Author Topic: Wireless, air integrated, multiple gas computers  (Read 6877 times)

craigwood

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Wireless, air integrated, multiple gas computers
« on: July 26, 2008, 13:25:34 UTC »
I posted the following message in the middle of another computer discussion and did not get much of a response. I'm hoping there are forum members out there who will comment. I'm interested in experience with the specific computers and also comments on the respective decompression algorithms used, representing relative opposite ends of the conservative-liberal spectrum. Thanks for your assistance, Craig

I would be very interested in hearing about members' experiences with the Suunto Vytec DS and/or Oceanic VT3/Aeris Elite T3. I have been diving an Oceanic Pro Plus for 6 years, about 280 dives, and appreciate the liberal Pelagic Pressure Systems decompression algorithm. I have no experience with RBGM/deep stops. The Suunto algorithm does appear to be one of the more conservative. Thanks in advance for your comments.
 

NJDIVER

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Re: Wireless, air integrated, multiple gas computers
« Reply #1 on: July 29, 2008, 21:12:14 UTC »
I've been diving with a VT3 for 3 months now and have 30 dives on it.  Unfortunately I had to send it in for repair as one of the LCD read out lights went out.  That being said I would still highly recommend the unit as it is very user friendly, easy to read both in and out of water.  Though I had that problem my wife dives with one as well and has been flawless.  Need to remember it's mechanical/electrical and as with anything mechanical it can fail.  An analog back up should be considered with any computer.

Twodivers in NJ

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Re: Wireless, air integrated, multiple gas computers
« Reply #2 on: August 03, 2008, 16:36:35 UTC »
My wife and I have been multi-gas diving with Vytecs since 2005 and have had no problems. As far as the algorithm is concerned, you can set the unit to be more or less conservative. Since you didn't mention your age or fitness level, I don't know how conservative you need to be, but remember, the computer gives you time but  it's not connected to your body. It doesn't know if you're fat, anemic, old, hungover, male, female or whatever. It just takes a sophisticated wild-ass guess and tells you what you can do based on what other people have done. In the end, it may be the computer that gets the diver bent, it's the diver.

eponym

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Re: Wireless, air integrated, multiple gas computers
« Reply #3 on: August 04, 2008, 23:23:22 UTC »
I have made at least two hundred dives on a Vytec--not the deep stop model but its predecessor. I like the form factor, the display size, and the menuing system. I've used it for recreational dives on air and nitrox, and I've used it in gauge mode for decompression dives down to 150 feet.

The computer modifies its non-deco times (fairly standard, for example 51 minutes at 60 feet) per Dr. Wienke's RGBM model. The manual says that fast ascents, sawtooth profiles, and shallow-then-deep diving are all factors that trigger RGBM to reduce non-deco times. I've read Wienke's books, and from direct observation of other divers with Suuntos, I can say that fast ascents are a particular red flag for RGBM, which may result in a required (not optional) stop. You can set whether the computer takes those considerations fully into account or only 50%. One nice thing: if you blow off a required stop the computer will give you some minutes to re-enter the water and do the stop before it shuts itself down.

The user manual is available for download online at suunto's web site if you're interested in looking at it in more detail.

-Bryan
The sea is a collector, quick to return a rapacious look.
Marianne Moore, A Grave

BigTuna

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Re: Wireless, air integrated, multiple gas computers
« Reply #4 on: August 08, 2008, 21:29:13 UTC »
I'm a recreational diver. I use the "Vytec-1" with wireless pressure transmitter. I got it to back up my "Cobra-1" with its HP readout. Altho I got the Vytec as "dive vacation insurance," I realized that I could benefit by using it with the Cobra on all dives. They have identical displays, identical algorithms, and both show pressure. I find with the Vytec mounted on my wrist, I'm more on top of my numbers, and it's especially easy to track them during free ascents.

I like the Vytec and Cobra for the RGBM deco model, nitrox, good user interface, dive planning mode (lets you see how much bottom time you get for a given SI), and ability to upload dives to the Suunto Dive Manager electronic dive log (PC only). The dive log has a couple of special features: it computes your SAC rate, it displays your tissue loadings as a function of dive time as you move the cursor along the dive profile graph, and it lets you export dive data to DAN for a long-term decompression project. You can change the batteries in both, yourself, BTW.

The Vytec's pressure transmitter works very well, but you have to remember to pair it with the Vytec before you splash in. I think its documentation is a bit weak. For example, I had to figure out some things myself, such as what "FAIL" means on the Vytec display when I jump in the water. [Tip: The transmitter stops broadcasting pressure after 5 to 40 or so minutes, to save the battery. At that point the display shows "FAIL." By simply causing gas to flow (take a breath, purge, etc.), the pressure readout is restored.] For anybody who's interested, I've attached my own notes on pairing the transmitter with the Vytec.



craigwood

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Re: Wireless, air integrated, multiple gas computers
« Reply #5 on: August 10, 2008, 04:09:55 UTC »
Is anyone aware of any evidence based information regarding the rate of DCS events for conservative vs. liberal algorithm based computers?

frogfish2

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Re: Wireless, air integrated, multiple gas computers
« Reply #6 on: August 10, 2008, 14:29:57 UTC »
Craigwood,

There are really two different questions here.  Although some people might consider computers using the RGBM algorithm to be more conservative than Buhlmann-based computers,  I don't think trying to place these different algorithms on a liberal-conservative spectrum accurately describes the differences between the two models.  Unlike Buhlmann-based computers, the RGBM model takes repetitive diving over multiple days, reverse or sawtooth profiles, and ascent rates into account when it calculates stops and no-stop time.   That may mean that a RGBM computer will give you less no-stop time at depth than a Buhlmann computer on the third dive of the sixth day on a liveaboard dive trip, but I wouldn't necessarily say that makes the RGBM algorithm more "conservative" than Bulhmann. 

It's just a different model, one whose proponents (and I am one) believe more accurately represents the actual physical processes whereby nitrogen in both gaseous and dissolved phases enters and departs from human tissues.  If that is true, then RGBM-based computers might offer better protection from DCS, but I don't think there are enough data points out there to justify solid conclusions on that score yet. 

And this has nothing to do with the "conservative" vs. "liberal" settings that can be selected on most dive computers, including both RGBM and Buhlmann based computers.  (In most cases, I believe, selecting a "conservative" settings on computers using either algorithm is the equivalent of manually invoking a higher altitude setting.)

That said, I don't know the answer to your question.  I'm not aware of any studies looking at the rate of DCS incidents for different kinds or makes of computers, or for Buhlmann vs. RGBM algorithm computers, or among computers using different conservative-vs-liberal settings.  Since RGBM implementations on dive computers are relatively new, I suspect meaningful comparisons of  Buhlmann vs. RGBM computers in terms of real life DCS incident rates would be very difficult to do. 

Frogfish2
« Last Edit: August 10, 2008, 14:36:20 UTC by frogfish2 »

craigwood

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Re: Wireless, air integrated, multiple gas computers
« Reply #7 on: August 10, 2008, 17:23:02 UTC »
DAN's Project Dive Exploration should eventually shed more light on the influence of depth/time profiles on the development of DCS. Since started in 1999, DAN has collected in excess of 150,000 dive profiles with nearly 50 episodes of DCS. The goal is to collect more than a million dive profiles. Though not a primary outcome, information concerning the development of DCS associated with the use of various computers and/or algorithms may eventually be available from this study.

It is tempting to think that a more conservative algorithm should be associated with a lower rate of DCS than one that is more liberal, however, the data to support this belief are lacking. It may be that all algorithms currently in use result in very low rates of DCS that are mainly dictated by personal and environmental variables and critical performance characteristics such as ascent rate. I participate in DAN's PDE in order to make a contribution to a better understanding of DCS. I would encourage others to consider participation as well.

 

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