Oceanic Computers bad algorithm?

Rice · Dec 30, 2002

I recieved an Oceanic Versa-Pro for Christmas, I've previously used other Oceanic Computers and been happy with them.

Today i read the review of the Versa-Pro in Divernet (http://www.divernet.com/equipment/0602divertests.htm)
and I was concerned by the statement "The decompression model used by an Oceanic dive computer is based on the no-decompression multi-level repetitive dive schedules successfully tested by Dr Ray Rogers and Dr Michael Powell. These tests did not include dives deeper than 90 feet (27m) or decompression (stop) dives."

I regularly dive over 90 feet and may someday want to do some decon dives. I'm concerned about some of the other statements in the article concerning adding decompression stops long after other brands.

Am I being silly here? Should I add deep stops or other precautins on deep dives? That would be in addition to a 3-5 minute saftey stop I always do.

Thanks for any imput.
Rice

WreckWriter · Dec 30, 2002

I have no knowledge of the quality of that specific algorythm but I do know that you should NOT do planned decompression dives on that, or any other, recreational computer.

Personally, on deeper dives (still within recreational limits) I prefer a two-stage safety stop, one or two minutes at 30', another 3-5 at 20. That's what I like, its not a recommendation.

Tom

joens · Dec 30, 2002

Most of the dive computers on the market are not meant to be used on planned decompression.
Joens

MechDiver · Dec 30, 2002

I agree with WW. Recreational computers are not the means to do deco dives.

If you want to do that style of dives, you need to have the training before you do, and that will answer alot of your questions and concerns. Oceanic makes good hardware and I doubt you'll have a problem with the dives you want to do.

Also, adding "deep stops" when you don't know where to add them may not be the best thing to do. WW has a good idea on the secondary stop, or again, do the training and form your own opinion.

Phil

Rice · Dec 30, 2002

Thanks for the swift replies. I guess I was bothered by the tome of the article and the comparison with the Cressi and Suunto computers.

Would any of you care to answer the things brought up in the linked article?

MechDiver · Dec 30, 2002

Rice once bubbled...
Thanks for the swift replies. I guess I was bothered by the tome of the article and the comparison with the Cressi and Suunto computers.

Would any of you care to answer the things brought up in the linked article?

I had not read the article, but, I would be concerned with the apparent huge difference in NDL that the writer saw with the Oceanic. It would appear that the manual statement about not deeper than 90' was true and this is a shallow water computer, although I would have thought that would have made it more conservative. But, if it was me, and I was looking for a computer, I would not buy this one.

You may want to check some alternate information sites to confirm or disprove the writers comments. This is why having lots of choices in equipment makes it hard.

Phil

tech3324 · Dec 31, 2002

Rice once bubbled...
Thanks for the swift replies. I guess I was bothered by the tome of the article and the comparison with the Cressi and Suunto computers.

Would any of you care to answer the things brought up in the linked article?

This issue came up before on another board, maybe Rodales. The conclusion was that the Versa Pro being tested by Divernet was probably a bad unit and giving bad NDL data. All the Oceanic computers use the same algorithm, AFAIK from reading the manuals, and Divernet had no problems with the performance of the other Oceanics they've tested in the past.

I don't presently own a Versa Pro, but I have three other Oceanics and they are my preferred computer. I think the Versa would be a good choice.

Arduous · Jan 1, 2003

The Versa Pro has a gage mode which essentially makes it a digital bottom timer. You should use this computer in gage mode whenever your performing decompression dives. Also you should never be performing decompression dives, with out proper training. Though it may not seem so to the untrained, there is a major difference between staying with in the no-deco limits and venturing beyond.

Dr Deco · Jan 1, 2003

Dear Rice:

Deco Meters

What is of interest in the Oceanic device is that they will actually tell you its pedigree. Most deco systems only allude, at best, to any type of decompression database. You have really no idea where the database originates. In general, this is probably without consequence in practical terms since decompression tables and such are very conservative for the general population.

That is not the impression that manufacturers wish to impart, however. They do not state that they have a guideline that, if followed, is virtually guaranteed to be trouble free. Nor do they say that you are walking the knife edge. Rather they allow standing the impression held virtually all divers that the dreaded metastable limit lies only a few breaths away. If they cross the line, the bends is in their future. Nonsense.

Tables versus Meters

Divers were always taught to avoid the limit of the table, since that guaranteed the maximum nitrogen load with respect to No D limits and the safety of the following dives. One always rounded up the next deepest depth and next longest ten minutes. When using computers with repetitive dives, if you go to the limit of the meter, you are always DIVING THE LIMIT OF THE ALGORITHM if you stay the full-allotted time. This is always longer than tables (unless you always dive the limit). Do divers get DCS more often with meters than tables? No.

Why?

The DCS rate did not increase as use of deco meters became more commonplace. Why? Because divers are always using deco algorithms with considerable building safety margins.

Even if the US Navy tables (not the exceptional exposure tables, however) are dived repeatedly to their limits, humans will not acquire DCS. These tables are worthless for DCS research because they do not provide a sufficient number of cases of DCS (or even Doppler bubbles).

If you desire to get the bends with tables, what can you do? The best way would be to perform strenuous physical exercise post dive. This exacerbating maneuver has been known since 1940 to be a real beast.

Dr Deco :doctor:

Rice · Jan 1, 2003

thanks for helping. your post and techs are making me feel better. I'm a fairly conservative diver and sincerely wish to avoid problems.

It is nice that the computers manual has a comparison of the computers programming and the Navy tables.

thanks
rice

Oceanic Computers bad algorithm?

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