Dive Computer or Tables - which is safer for a newer diver?

[Lopez116]

Many may disagree here, but I think a computer is safer for a new diver. Why? New divers may (often do) have issues with buoyancy control, task loading/not paying attention to depth, and so on. It's easy to be deeper than you planned on a nice wall dive in Cozumel, for example...how many of you have done it?

Then you add in a camera and all bets are off

I normally keep my SPG in my left hand and look at it constantly throughout the dive. So, as of yet, losing track of my depth hasn't really happened. If anything, I am overly-conscious of my depth.

Regarding buoyancy, however, there have been a few times where I have been underweighted and at the end of my dive, it has become harder to control my buoyancy in the last 10 feet or so. I don't think I was ascending from those last 10 feet too quickly, but I was not in as much control as I would have liked to have been. It got me thinking about what the proper ascent rate is and how it might be easier to ensure I stay at that safe rate with a computer - rather than my current practice - go as slow as I possibly can.

Any input with regard to ascent rates and computers specifically? Or, any tips for proper ascent rates and specifically the last 10 or so feet???

Thanks for everyone's input so far. This forum is great.

 

[electrix]

My dive computers can be plugged into my laptop and downloaded, I can enter my tank size, dive location, conditions etc it gives me my sac rate a graph of the dive with depth and time lots of information.

 

[mathauck0814]

Any input with regard to ascent rates and computers specifically? Or, any tips for proper ascent rates and specifically the last 10 or so feet???

1 ATA/min is a good guideline, though on recreational profiles I try to do more like 10ft/min. For fun, some friends and I frequently do 10ft/min up to 10 feet and then strive for 1ft/min from there. It's hard, but it can be done. I tend to feel best when I take my time coming up. Nothing wrong with hanging out under the boat for a while. Besides, you have the greatest % pressure change in the last stint before the surface. That's not where you want to be rushing things.

 

[eelnoraa]

I think computer is safer and more convinient. It also allows longer dive time because it credits diver for multilevel profile. However, I suggest don't take the NDL time from the computer blindly. Do understand the concept behind it, and even cross reference with table value.

Take the auto I'm stupid vs manual I'm stupid analogy. When the auto works (and it may work forever), you push the gas, car goes, and simple and no complication. However, if one day it acts up, you want to be able to know it by monitoring the RPM or engine sounds, etc. You don't want to start your road trip to grand canyon and have your car break down in the middle of no where.

 

[Lopez116]

My dive computers can be plugged into my laptop and downloaded, I can enter my tank size, dive location, conditions etc it gives me my sac rate a graph of the dive with depth and time lots of information.

Ok, that's actually pretty cool

 

[Them]

I suspect the safety is about equal for new divers. DCS as a whole makes up a small part of the diving risk equation and new divers mitigate that risk successfully using either tool (and shallow dives/high SAC rates also help).

The caveat is that using tables means remembering to mark start of dive time. That is something even experienced divers can and do forget (judging by the number of diver photos I've seen where the bezel marker was at 12), and noobs will too. If you don't know how long you have been under you aren't really diving by tables.

I see the dive computer as like a spell checker. If you do everything right it makes no difference. If you make a mistake it gives you a chance to correct it before things get embarrassing.

As a side note, has anyone else noticed that their spelling has improved due to computer spell checking? My spelling used to be like William Clark's (ever read the Lewis & Clark journals?), but today I'm more likely to make a typi than an honest spelling mistake.

 

[Lopez116]

A computer or a digital depth gauge and a timer used in conjunction with tables are tools used to create and monitor your dive plan. The conservancy and discipline of planning your dive, diving within the parameters of your plan, and accurately monitoring depth and ascent rate are driven by your decisions, discipline and ability.

Computers with dual algorithms and conservancy settings can be be used to dive very conservatively as well. Ultimately it is you as a diver who chooses to dive with discipline and to dive safely. Your training, education, practice and experience add together to give you the ability to dive safely with either a computer as your guide or with tables, timer and gauges.

To be honest, it seems like diving with dive operators in popular tropical locales is more like "the max depth here is x, dive until you run out of air or 45 minutes or so, and then come on up." This seems so counter to "plan your dive, dive your plan." Another way I started looking at it recently is to control my dive and not let my dive control me. In other words, decide upon my own max depth and bottom time before entering the water and by consulting tables, and not letting the specifics of the site and size of the tank dictate my dive. I think this is what you mean. Right?

 

[DevonDiver]

TABLES:

Pros
- Ensure a healthy degree of conservatism in your dive planning.
- No batteries to run out.
- No complicated manual to read (assuming taught on OW).
- Simplistic, easy-to-remember contingency/emergency procedures (i.e. emergency deco)

Cons
- No benefit to multi-level your dive profile
- No supplementary dive information provided
- Cannot recalculate during the dive (unless tables are carried on the dive)

COMPUTER

Pros
- Allows multi-level dive profiles to extend bottom time.
- Provides supplementary information of value to the diver: Ascent Rate, Calculated No-Fly Duration, Depth/Time/NDL/PPO2 Alarms etc
- Encourages learning and 'feel' for ascent rates etc

Cons
- Reduced integral conservatism, unless manually added by diver (adjust settings and/or adhere to boundaries from NDL limit).
- Easier to become reliant on the computer, to the deficit of proper dive planning and preparation
- Emergency deco display often complicates stress situation (if manual not studied/familiarity gained)

 

[Lopez116]

TABLES:

- Encourages learning and 'feel' for ascent rates etc

This is actually one of the biggest reasons I am interested in getting a computer. At the risk of getting a really complicated response...how do computers calculate and monitor ascent rate?

What is a good entry-level computer if my goals are to remain conservative (not really extend bottom time) and monitor my ascent rates?

 

[nolatom]

For my first few dives, my limiting factor was always air consumption, not nitrogen absorption/dissipation. So it was my SPG that told me when to begin ascent.

Later on, as I dived deeper and my air consumption improved, the nitrogen became the thing that caused me to start back up.

So the tables were fine for phase one, it made me "learn stick shift" out in the field and little harm from nitrogen so long as I ascended slowly.

Phase two, it was good to have a computer to count nitrogen ticks, since now it was more often the ticks being at "the top of the green, almost into yellow" rather than too few psi, that made me have to ascend. Computers are much more useful for Phase 2 profiles than phase 1, if you get what I mean.

And I don't know how they do it scientifically, but most computers give you some "bars" at the bottom of the display to show how fast you're ascending. Mine is zero for very slow, and five bars for too fast. Presumably this is measuring your rate of ascent using the depth (meaning water pressure) function.