Air Integrated Computer - Question

[Hatul]

AI computers work out an air time based on your current consumption. But there are two implementations. Oceanic, Atomic and Uwatec allow for a safe ascent including all the stops, and Suunto and Liquivision which only work out the time remaining at depth. In the second implementation you yourself have to allow enough gas for the ascent.

With the better first implementation if diving solo you can allow the air time to go to close to zero and still make it to the surface with a reserve pressure, assuming your air consumption does not increase. If buddy diving you should allow enough gas for air sharing-- the so-called Rock Bottom.

 

[driftwood]

I used to dive a Suunto Cobra that displayed the remaining dive time. I used it as my "relaxation meter". If I was comfortable and in the zone, then my remaining dive time would skyrocket.

The Cobra was retired when it started displaying squirrelly psi readings starting around 900psi. Now using a Vyper.

 

[scubadada]

I have over 300 dives on an Oceanic VT3 and find air time remiaining (ATR) quite accurate. ATR is calculated using individual air consumption and depth. Tank pressure is measured once per second and average consumption is calculated over 90 sec. When ATR reaches zero, you have enough gas to make a safe, controlled ascent including the safety stop or any required decompression stops to surface with the tank pressure selected as end pressure when programming the computer.

See Hatul's caveats in his post, above.

 

[beaverdivers]

I should have been a little more specific; I was referring to your consumption rate and nitrogen loading. For example, your NDL is 120minutes and your burn through your air supply (80 alum cylinder in 20 minutes) vs I dive the exact same profile, but burn only 800psi (topside with 2200). Will these computers calculate the nitrogen loading based on consumption?

Atom is correct, nitrogen is not based on air consumption. However, the Scubapro/Uwatec air integrated dive computers do take into account workload.

If you have increased workload you do take on more nitrogen and your No Stop time will be less!

The Scubapro Galileo also gives you Remaining Bottonm Time ( RBT ). RBT is based on consumption rate and depth. RBT indicates how many minutes your cylinder will last till you reach your preset reserve.

We use the Scubapro Galileo Sol w/ heart rate monitor in all of our training ( OW and higher ). We have the workload set on respiration or heart rate whichever is higher. It gives us the biofeedback we need to train our divers to dive into the 21st century!

By downloading your dives, you can analyze your air consumption, heart rate, workload and nitrogen loading.

We find this information to be essencial in understanding your diving.

 

[nv]

Atom is correct, nitrogen is not based on air consumption. However, the Scubapro/Uwatec air integrated dive computers do take into account workload.

If you have increased workload you do take on more nitrogen and your No Stop time will be less!

The Scubapro Galileo also gives you Remaining Bottonm Time ( RBT ). RBT is based on consumption rate and depth. RBT indicates how many minutes your cylinder will last till you reach your preset reserve.

We use the Scubapro Galileo Sol w/ heart rate monitor in all of our training ( OW and higher ). We have the workload set on respiration or heart rate whichever is higher. It gives us the biofeedback we need to train our divers to dive into the 21st century!

By downloading your dives, you can analyze your air consumption, heart rate, workload and nitrogen loading.

We find this information to be essencial in understanding your diving.

Please define workload. I can only assume that increased workload directly relates to increased air consumption. Thank you, you and @Hatul have cleared things up a bit.

FYI - I dive a Mares Puck Air, which only gives me alarms at which I set at specific cylinder pressures. ATR, for mares puck air, is at current depth.

 

[DarkAbyss]

Slightly off topic, but I find that my Suunto Vyper Air is always showing less cylinder pressure than my analogue manometer. If the Vyper says 150 BARs left in the cylinder, the manometer says about 165. For some reason I believe that the analogue manometer is the more precise of the two, but I always stick to the lowest value.

 

[ianr33]

kload.

If you have increased workload you do take on more nitrogen and your No Stop time will be less!

While I agree with this statement, I would love to know how the computer manufacturer arrived at an algorithm that quantitates this!
Or maybe they just make a WAG with no scientific basis?

---------- Post added July 18th, 2013 at 08:17 AM ----------

Please define workload. I can only assume that increased workload directly relates to increased air consumption.

It does, but high air consumption does not imply high workload. Many new divers will have a high air consumption, due to being nervous,or constantly breathing in/out to adjust buoyancy. High workload would be something like swimming hard into a current for several minutes, so that your breathing rate and pulse is elevated. Think hard aerobic excercise.

 

[boulderjohn]

Atom is correct, nitrogen is not based on air consumption. However, the Scubapro/Uwatec air integrated dive computers do take into account workload.

If you have increased workload you do take on more nitrogen and your No Stop time will be less!

While I agree with this statement, I would love to know how the computer manufacturer arrived at an algorithm that quantitates this!
Or maybe they just make a WAG with no scientific basis?

While some people SUGGEST that increased workload MIGHT cause an increase in ongassing because of increased blood flow (perfusion) to the tissues, that HYPOTHESIS is disputed because the rate of diffusion into the tissues should still depend more on tissue constitution than perfusion. The same HYPOTHESIS would suggest that increased workload during ascent will increase the rate of offgassing. It will not depend to any degree whatsoever on breathing rate.

Note that this is all opinion that is held by some people but disputed by others. If there is a single scientific study done on this topic, I am not aware of it. If wee are talking about guesses and hypotheses, the hyothesis of this writer is that the Uwatec product described above it peddling a very debatable and expensive feature that has no real purpose.

I suggest you ask this question in the Ask Dr. Decompression forum to see what kind of response you get from decompression expert Michael Powell.

 

[nv]

While I agree with this statement, I would love to know how the computer manufacturer arrived at an algorithm that quantitates this!
Or maybe they just make a WAG with no scientific basis?

---------- Post added July 18th, 2013 at 08:17 AM ----------



It does, but high air consumption does not imply high workload. Many new divers will have a high air consumption, due to being nervous,or constantly breathing in/out to adjust buoyancy. High workload would be something like swimming hard into a current for several minutes, so that your breathing rate and pulse is elevated. Think hard aerobic excercise.

Makes a but more sense when you look at it from that angle; especially in terms of elevating HR. Is this due to the fact that you are using using more effort causing nitrogen to store in the body more? Either swimming faster etc..has more places to store?

 

[eponym]

Slightly off topic, but I find that my Suunto Vyper Air is always showing less cylinder pressure than my analogue manometer. If the Vyper says 150 BARs left in the cylinder, the manometer says about 165. For some reason I believe that the analogue manometer is the more precise of the two, but I always stick to the lowest value.

I've seen another Suunto wireless pair (computer and sender) which consistently reports about 10% less pressure than actual. Try your computer with a different sender unit to check, but I suspect the fault is in the sender. If it's still under warranty then Sunnto should replace it for you.

Hope that helps,
Bryan

---------- Post added July 18th, 2013 at 08:33 AM ----------

[If you have increased workload you take on more nitrogen and your no-stop time will be less.]

While I agree with this statement, I would love to know how the computer manufacturer arrived at an algorithm that quantifies this! Or maybe they just make a WAG with no scientific basis?

Good question. I can't say what the mfr. was thinking, but this might be what they implemented:

Once upon a time (and maybe still today), dive table users were advised to rate themselves one residual nitrogen group higher when logging a dive (H instead of G, say) if they had been working hard or had been overly cold on the dive.

Note that that doesn't necessarily imply an assumption that your nitrogen load was higher for the dive. There are other reasons to shorten dives (increased dehydration and increased tribonucleation effects, for example).

And I agree with John that the Diving Medicine forums might have something worth hearing on this topic.

-Bryan