Air Integrated Computers "Could Potentially Kill You."

[Angelo Farina]

No, you should follow what that computer tells you. It is good enough for those purposes. He is saying that in terms of the algorithm being used by a computer, you can do better.

Sorry, but I do not follow you on this. What does it mean "better"? Less conservative is better? Closer to the US Navy tables? Or do you mean those advanced algorithms available on some AI computers which take into account the "effort", evaluating it based on air consumption? In this latter case, I can see the point of preferring an AI-equipped computer over a traditional SPG...
Something, indeed, that I always did take into account also using the tables. Whenever air consumption had been larger than my usual SAC rate of 13 liters / minute, I always employed the table of the same maximum depth, but of a longer time, corresponding to the same air consumption I had in a normal-effort dive of this longer duration.
Example: my classical dive of 30 minutes at 30 meters, requiring a short deco stop of 3 minutes at 3 meters. The pressure at bottom is 4 ATA, hence my SAC rate is 13x4= 52 liters/minute. In 30 minutes, I typically use 30x52 = 1500 liters, which is roughly half of my 15-liters tank at 200 bar. Hence typically I still have 100 bars when I reach 9 meters and launch the SMB. Suppose that I see that the SPG indicates 67 bars instead of 100, it means that I had an anomalous air consumption, and instead of using 1500 liters (half of my tank) I had used 2000 liters (2/3 of my tank). I consider the extra air consumption equivalent to extra bottom time, and I follow the table for 30 meters, 40 minutes.
Of course my super-cheap Leonardo has no knowledge of the air in my tank, so he cannot make this adjustment to my deco stop. Does an AI-equipped computer makes the correction as I always did with the tables, or the pressure transmitter is simply used for sending an acoustic warning when the pressure falls below a threshold?
If this is the case, I really do not see the point of an AI computer.
If instead the knowledge of the pressure in the tank allows the computer to factor this in the deco algorithm, then probably the AI feature starts to become quite useful and important... And I understand why you say that a better computer can be safer than my Leonardo.

 

[saxman242]

I consider the extra air consumption equivalent to extra bottom time

Why do you do this?

Is there any deco data that suggests exposure to a larger volume of air at the same partial pressure is in any way equivalent to exposure to a smaller volume of air, at the same partial pressure, for a longer period of time? I don't recall seeing volume anywhere in any of the calculations.

 

[Boston Breakwater]

Why is the transmitter so exposed?

I've had things fall on me and my transmitter was the least of my worries.

That's not even in the original post.

I thought? I read somewhere......
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Whilst a minor amount of off-topic posting may be overlooked, the general rule is your posts or threads must be relevant to the forum or thread in which you are posting.

It was also irritating hyperbole.

A few days ago a Staff member actually told someone " To just leave...You'll be forgotten soon enough..
Awesome....

O.K. I'm good.

 

[tursiops]

What I did not understand is why @tursiops wrote that it is not recommended to use this computer for deco.

See the Cressi Leonardo manual, page 50, for example.

 

[Angelo Farina]

Why do you do this?

Is there any deco data that suggests exposure to a larger volume of air at the same partial pressure is in any way equivalent to exposure to a smaller volume of air, at the same partial pressure, for a longer period of time? I don't recall seeing volume anywhere in any of the calculations.

This is how I was trained using the US Navy tables (in 1975). These tables are declared to be "reasonably safe" when diving with modest effort, and the recommendation was to use a table of longer time when the effort was heavier than "modest". Always done this, never got bent... A few minutes of extra deco, or starting with a deeper stop, cannot hurt, it can just be a bit boring...
In my knowledge, one of the big advantages of an AI-equipped computer is that it can check your SAC rate and evaluate the additional deco required if your SAC rate indicate that you made additional effort.
This is what is called the Buhlmann ZHL-8 ADT, which I understand is employed in Uwatec computers, taking into account air consumption for modelling physical exertion: Bühlmann decompression algorithm - Wikipedia

 

[saxman242]

This is how I was trained using the US Navy tables (in 1975). These tables are declared to be "reasonably safe" when diving with modest effort, and the recommendation was to use a table of longer time when the effort was heavier than "modest". Always done this, never got bent... A few minutes of extra deco, or starting with a deeper stop, cannot hurt, it can just be a bit boring...
In my knowledge, one of the big advantages of an AI-equipped computer is that it can check your SAC rate and evaluate the additional deco required if your SAC rate indicate that you made additional effort.
This is what is called the Buhlmann ZHL-8 ADT, which I understand is employed in Uwatec computers, taking into account air consumption for modelling physical exertion: Bühlmann decompression algorithm - Wikipedia

Gotcha. It's using consumption rate as an extrapolation of physical effort and adjusting conservatism based on that, rather than claiming that there is actually a difference in nitrogen absorption because of the higher exchange rate. Make sense in theory. Does anyone besides Uwatec do that in the normal algorithms or is it only in Uwatec's ADT version of ZHL-8?

 

[tursiops]

This is how I was trained using the US Navy tables (in 1975).

I guess there has been nothing learned since 1975, and no better tools developed, and no more experience. Too bad.

 

[Angelo Farina]

See the Cressi Leonardo manual, page 50, for example.
View attachment 586627

Ok, I see that. But still I do not understand.
When I reach 9 meters, I watch my SPG (for assessing the air consumption, as already explained), I take note of the maximum depth and of the total elapsed time, and I look at the US Navy tables for knowing my deco stops. Before I had this cheap computer, that was all, as I had nothing suggesting me a different deco plan.
Now I have this computer, which of course was not designed for being the primary deco planner. In fact for me it is basically a redundant timer and max depth meter. Being not AI, is not a redundant SPG, but OK, my SPG never failed me in 45 years, so perhaps it does not require a lot of redundancy...
But this cheap computer also suggests me a deco plan, which can be longer than the plan suggested by the US Navy tables. What can be the risk following such a longer deco plan, instead of the less-conservative plan provided by the US Navy tables? Making some more minutes of deco stops cannot hurt. Where is the danger?
My only explanation of the warning in the manual is related to air consumption, which means that for being safe for deco a computer MUST be AI-equipped, and running an algorithm which takes air consumption into account for increasing the duration of deco stops when there was anomalous physical exertion.
Possibly this Leonardo asks me to make more deco stops than the tables because its algorithm is already tuned for extreme physical exertion, whilst the US Navy tables were designed for modest exertion...

 

[Ana]

Anything and everything could "Potentially Kill You" but dive computers seem to be so far down the list I wonder why even bother to have a thread about them

Just finished a solo dive and as most of the times I used my dive computer. Did few minutes over an hour on 47 to 55 feet of hard bottom...I've done this dive hundreds of times throughout the decades but I'm aware people get hurt doing this same dive I just did.
What are the reasons for divers getting hurt? That should be the question, I sure don't know the answer, but I think is ridiculous to blame one piece of equipment.

As far as comparing air integrated to manual transmission cars, please keep in mind no modern car has true "manual transmission" at least not in Germany, UK or Spain do t know other countries but you stop on a red light and they go on some sort of engine hibernation until you give them fuel ..... Pleeeease..... they have so much computer controls I couldn't even make them stall.

 

[saxman242]

whilst the US Navy tables were designed for modest exertion...

Could be that the Navy tables were designed for navy use, and as such, have different risk tolerances. Could be things have been learned over the past 50 years.