Trusting a computer

[Mikevet]

Confession time...I've been a diver since I was 10 years old and now 42. I dove a lot as kid but my career and kids got me out for many many years. Ok, now that that is out of the way (I feel better now)!!

My son has just turned 10 and is now certified. So, now my best friend is my dive buddy. I pulled all my DACOR equipment out of the closet and had it serviced. I go to the dive shop and say, "what are these computers you speak of?" And..." What do you mean the DM doesn't plan your dive anymore more on a dive boat/charter?

So...I get a computer. Pretty cool! Here is my question....I'm having trouble wrapping my head around relying on this computer. I still pull out the table, and I can't believe my dive times. I'm having trouble trusting the computer for no deco dives. How do you guys check your computer to know that it is correct and not accidentally going into deco because of not diving conservative enough or computer not working right? Help me feel better about these long dive times. I bought a suunto zoop.

My other question is this. I went on a dive with my computer. I sat "in the closet" and pulled out my dive table once we were told the dive plan on the boat. All I noticed was everyone else just jumping in the water. We drove over to our second stop and waited a while then people started jumping In after SIT. No one seemed to calculate anything on the SIT. it was about 50 minutes. What did I miss there? I was still neck deep in my table trying to figure out how long to wait to maximize my time.

 

[BoltSnap]

Trying to correlate dive tables to dive computer numbers isn't going to be very practical since dive computers work on "multi-level" type of calculations in real time when dive tables aren't. Your dive computer has a "plan" mode that will help you show dive time limits for your repetitive dive that are only a "guide" since they are based on square profile not multi-level.

You also need to use common sense in your diving and not dive the computer to the "limits" it shows just like dive tables. I use two computers usually with one as a backup just in case there is an issue with the main computer (it hasn't occurred yet). I haven't used a dive table for my recreational diving since I bought my first computer circa 1987/88.

 

[Bob DBF]

If you were around for the Wheel and planning multilevel dives, the computer does that constantly. If you were not introduced to multilevel diving, it gets harder to explain how the computer gives you longer dive times by constantly calculating your N2 exposure on the fly. There is no way I know of to convert the results of the computer to the tables. You can dive tables or computers, but trying to correlate the two will drive you nuts.

I use the planning function of my computer to get a max bottom time for the next dive, but once you change depth it becomes useless except as a general idea, which I like to have.

Because the computer does all the work, most divers just fly their computer. Not saying it is the best plan, just saying. Most boats that I've been on gives 50 min + SI because some computers will penalize a diver dive time for a shorter SI.


Bob

 

[Mikevet]

Hey bob, what do you mean by 50 min + SI? I know what is stands for but not sure what you are saying.

So now that everyone makes there own dive time on charter trips...how are people figuring dive times. For ex: if its a 40 foot dive and someone on the boat is diving nitrox, they could stay under greater than 2 hours probably. Is there an unwritten rule on how long people stay under as a courtesy?
The charter I went on, they told us the first dive depth literally 20 minutes before we anchored and then the second depth on the way to the second stop. So it's impossible to plan your 2 or 3 tank dive ahead of time. I did calculate everything on my computer, but I guess I'm curious if my computer is right.

 

[rongoodman]

The only thing I can think of that would make your computer "wrong" would be if you told it you were using a different gas mix than you were actually breathing. I don't understand your concern about relying on your computer when you're willing to take the tables, whichever ones you have, at face value. They're both black boxes as far as you're concerned. They take depth, previous tissue loading, and breathing gas as inputs and come up with what they think is a safe exposure time or the decompression time required to make it so. Deco for Divers is a great resource if you're really interested in what's going on.


(How can I turn Deco for Divers into a URL like we could in the old forum?)

 

[Charles2]

Like you, I learned on tables and stuck to them pretty religiously even after the computer became a universal accessory. I finally broke down a bought a computer about five years ago and now wonder why I waited so long. During the first year after buying the computer, I planned every single dive with my NAUI tables and then verified the dive with the computer. Slowly, it became apparent that the computer was not going to kill me. I still look at my tables to plan some dives, but lately, I have found that my computer's plan is more up to date and therefore more accurate than I ever was. It just takes some getting used to.

 

[Steve_C]

Your zoop is conservative as it is.
The only failure I have had with a zoop is if the battery gets low but not real low and you set your nitrox setting too early you can loose the nitrox setting which gives you an air dive.

I dive two computers. One a ZOOP, the other a Scubapro. Only difference is on dive 2 the Scubapro sometimes gives me an extra five minutes. Use to have an Aeris which was a lot more liberal.

Keep in mind that any computer is giving you conservative estimates. I do clear my computer but if I should find myself with the choice of making an open water assent and hitting the anchor with a couple minutes of "deco" and I am diving in NC there is no question which I will do given plenty of air.

 

[Freewillow]

Try to learn about different algorythms used in computors . You will discover that you can adapt the safety level that you want to have while diving. I am diving with my wife that stays ALWAYS very closed to me. Since we both have a dive computor, as long as they tell us roughtly the same thing we trust them. You claim to have a ZOOP. These are among the safe and conservative computors - some say even too conservative -.

They are, as other said, the same thing as tables but calculated at multiple levels.

To tell you the truth, on tek dive computor -, one can even change gas while diving. This is done in order to reduce deco time by using very rich oxygen mixtures, but that is another story.

 

[MB NZ]

It's an interesting question. How much do we rely on technology for our safety underwater? There are some divers who don't believe in using a computer at all, others who despite training, really have no understanding of decompression theory or tables. I think there is a balance to be struck. Perhaps, plan your dive and use the computer as a backup? If you're planning square profile dives from a table, the computer is likely to give you greater NDL due to real time multilevel calculations.

In terms of things going wrong with a computer. It's possible that the algorithm is wrong, but I'm happy to trust that is not the case with my chosen brand of computer. Alternatively, there could be a fault with the computer. I've had two computers fail in the past, one Uwatec and one Suunto. It does happen!

CurrentIy I use two identical computers, Suunto HelO2s. For simple recreational dives, I rely on these. For more challenging dives, I plan the dive and use the computers as a safety net.

 

[scubadada]

There's no reason not to trust your computer, especially for recreational dives. I would stop looking at tables, they do not reflect your multilevel dive. Your computer takes your SI into consideration for the next dive, forget about it