Air Time Remaining At 0 Bar

[Boga]

I'm thinking about buying a new computer.

When Aladin Air X appeared (years ago, and it was the first air integrated
computear available in my country, Spain), I rushed to buy it.

But I was surprised when I saw that the Air Time Remaining (ATR) indicated
0 minutes when you still had 50 BAR in your tank. And you could change this
value via software.....but your limit was 30 Bar. It was impossible to
adjust the computer for 0 ATR when the pressure was 0 BAR.

I know this is safer, but I'm an experienced diver, and I want to know
which are the real numbers; I don't want that the machine lies me.
It's like if the computer would tell me that I'm down at 40 meters when
I'm only at a depth of 35 meters. It's safer, but it's not the truth.

That's why I decided not to buy an Air Integrated Computer.

Since then, I've been searching for an AI Computer that tells me the real
ATR, and tells me 0 ATR when it reaches 0 BAR. I've found nothing.

Since then I've been diving with my old Suunto Solution. I'm happy with
him, but now I need a Nitrox Computer.

I was thinking about a Suunto Vyper, but it's too conservative, and I know
that the Vytec (the Suunto's AI and three mixtures version) is also a liar
(no 0ART at 0BAR).

My other thinkings are about the Oceanic VEO 250 (which I think is just a modern Versa pro), that I think it's a bit less conservative than Suunto.

I tried to find if the AI version (the VTPro) was a liar or not. I
downloaded the manual, but I've not been able to find if the ATR says 0
minutes when it reaches 0BAR (I know this shouldn't be a factory set, but
I couldn't find anything about it).

Anyone has any information about the ATR limits in the VTPro, and if it's
possible to set them at 0 BAR?.

Anyone knows any Air Integrated Computer that says yor ATR is 0 when it reaches 0 BAR?, that means...THE TRUTH.

 

[HammerNoMore]

Boga once bubbled...
I'm thinking about buying a new computer.
Anyone knows any Air Integrated Computer that says yor ATR is 0 when it reaches 0 BAR?, that means...THE TRUTH.

That would be far from the truth. You will no longer be able to breath off the tank before you get to 0 BAR. Producing a computer that told you you have air time remaining when you truely don't would be, IMHO, criminally negligent.

30 bar may be a little a little conservitave for you but you really don't want the computer to wait for 0 BAR to go to 0 ATR.

 

[DA Aquamaster]

My Sherwood Wisdom can be set to use an end pressure of 300 psi (20 bar) which is a little closer but still not 0.

In the past I used an Aqualung digital pressure gauge in the console with my non-air integrated computer. The digital SPG also figured air time remaining based on air consumption over the last couple minutes with an assumed end pressure of zero and no regard for the air required for ascent. In essence it just used a straight calculation to show that you will run out of air in X minutes based on the current psi per minute being used.

I suspect these features, or more correctly the failure of many divers to properly understand the limitations of these features, was the reason it was only marketed for a short time. Interpreting "1 minute of air time remaining" as one minute of "bottom time" at 140 ft, instead of what it really meant would in most cases mean an out of air situation for the clueless diver.

But for a diver with the smarts and experience to figure the air required for ascent from depth along with any deco, and interpret the ATR figure it provides accordingly, it would give you the results you want. Finding one could be a problem although you may still find one sitting on a dealer shelf somewhere or on E-bay.

A serious downside of the digital SPG was that it managed to take a really simple and reliable device (an SPG) and make it failure prone. Mine used to go through a couple batteries per season and I had to be very proactive in changing them as it would go from telling me the battery was just fine pre-dive to a total shut down during 1 cold water dive.

 

[DA Aquamaster]

James Goddard once bubbled...


That would be far from the truth. You will no longer be able to breath off the tank before you get to 0 BAR. Producing a computer that told you you have air time remaining when you truely don't would be, IMHO, criminally negligent.

30 bar may be a little a little conservitave for you but you really don't want the computer to wait for 0 BAR to go to 0 ATR.

In my experience with the 3 air integrated computers I have owned, all showed some fudge factor at the low end of the scale. When the spg says "0" zero I always had 100-200 psi of air left in the tank.

Also, with a high performance reg, you can suck a tank down to very low pressure indeed. With my Mk25 D400 I get the normal very good breathing performance right down to the point where the actual tank pressure equals the intermediate pressure. (This normally occurs a bit after the air integrated computer says "0"). I can then get several breaths off the tank that become successively harder until the reg no longer delivers air. At this point, there is not even enough pressure in the tank to run the LP power inflator at any useful rate. (Debunking another common misconception that that you can still inflate your BC when you can no longer get air through the reg.)

So in practice, with these two factors combined I can get another 5 minutes of air at 10' after my air integrated spg says the tank is empty so there is already some margin of error built in.

However I agree with you that a 20-30 bar safety margin is not a bad thing, and that deleting that margin of error would most likely get a computer company sued. (Which I would guess is what happened with Auqalung's short lived digital SPG.)

With an unbalanced first stage or low perfroming reg, a diver may well not be able to breathe the last 100-200 psi off the tank and the computer manufacturer has no way to control for this eventuality. I suspect this is why the fudge factor is built in to the tank pressure reading in addition to the 20 to 30 bar end limit.

 

[Lemonade]

It's not just a function of tank pressure. Computer takes into account that you need to ascent from the current depth at a safe rate with required stops and still have your reserve when you hit the surface.

So when you see 0 air time remaining it does not mean you have no air in you tank it means it directs you to start the ascent immediately.

Whether you want to rely on those air algorithms and estimates is the whole different story.

 

[sheck33]

too expensive, i love my SPG, simple, reliable and it doesnt need a battery. What do you need AI for.........