what does it do and what doesn't it do?

[Genesis]

sometimes you're not.

Much depends on how close to the limit you push the computer and how conservative it is. If you've got a lot of time remaining and the computer is conservative, you can probably back into the tables and be able to solve for the pressure group you are in.

However, most of the time at least, I can't do this beyond my first dive of the day. Sometimes I can't even do it for the first one. It all depends on the exact profile I was diving, what I was doing down there, how long I stayed, etc.

 

[yknot]

There have been times for me that the second dive of the day would not have been possible without a computer, as the first would have violated table times/depths. What I don't understand is the negative opinions concerning computers for rec divers. Everything we use to dive with is unnatural and subject to failure. Remember that most recreational diving does not follow a strict dive plan. I would usually run out of air before running out of bottom times but the computer does make my diving more enjoyable and allows the freedom to explore at multiple depths without the same penalties as tables.

 

[joens]

there is nothing wrong with a rec diver using a computer exclusively as long as they understand the liabilities of a computer used alone and are willing to accept it . The number of people who have used tables as backup to computers and have not discovered they go off the charts with the tables illustrates the conservatism built into the computers . if some one wants to use both they could plan dives with tables and use a computer as a bottom timer and verification that the tables were calculated properly .However I have seen divers have a computer fail and simply grab an unused computer and carry on as if they were just starting diving.
joens

 

[Aviatrr]

if some one wants to use both they could plan dives with tables and use a computer as a bottom timer and verification that the tables were calculated properly .However I have seen divers have a computer fail and simply grab an unused computer and carry on as if they were just starting diving.

If I'm diving with somebody that is using a computer, it fails, and they have nothing to fall back on(ie tables), then I'm gonna drag their butt to 15'(or deeper if I think we need actual deeper deco stops) and keep 'em there until they're almost out of gas.

Always have a backup. Even if it's just a cheap Ironman watch from Wal Mart that you start the timer when you step in, and tables to run off of that. You should have a good idea what your max depth was.

I dive computers, but I also carry tables at all times. I actually dive two computers, because most of the diving I do demands redundancy. Why two computers instead of a computer and a bottom timer? I got a Uwatec computer cheap, and I use it to download profiles to my computer. On many dives I switch it to gauge only mode because otherwise it would get bent at the end of the dive(since it is only single gas, and I may be using two or three different gases thereby accelerating deco). Whether I'm doing a 4000' cave penetration at avg depth of 90-95' or just doing a 30' reef dive....I keep redundant timers.

If you find that you exceed the NDL's based on max depth/time(even though you are within NDL's from the computer due to the multi-level nature), get some deco tables. If your computer fails, use the deco schedule based on your max depth/time.

Mike

 

[Rick Murchison]

Genesis once bubbled...
I used to "back-up log" my dives and run a table on them afterwards, for exactly this reason.

However, I found that on a great many of my profiles after the first dive the second and subsequent dives that day, while WELL within the limits on the computer, were beyond the limits on the tables.
This is clearly due to the multi-level nature of a computer dive, and the ability of the computer to track actual time at a given depth, instead of the table-based maximum-depth computation, which overstates your nitrogen loading.

I do multi-level calculations on the tables.
(but keep it quiet)
Rick

 

[Rice]

OK, I was at the turtle farm in cayman using an older oceanic single button hockey puck computer.

Mu buddy and i swam out at 10feet to avoid swell and lookaround. we gradually dropped to 20 feet. this took about 20 minutes.

then we went over the wall to 60 feet and finned along the bottom of the wall for about 35 minutes. I then checked my computer to see it giving me ZERO minutes of bottom time. I got my buddys attention and we went up to the top of the wall and everythign was fine. (true I was neglectful of the computer, a learning experience)

however. My understanding of computers was that they used my constant depth to calculate ongassing and that I should have more time at 60 feet if I spent a large amount of the total dive time shallow.

So, does it depend on the computer? Or the compartments being ongassed? or do computers just electronically interpret tables for the first part of a dive? (0 to deepest point of dive)

thanks
Rice

 

[Newhampster]

Rice once bubbled...
OK, I was at the turtle farm in cayman using an older oceanic single button hockey puck computer.

...

My understanding of computers was that they used my constant depth to calculate ongassing and that I should have more time at 60 feet if I spent a large amount of the total dive time shallow.

So, does it depend on the computer? Or the compartments being ongassed? or do computers just electronically interpret tables for the first part of a dive? (0 to deepest point of dive)

thanks
Rice

Rice,

I don't know anything about your older oceanic single button hockey puck computer but I do know that for Suunto computers, they are calculating ongassing and offgassing in 'real time' taking into account all the different depths (and times) you've been at. They do not use 'constant depth' and they would take into account the amount of time you were at a shallow (and not shallow) depth. These computers also take into account any residual Nitrogen still in your body (even from the day before). Very smart.