diving with two algorithms

[tursiops]

The OP would not be asking these questions if he had read the manuals and understood them.

He completely misses the point that the computers are using different algorithms and will give different answers, and that BOTH are "safe" for NDL usage. He also misses the point that when using two different computers, he should follow the one that is telling him to get out of the water (or ascend) first....and on repetitive dives it may not always be the same comnputer that is being more conservative.

I do not suggest diving with just one computer if he has two; if the one fails, he is likely going to have to just stay out of the water for the rest of the day. Use both computers, but follow the most conservative, whichever one it is on that dive.

All the "just use a bottom timer and tables" folks clearly have never done a series of repetitive multi-level dives on multiple days.

 

[TSandM]

Remy, this is a perfect example of the fact that decompression is not precise. We use mathematical models of nitrogen loading into the body, and there are different models that make different assumptions about how this happens. Nobody can actually measure the nitrogen absorption into human tissues, to see who is right. What we know is that, once we started using these models, we reduced the incidence of DCS to very, very low levels -- so low that it is quite difficult to test whether one model is better than another, even though they can give different answers with exactly the same input, as you discovered by wearing two different computers through a series of dives.

As a result of these differences, there are situations where one computer will indicate a deco obligation while another does not. This doesn't mean one is right and one is wrong; it means that that dive or series of dives has entered an area where there is some increased DCS risk. Some people deal with this ambiguity by buying a "liberal" computer that allows them more bottom time without scolding them. Others deliberately buy something like a Suunto, which tends to be more conservative. Some people, probably wisely, just keep their dives conservative enough not to annoy any computer. Some people get the education and training to manage decompression obligations, on the occasion that they decide to incur them.

Understanding what is going on when a computer is calculating your "no deco" time is a good idea. There is an excellent book available, Mark Powell's Deco for Divers, that can help you understand why your two computers give you different answers, and help you make better decisions about how to shape your dives for your desired level of safety.

I do agree that using two computers as you are doing, and just following the one that's giving you answers you like, is not a wise choice for safe dive management.
W

 

[RJP]

I'd also point out to the OP that there is no reason whatsoever for this thread to be in "Advanced Scuba Discussions"

 

[kafkaland]

Remy,

you may want to read this sad tale of a diver who had difficulties with dive planning and management. He did many challenging dives, and survived, until he didn't:

Accomplished Bad Divers | Precision Diving

Granted, his problem was gas management, which is more lethal than improperly managing deco obligations, but there are lessons to be learned. Please, don't end up like him, dive conservatively, understand your equipment and dive plan, and get the training for the kind of diving you're doing.

 

[cocoajoe]

Remy, you seem to have a little bit of an attitude. And I say this after reading some of your other responses in past blogs. I don't know, maybe a language barrier?
In any case, people most with LOTS of experience, here on SB are trying to help you. Do yourself a favor and listen to them.

 

[waterpirate]

The OP would not be asking these questions if he had read the manuals and understood them.


All the "just use a bottom timer and tables" folks clearly have never done a series of repetitive multi-level dives on multiple days.

I would counter that given the OP level of understanding about DC's, He would be better served by reverting to tables if he has 1 fail, or violates. The above statement also makes some pretty broad sweeping assumptions about other divers log books. I am trying to help a new punter here stay out of trouble till he knows what he does not know yet.
YMMV
Eric

 

[Remy B.]

I do agree that using two computers as you are doing, and just following the one that's giving you answers you like, is not a wise choice for safe dive management.
W

I follow the more convertatism one, and add more time at 5m, since as you mention it can't be granted as precise, as every individual is a bit different.

---------- Post added February 8th, 2015 at 02:27 PM ----------

Remy, you seem to have a little bit of an attitude. And I say this after reading some of your other responses in past blogs. I don't know, maybe a language barrier?
In any case, people most with LOTS of experience, here on SB are trying to help you. Do yourself a favor and listen to them.

If it sounded like that, my apologies, I'm actually asking to the more experienced to understand the differences, the big part of misunderstandings in a internet forum, is you can't see the person nor you did dive in this case with him, if we all where in a reunion it will be a lot different more information can flow and better examples shown.

Did I blown the NDL limit on the Punk Pro, yes I did, but did not kepth my self there to keep racking up Devo time, I ascended with plenty of air and continue diving for 30 minutes more, my deco time did not change, I followed the deco time, plus safety plus my own additional time and still end up with enough air, if one of you had been there with your DC, you will probably say my DC is either bad, or over-conservationist, that I don't see any problem in it.

I'm not saying that it is good to blown your NDL, under the circumstances I deside to do so this time, and as I followed the more conservative DC, plus my own added time, which DC is right probably both are, since they run different calculations, but honestly I was not expecting that much of a difference, but I can see I was expecting wrong.

---------- Post added February 8th, 2015 at 02:38 PM ----------

I would counter that given the OP level of understanding about DC's, He would be better served by reverting to tables if he has 1 fail, or violates. The above statement also makes some pretty broad sweeping assumptions about other divers log books. I am trying to help a new punter here stay out of trouble till he knows what he does not know yet.
YMMV
Eric

I definately will make a mistake trying to correct in a multi level dive following tables and will end up at the surface after 30min thinking I may had got bend, if I was doing square profiles and with a watch I can, but I don't, I better of with the magic box, at least with the little experience I have and little training, and it gave me more accurate NDL that the ones I can produce in the way I dive.

 

[StefinSB]

I would counter that given the OP level of understanding about DC's, He would be better served by reverting to tables if he has 1 fail, or violates. The above statement also makes some pretty broad sweeping assumptions about other divers log books. I am trying to help a new punter here stay out of trouble till he knows what he does not know yet.
YMMV
Eric

I am not sure why tables would enlighten the OP on deco theory. One can follow a table without ever understanding the underlying basis. This argument is like saying that an engineer is only good if he knows how to use a slide ruler.

 

[waterpirate]

This is not an argument, it is an attempt to help educate a new punter who does not get it. If he had bought two slide rulers that were identical, we would not be having this discussion.

To the OP, pick the DC you like, sell the other one, and buy an identical one to the one you like. See? Problem solved without emotion or conflict. No knowledge gained, no questions to ask, just follow your DC's you will be fine.

Why would knowledge of tables enlighten the OP or other readers about deco theory? Surely you jest Shirley?

Eric

 

[Tony387]

To the OP...this is a really bad way to begin your diving career. The fact that you continue to argue with knowledgeable divers giving you very simple, straightforward advice just further proves you're not getting it. Have fun and dive safely. It's just not that difficult.