Will Air Integration in dive computers replace the SPG?

[Ghosty]

SPGs are a valuable tool. I can't see them going away.

Even though I have a computer w/ AI, I'm gonna also run an SPG just for trusted (and hosed) redundancy/safety. Can't hurt!

 

[KenGordon]

As far as I'm aware (and I'm familiar with most agencies syllabus), there is no recreational level diving course that qualifies to use more than one gas on a single dive. At most, they add an 'ideal ascent gas' that is for conservatism only and would be recorded as per bottom gas for the purposes of nitrogen tracking.

How about diving nitrox with a pony of air? Do people need a 'technical' course for that? Or http://www.bsac.com/page.asp?section=3635&sectionTitle=Accelerated+Decompression+Procedures which is a 'club' course?

Why do the manufacturers do it? Look at the recommendations given to new divers here. If a computer does not have gauge mode, user settable GF and black LEDs which light up black then it is obviously useless.

Training is the same. The idea of 'what do I want to dive?' leading on to 'what do I need to learn to do that?' seems rather lost here.

 

[stuartv]

Now, I don't know if WAI will replace the SPG in the future. I can certainly envision a future of diving where that could be the case. We had some good suggestions about what we would like to see from WAI. Does anyone else have any thoughts on the topic of the future of WAI?

Based on some of the earlier posts, I'm thinking their is still some room for improvement in the ATR algorithm.

For example: Right now, my Oceanic defaults to a setting of 500psi for a Reserve, which means that it displays an ATR that will show as 0 at the moment when I have enough air left to make a 30ft/min ascent, a 3 minute safety stop, breathing all the while at the same rate I have been for the past 90 seconds, and arrive at the surface with 500psi left.

But, as has been noted, if my buddy goes OOA at the same time my ATR hits 0, depending on how deep I am, the gas I have left may not be enough to get us both to the surface before I also go OOA. And that doesn't even factor in things like my buddy having a higher SAC than I do or that my SAC may go up when my buddy swims up signaling OOA.

I don't think it's reasonable to expect a computer to do an ATR that is based on some estimate of what a higher SAC would be. That is up to the diver to decide and program in as the reserve the diver wants to set.

But, what might be reasonable is for the computer to do some kind of sliding scale extrapolation to increase the planned reserve based on depth. For example: Let's say the diver accepts the default of 500psi for their Reserve. The computer might take that as the reserve if ascending from 60', and then do some math to automatically increase that number as you go deeper than 60', with an end result of, if, say, the diver goes to 130', the computer now bases the ATR on a calculation that includes arriving back at the surface with 1000 psi, instead of 500.

I'm not proposing a specific algorithm. I'm just throwing the general idea out there. Planning to leave the "bottom" in time to arrive at the surface with 500 psi might be fine, if you're only diving to 60'. But, if you're going to plan on leaving from 130', it seems like you might want to make your plans for leaving based on arriving at the surface with some higher amount. So, why not work out a reasonable algorithm and build that into the computer's ATR calculation. That would save the diver having to adjust their reserve setting for each dive based on their planned max depth.

Or, maybe just change the computer to have 2 reserve settings. One for 60' and one for 130' and let the computer interpolate a reserve number for any depth in between.

 

[CT-Rich]

ATR is like suggested serving size on the nutrition label. It is a convenient reference, but not really meant beyond being a suggestion. I like it because it tells me if I am working too hard (and breathing down my tank). I use it to plan my return (do I have air left to check this bottom feature out). It also gives me useful data about how I might want to continue the dive. I will have more time on the swim in if I follow the wall at 20 fsw versus my current 35, so I will be getting out at the landing instead of making a surface swim.

Could I survive without any of this data? Sure, but it makes diving more worry free because I am able to confirm what I already have in my head with what my computer is thinking. What you do with the data is upto you. I mostly solo dive, so I don't really worry about the other guy and I am realize those numbers are just numbers and if I feel the need to have additional air for a OOA buddy, I need to plan that and watch the ATR with that in mind. But I am yet to have a situation where I or a buddy have gone OOA.

 

[The Chairman]

PDCs are only tools but they're not the only tools. I can't remember if I shared this here, but if you are doing OW diving, go with 100psi/10ft. Remember, if you don't have the air to do a safety stop, then it's not safe anymore. It's OK to skip a precautionary stop under these circumstances: it's not mandatory, but optional. However, this is not an appropriate strategy for a deco dive.

 

[boulderjohn]

For example: Right now, my Oceanic defaults to a setting of 500psi for a Reserve, which means that it displays an ATR that will show as 0 at the moment when I have enough air left to make a 30ft/min ascent, a 3 minute safety stop, breathing all the while at the same rate I have been for the past 90 seconds, and arrive at the surface with 500psi left.

But, as has been noted, if my buddy goes OOA at the same time my ATR hits 0, depending on how deep I am, the gas I have left may not be enough to get us both to the surface before I also go OOA. And that doesn't even factor in things like my buddy having a higher SAC than I do or that my SAC may go up when my buddy swims up signaling OOA.

If in the circumstance you describe your buddy goes OOA when your ATR hits 0, you may not have enough gas for the two of you to do a safety stop, but you should have more than enough to get you both to the surface.

Different people have different opinions about gas reserve. Some would say you must reserve enough gas to get both you and the buddy to the surface with all stops completed. Others would point out that the safety stop is not required, so in an OOA emergency it is easily and safely dispensed with. Still others argue that the reason for the 500 PSI reserve is precisely for such a situation, and that 500 PSI reserve should be enough for your OOA buddy to do the safety stop with you.

 

[stuartv]

If in the circumstance you describe your buddy goes OOA when your ATR hits 0, you may not have enough gas for the two of you to do a safety stop, but you should have more than enough to get you both to the surface.

Different people have different opinions about gas reserve. Some would say you must reserve enough gas to get both you and the buddy to the surface with all stops completed. Others would point out that the safety stop is not required, so in an OOA emergency it is easily and safely dispensed with. Still others argue that the reason for the 500 PSI reserve is precisely for such a situation, and that 500 PSI reserve should be enough for your OOA buddy to do the safety stop with you.

The arithmetic has already been presented - in this thread, I think, but maybe in the SW AI thread. IF (that's a big if) you assume things like a 0.75 cu-ft/min RMV and that you and your buddy both double your RMV when the buddy goes OOA, then a 500 psi reserve might indeed not be enough for a safe ascent from 130'. Thus my thinking that a larger reserve would be appropriate for deeper depths. Thus why having the computer automatically use a larger reserve at deeper depths MIGHT be a nice feature.

Or maybe not. That's what this discussion thread is for, I think.

 

[guyharrisonphoto]

Hi Stuart,

Right now I do it manually. Diving an AL 80, if I am shallower than 90', I leave it at 500 reserve. For 90 to 120, I go to 700, and 120 or more, 800--I set it for less if I am on an HP 100 or 120. Maybe more if it is going to be a stressful dive (night dive in a strong current for example) Like boulderjohn said, in a rec diving gas sharing emergency I am not doing a safety stop, as I expect my OOG buddy's first priority is to get to the surface. Similarly, I am heading up at 60'/min until I hit 30 feet when I will slow it down.

What you seem to be posing is a "rock bottom" algorithm, where the computer calculates ATR based on the gas needed for ascent based on two divers using the tank--i.e. double your current real time consumption at the current depth (the only one available to the computer), as predicted through the ascent (like current ATR algorithms). This would be "rock bottom" refined for the real-time conditions of the dive and would replace a pre-set "reserve". That might actually be a good option to offer, especially if you could program the parameters of the ascent (no stops, faster rate as I would do, or true "rock bottom" with standard ascent and the stop).

 

[agilis]

The arithmetic has already been presented - in this thread, I think, but maybe in the SW AI thread. IF (that's a big if) you assume things like a 0.75 cu-ft/min RMV and that you and your buddy both double your RMV when the buddy goes OOA, then a 500 psi reserve might indeed not be enough for a safe ascent from 130'. Thus my thinking that a larger reserve would be appropriate for deeper depths. Thus why having the computer automatically use a larger reserve at deeper depths MIGHT be a nice feature.

Or maybe not. That's what this discussion thread is for, I think.

Maintaining a larger gas reserve at deeper depths? Of course. That's what some people call a no-brainer.

If you need a computer to do this for you there is a problem somewhere.

 

[Bennno]

Stuff like 'rock bottom', turn pressure and max depth really needs to be determined before you enter the water.
Who needs a computer to tell you what your gas reserve should be?
This is solving a problem that doesn't exist.