcarver]

I think that's why a lot of folks have a backup computer, but not a watch. The 2nd computer would be easier to switch to than the watch and depth guage.

 

[woodcarver]

I have been using the (gasp) Spare Air 3. But recently bought an H2O EAS with both a 6cu and a 13cu tanks. It will be slung, whichever tank. Filled off a full tank with an adapter. We travel for all our diving, so I needed a system that is easy to disassemble for transport. Which tank goes with me will depend on how much of her clothes I can eliminate from the suitcase; need about 3 pounds extra for the 13cu

 

[aquacat8]

I have been using the (gasp) Spare Air 3. But recently bought an H2O EAS with both a 6cu and a 13cu tanks. It will be slung, whichever tank. Filled off a full tank with an adapter. We travel for all our diving, so I needed a system that is easy to disassemble for transport. Which tank goes with me will depend on how much of her clothes I can eliminate from the suitcase; need about 3 pounds extra for the 13cu

Clothes, who needs clothes, LOL

 

[Eric Sedletzky]

If you’re going to use tables (timer and depth gauge) as a backup to a computer, then you have to calculate your dives and residual nitrogen RA/T on every dive starting with the first one along side using your computer. In reality nobody is going to do this, it takes time and it’s a PITA. The problem is that the computer can calculate your NDL much more effectively than tables, so chances are you’ll have already violated the tables by following the precision of the computer, unless maybe you’re doing totally square profiles.
The only effective backup to a computer is another computer that runs the same algorithm.
Pick one or the other, you can’t really mix the two.

There’s nothing wrong with tables, but it’s going to be a different style of diving to get the most out of them.
Divers will purposely tailor their dives to assume much more square profiles.