Basic computer questions

[gcbryan]

As everyone has mentioned more or less, the key to using a computer is to think. Look at the bottom time and depth more than at the NDL number. That will cause you to think back to what you know from the tables and you can decide if what you are doing is reasonable. If you just look at the NDL time remaining you are relying on your computer too much.

Try to get to the point where you can guess how long you have been down, then look at your computer to see if you came close. This keeps your brain in the loop.

 

[progressweasel]

I have been diving for a long time and I have plenty of dives just using tables but I much prefer computer diving as I feel it adds enjoyment to an already fun thing. That said, you cannot turn off your brain. I like to look at the profile of my dives to make sure I am doing what I think I am doing during a dive. You still need to avoid sawtooth profiles, ascending too quickly, ... but with a computer I believe you can focus on the enjoyment of your surroundings more with a greater degree of confidence in your profile.

I can highly recommend air integration as it allows for one stop shopping for info. Yes, I know that people will saw that provides a single point of failure as well but you can abort the dive for this or have a SPG as a backup (as I do) and revert to tables should a failure (remote chance) occur.

Options are great.

 

[gcbryan]

Air integrated is a personal choice of course. I don't care for it not just because if it goes you still need a SPG but because a lot of it is clutter. I don't need a computer telling me how long it thinks my air will last if I stay at my current depth because I will not be staying at my current depth. Also it adds just one or two more numbers to an already clutter display. Many people like this option however.

 

[BigTuna]

Here's an example illustrating why an air-integrated computer can be useful.

Suppose you've just done a lot of 33-foot shore dives. Your surface air consumption rate is 1 cuft/min, and you use an Al80 tank, for which the air characteristics are 77 cuft at 3000 psi.

At the surface (one atmosphere), your tank will support your 1 cuft/min consumption for 77 minutes. That's 39 psi/min. So at 33 feet (2 atmospheres) on your dives, you'd consume 78 cuft/min. So when you see an "extra" 780 psi on your SPG, you instantly recognize you have an extra 10 minutes at your depth. Being human, you get used to associating 10 minutes with an "extra" 780 psi. [In this example, "extra" gas means gas beyond what your pre-dive planning has told you is needed for your ascent profile.]

Now let's suppose you're on your first 100-foot wreck dive after all those shallow dives. You note an "extra" 780 psi on your SPG. Quick--how much extra time is this? If you haven't planned your dive well and don't pause to think, your recent experience might give you a knee-jerk answer of 10 minutes.

Unfortunately, since you're now at 4 atmospheres, you only have 5 extra minutes, and the missing 5 minutes could get you in a world of hurt.

An integrated air computer can safeguard against making this simple mistake, since it estimates time remaining based on your current depth. Hopefully the clash between its report and your knee-jerk reaction will jog you to start thinking. Hopefully also, you also won't start relying on the computer's time numbers to the exclusion of all thinking (this possibility is why some people disklike computers).