So you want to buy a new computer?

[DiveNav]

What would be more useful is to know how each one of them would treat multiple repetitive dives... some are forgiving and some are not...

HERE (nice handwritten report done by Karl at the Catalina chamber for Scuba Diving magazine) you go

Alberto (aka eDiver)

 

[ti325v]

Okay, pardon my ignorance and yes I do have a copy of deco planner.....but do you really believe every deco dive must be planned to the minute/ meter and that I cannot count on a computer that is using an algorithm that magically stops working the moment I go into deco ?
To my knowledge, and I may be wrong....ANY dive is a decompression dive....well according to SSI more then 7 meters anyway....
There is an algorithm behind deco-planner, just as there is an algorithm running in my computers. No where in the absurdly safety conscious manuals for any of my computers say anything about DO NOT USE THIS COMPUTER FOR DECOMPRESSION DIVING. In fact they are quite detailed in how to respond to decompression situations, and how to use them in decompression.
Can you please fill me in on what I am missing ?
EDIT: I just had a look at one of my manuals and the only thing mentioned regarding the computers decompression limits, is that it cannot effectively calculate decompression stops deeper then sixty meters.
I used the example of forty meters, as it is the recreational limit, and I rarely dive deeper then that anyway. So, if you are stating that it is not a "fully qualified decompression computer", I would agree....but deeper then forty meters or so I do plan the dive with deco planner. My point is, for the dive I proposed, with the computers I referenced, there is absolutely nothing wrong with diving it on these computers. Please clarify for me.

 

[Kern]

If divers want to use recreational computers for deco information that's fine. It's not what they're best at though.

Yes, you can call all dives deco dives. They can still be split into no stop, & deco stop dives & the 2 approaches can be quite different. No stop diving looks to prevent tissue saturation to the extent that it would allow a direct approach to the surface at any time. The other deals with tissue saturation after its occurred such that it precludes a direct ascent to the surface. There is some research/experience to suggest that unmodified neo Haldanian models aren't the best approach for deco stop diving.

The sort of algorithms represented have been designed, & are well tested for no stop dives. They all use "M" values as a limiting factor for the controlling compartment. Not exceeding the controlling compartments maximum overpressure value has worked well in the no stop environment. Even here however, most manufacturers are now moving to some sort of deep stop model to slow the ascent & get away from the original bend & mend philosophy. Chasing "M" values to the surface has not proven (Doppler studies) to be the best way to go about a decompression strategy. Gradient factors are used to modify Buhlmann output by altering the overpressure gradient, & bubble models don't use "M" values to prevent or control the gas phase, & so produce a different profile.

 

[ti325v]

Your points are well made, as computers continue to evolve, incorporate "unproven" to my most recent reading anyway, but strong belief in deep stops. Non Haldanian algorithms....
I agree with your post above,
Would I rely on a recreational computer for a dive to 100 meters, NO. Then again, no way I am going that deep without helium.
Would I dive to 40 meters for 20 minutes on air, deco on nitrox, and depend on the computer for deco information ?....I do it every week.

 

[The Blue Whale]

Good discussions here. Obviously a big split for those stretching beyond the recreational diver's world and even tech diving situations. I'm personally waiting for the little blood monitor that they install in your vein at the ankle that monitors the saturated gases with an external receiver. A lab was working on these for saturation divers where dives included changing gas blends at different depths. Most all of these divers did 'lock out' dives, so they could do there decompression inside the comforts of a chamber. That would be a little more than what we need in a dive computer.

 

[DiveNav]

Thanks, is´s a jungle outthere!

You are right !!!

So far we have coded 94 dive computers in our Dive Computer Research Tool :depressed:

And we aren't done yet (couple of vendors haven't responded yet ... and we know of few new models coming to the market in the next couple of months) .... I expect to easily surpass 100 once the tool is completed.

Alberto (aka eDiver)

 

[Fianoglach]

Thanks for that!! Answered a few questions!

 

[SFC_Swede]

Nice read. As a new diver, all the choices and advice from my shop have my head spinning. This is a very well thought out post.

Cheers

 

[SkimFisher]

Conservatism is the name of the game. The true validation of today's methods comes later in life. Look at some of the old timers showing up with necrosis of the long bones, and having to get joint replacements. Many of them thought they were doing it by the book in their day. Using tables adds a level of conservatism, IMO. Computers start giving you credit the minute you leave depth. I don't think there's anything wrong with using them as a backup, but I was taught that you deco off a table, and you don't get out until you clear the time on the table, regardless of what the computer says. Conversely, if my computer tells me I have more time than the table does, I have the option of hanging out. I don't think this is a bad way to do things. I'm more concerned with being able to walk when I'm 70, than I am with getting out of the water 10 minutes earlier.

So much is still not very well understood, and many "safe" practices in diving are based off of "symptomatic" vs. "asymptomatic". Well, asymptomatic doesn't necessarily mean nothing is happening. Numerous studies have shown that.

 

[Malpaso]

Computer vs no computer? The first question is do you really need a computer at all? If you are not going to engage in repetitive diving, or particularly deep diving, then provided you can follow the basic table limits, investing in a computer may be unnecessary anyhow.

You may have just saved me $300, at least for the time being.