Dive Tables VS Dive Computer

[Kamaros]

It doesn't hurt to sit down with tables and plan a dive, including gas planning (OP may not have covered this in class) and get an idea of time/depth etc before getting wet.

+1 for gas planning.

I also wanted to note that many modern computers have some kind of planning mode that lays out the expected NDL times for different depths if you were to start diving now (or at some point in the future for fancier computers). It's like using tables, except with less chance of user error when calculating pressure groups and residual nitrogen.

 

[chillyinCanada]

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A ScubaBoard Staff Message...

thread closed for clean up. Please remember that this is a beginner's area and ratio deco 'discussions' are beyond the scope. Further, staying on topic is required.

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[chillyinCanada]

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A ScubaBoard Staff Message...

the pool is reopened. No bickering in the pool.

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[kelemvor]

Wow, I'm very pleasantly surprised by the scubaboard community! Thanks for all your answers in such a short amount of time! I think what I'm taking away is that a good understanding of tables/what a computer does is useful, but I will also be buying a dive computer
When you guys dive with a computer, do you always bring a watch and table? Or even a second watch? It seems like overkill because computers rarely fail and if they do you can just end the dive?

You got it right. For regular diving, a computer OR watch+guage+table. I wouldn't bother with both, it's just extra stuff to carry that you won't end up using. Diving already costs plenty without getting things you don't need.

 

[Neilwood]

I have to say I was taught tables for multi level dives but would never use them in real life.

Reason being that tables are great for a dive to a fixed depth or depths (for multi level) where they will give a fixed time for NDL. This is perfect if you are going to see a specific thing at a specific point for a specific time. Any deviation from the planned depth/time means the plan fails. For technical dives where there is a specific plan, tables work perfectly.

Computers allow lot more flexibility on dive time. See something shallower that you want to focus on- the computer will allow you to hang there longer and track the changed NDL. Go deeper (to follow a fish for example) and the computer will adjust the NDL on the fly to give a shorter NDL.

I generally dive with one computer(close to home on single /double dive days where a computer issue means the day gets cut short and I go home. On a trip abroad, I use my second computer as a backup which comes on each dive and shadow tracks my nitrogen loading. That way if there is a failure, the back up is accurate and I miss no dives. It is a value judgement though. I wouldn't rely on a watch/gauge to do that for me though as, due to the way the computer works, I can extend my dive through going shallower which won't be picked up by the watch and gauge. My dive time can be way in excess of the table NDL while being conservative on the computer.

 

[Centrals]

I was taught "tables" in the beginning then progressed to "wheel" for multi-level dive and eventually settled on "computer".
For "table" and "wheel" I would need to plan ahead and also have a rough idea on the max depth that I intended to dive to. No such problem when using computer but I would plan a long service interval between dive as I got older.
Since I have computer failure under water twice, I dive with two since then.

 

[chillyinCanada]

I've had 3 computer failures over the years. One was entirely my fault for messing up a battery replacement.

I now have two and definitely wear both on liveaboards though may not wear them both on extended land based trips.

A new diver needn't rush out and purchase two computers.

One computer of reasonable price with Nitrox capability could last new diver for a very long time and potentially become new diver's spare in the distant future.

 

[JohnnyC]

I will add, I still have several sets of tables, PADI RDP in metric and imperial, metric nitrox and ead, NAUI, IANTD OC and constant PO2, min deco tables, the Wheel. I want to get an eRDPML in both flavors just to have, and a set of the BSAC spiral bound tables. They all live on a shelf as a nice little piece of history that never gets used. I will cut tables for my wetnotes for technical dives. I don't even bother carrying any agency tables anymore, although during my initial MOD1 training on the Meg, we ran the IANTD constant PO2 tables for all dives. I'm still not sure why.....standards maybe?

Anyway, get a cheap computer, fully understand all of the information it's telling you, and go enjoy your dives.

 

[Eric Sedletzky]

If someone wants to learn and use tables for whatever reason, fine.
you don’t need a watch and separate depth gauge, just buy an cheap computer like a Mares Puck for $159 and use it in gauge mode. It’s cheaper and it’s also only one unit not two. Then when you get sick of diving tables and their limitations you just switch it into computer mode and let it do the work. If you upgrade to a better computer you can run the two side by side. Have the Puck in gauge mode and have your table dive/NDL written down somewhere, and have the nicer computer in compute mode. You’ll soon see how much bottom time you’re getting screwed out of using tables.

 

[JohnnyC]

Then when you get sick of diving tables and their limitations you just switch it into computer mode and let it do the work.

I just want to point this out. DO NOT switch back into computer mode and go diving before your tissues are cleared. Couple days? Sure. After you get out of your first deep dive? NO WAY JOSÉ (if it will even let you). Computers do not track tissue loading in gauge mode. If your tissues are not clear, your computer has no way of calculating for residual nitrogen in your system. To use tursiops analogy, it would be like going on a spending spree with a halfway maxed out card but you think you've got zero balance.

I know that's not at all what Eric was implying, just want to throw that caveat out there for those that aren't aware.