AI & Deco models - am I being fed a line?

[GoBlue!]

Hey all-

Was at my LDS the other day looking at computers, and I indicated that I was leaning toward the Vyper wrist-mount. The person helping me (asst mgr of the shop) said that he'd really encourage using an AI computer. I told him that I'm used to an SPG, and usually know my gas utilization without even looking for the most part.

He told me that the AI computers use the rate of gas utilization in their deco models....i.e., the amount of nitrogen the computer assumes you've loaded varies as a function of rate of gas consumption (*NOT* only depth, which is obviously the case).

Is this true? I hadn't heard anything like this before...I assumed that the air integration simply allows one to turn off their brain a bit when it comes to questions like "gosh, am I going to have enough air to finish out my dive?" which I really don't need.

Jim

 

[narcT]

I have 2 of the wrist mount Vyper's they rox! Forget that AI stuff if you don't need it.

When I bought my Vyper they didn't have the Mare M1 with RGBM. Its only $239 on leisurepro. I would look at that if I was buying a wrist computer today....

The Vyper doesn't have true RGBM (if that matters to you).

 

[jroy017]

I dive with a vytec wrist mounted. No problem everything is perfect. I'm really happy about it. As for needing AI well if you have the budget for it sure why not its a nice gadget as for differneces in bottom time you are talking about 5 min max one of my dive buddies has a vytec AI .
On the other hand if i dive with another buddy who computer isn't AI i some times get 5 min+/- depending on our respective dive profiles. In my opinion wrist mounted is better that way at least yous pressure guage and depth guage are mechanical back up vs your computer.
You have to be very unlucky so that both your pressure, depth guages (mech) and computer crap out on same dive. On the other hand if you are diving with a AI computer all it takes is one battery problem and you dont have pressure depth or bottom time....(or you bring a mechnical depth gauge on your wrist with watch or bottom timer)

I prefer the maechanical on console and computer to my wrsit.

Good luck JN

 

[Charlie99]

The Uwatec ZH L-8 ADT algorithm, pretty much undocumented, modifies the deco requirement based upon several factors including cold (how does it know what exposure protection??) and increased workload (as detected by increased gas usage at depth).

There is some validity in this, since a diver that is exercising heavily while at depth, then is at rest during deco will have ongassed more rapidly than he offgasses (i.e. non-reciprocal offgassing). This is due to an effective reduction in tissue time constants brought about by the increased circulation caused by the exercise.

I'm not a fan of undocumented algorithms, and suspect that inside recreational dive limits the differences aren't very dramatic.

I don't know of any AI computers other than Uwatec that adjust the deco algorithm based on breathing patterns or amounts.

Charlie

 

[Rice]

Do these computers ask what size tank your'e diving? I suppose that would be absolutely neccessary for determining how much air you have.

 

[Charlie99]

Rice once bubbled...
Do these computers ask what size tank your'e diving? I suppose that would be absolutely neccessary for determining how much air you have.

Tank size is not at all needed. For example, it doesn't matter if you are breathing with SAC of 0.5cfm out of a 60 cu ft tank or 1cfm out of a 120 cu ft tank --- the rate of pressure decrease per minute will be the same. The past history of pressure decrease, coupled with the history of depth, are used to predict how much longer you can stay at depth and then ascend, while still having the psi safety margin that you have selected. Nowhere is tank size needed for these calculations.

 

[GoBlue!]

Charlie99 once bubbled...
The Uwatec ZH L-8 ADT algorithm, pretty much undocumented, modifies the deco requirement based upon several factors including cold (how does it know what exposure protection??) and increased workload (as detected by increased gas usage at depth).

OK, this is exactly the info I was looking for. Thanks. The guy did point to a UWATEC as the model that he dove, so maybe he wasn't feeding me a bunch of bull. If, however, he was implying that all AI computers modify the deco requirement based on these other factors, that would clearly be incorrect based on your response.

Jim

 

[Doc Intrepid]

check your PMs.

Doc

 

[DeepScuba]

skip it.

 

[RichLockyer]

GoBlue! once bubbled...
If, however, he was implying that all AI computers modify the deco requirement based on these other factors, that would clearly be incorrect based on your response.

He was only giving you a partial load of bull.
The Uwatec is the only one that takes it into consideration, and even at that, all it can do is use it as a factor to make an already-conservative profile even more conservative.

There's not a lot of published data to indicate that a higher SAC will affect your N2 loading. Even freedivers can get bent.