AI question - dive time remaining

[fnfalman]

Air-integrated computers are still dependent on battery power. I'm surprised that you are asserting that an electronic gizmo is more reliable than an analog SPG. :shocked2:

Which is a more reliable vehicle? Easier to start up and have less broken parts?

Honda Civic 2010 or Ford Model T?

 

[fnfalman]

What would it do if the reserve is set to 1500 and you are at 20 feet with 1300 psi remaining? Does it get upset?

I'm not a fan of AI (as you can probably tell! ) Just not applicable to much of my diving,but each to their own.

Yes, the computer gets upset and locks you out and you can't dive for five days afterward. It will even email mommy and let mommy knows that you've been a bad diver too.

An alarm goes off. You're free to ignore it. I don't have an Atom 2, but my D9 allows me to disable all audible alarms, which I do, so I don't annoy myself or my fellow divers.

I only have two dive computers (Sherwood Wisdom 2 and Aeris Elite T3). They both let me shut off the audible alarms. And yes, I do shut them off because I can actually see the blinking red alarm light, and yes, I hate hearing these annoying beeps underwater and I don't want mine to upset other divers who may not take kindly to unnecessary noises while diving.

So far the only thing that bothered me was that I couldn't disable the RGT number on the AI computers that I used. That number is pretty meaningless in my opinion. I'd rather see a bigger raw pressure indicator, or perhaps actual SAC rate.

You are free to ignore the countdown timer. But I have yet to see an AI computer that doesn't have the pressure reading prominently displayed. SAC is shown afterward or after downloading the file. I agree that it would be nice to have SAC rate available at a touch, but I figure you can calculate that quickly since that you have bottom time remaining AND pressure readout.

 

[FritzCat66]

No, actually, I was explaining what I thought Ian's criticism was.

Noted, and I apologize for directing that at you.

Actually I think keeping an appropriate gas reserve for you and your buddy is easily accomplished with a little mental arithmetic or some simple rules of thumb. You might need a crystal ball to accurately predict an emergency, but to anticipate one, all you need is a little training and experience.

Now, how do you think the AI computer's reserve pressure gets set to begin with? It's not an automatic computer function: the diver has to use exactly the method you mention - "a little mental arithmetic or some simple rules of thumb" - in order to set it to begin with for whatever is anticipated. If something happens even beyond what was anticipated, they'll have to recalculate things on the fly, but the AI computer will be displaying all the same information a non-AI computer would be displaying in order to facilitate such on-the-fly decisions, so I still don't see how any of these criticisms of AI technology apply.

How is the DTR data useful if you have to constantly back out a gas reserve? It doesn't simplify anything. It's easier to just look at your gas supply.

How does it NOT simplify things to have your remaining dive time calculation already considering your own pre-programmed reserve (and, with some, deep stop & safety stop times included as well)? Even if you're doing it in your own head, isn't that basically what you're determining, i.e. "how much longer could I stay here given all the variables and my intended reserve"? How is it not simpler for the computer to make that calculation for you?

I suppose trying to use the computer's DTR would perhaps complicate things if you intend something like holding a reserve at the beginning of the dive but then deciding to go ahead and use it into the dive when it turns out you're not needing it - but if so, is that really a reserve?

On top of that, what AI computer doesn't display actual cylinder pressure as well as DTR? So if you're changing things on the fly, you can still do that, and disable or ignore your reserve pressure alarm. So the AI technology seems to offer the advantage of having all the data you need - whether you use it all or not - moreso than any other single instrument.

I've been using AI since it was introduced, in the early 1990s, and continue to do so. There is nothing "newfangled" about it to me. I am glad you have finally discovered it. After a while you might have a more objective view of its limitations.

Oh come now, playing the "condescending old veteran" card rarely helps anyone's argument. But I do apologize for any implication I was calling you an "old hayseed".

 

[RJP]

Not sure about all of them, but a good AI computer will complain if your current dive plan will run you out of air before getting you out of the water.

Which "good" computer knows what your dive plan is? I know of very few, none of which are AI.

Setting turn pressures and alarms is not the same as "knowing what your dive plan is" nor is simply having a display that shows the shorter of remaining air time or no-deco time.

Lastly, assuming it could know your plan, what good is a computer that complains that you don't have enough gas remaining to safely get to the surface and/or fulfill your deco obligation?

 

[Leisure Proski]

AI Transmitters or hosed Computers with AI not only send the computer module cylinder pressure, but it gives you your air consumption rate. It does this by measuring the pressure drop over a given period of time letting you know in “Dive Time Remaining” how long your tank will last at your present depth and breathing rate. If either you’re breathing rate or depth changes the computer will then re-calculate your new breathing rate and up-date your Dive Time Remaining information. If your no-decompression time is less than your air time remaining that information will be displayed. In other words whichever is the shortest time reaming will be the one the computer will display. The feature of air consumption can help you better pace yourself when you dive this can increase your bottom time by keeping a more constant and deliberate pace. With a transmitter you eliminate a hose for a pressure gauge. You can wear the computer in a wrist boot or on a retractor. Is it worth getting a computer with a transmitter? Yes it once again eliminates a hose making you more streamline in the water and the benefits of knowing air consumption and working on improving it will create a safer and more efficient diver.

Leisure Proski

 

[vladimir]

Now, how do you think the AI computer's reserve pressure gets set to begin with? It's not an automatic computer function: the diver has to use exactly the method you mention - "a little mental arithmetic or some simple rules of thumb" - in order to set it to begin with for whatever is anticipated. If something happens even beyond what was anticipated, they'll have to recalculate things on the fly, but the AI computer will be displaying all the same information a non-AI computer would be displaying in order to facilitate such on-the-fly decisions, so I still don't see how any of these criticisms of AI technology apply.

You do realize that your gas reserve requirements change as you ascend, don't you? So there is no way to set it pre-dive and have it be applicable throughout the dive--rendering the DTR data useless, in my opinion. Which is why I ignore it. Yes, you have all the data that a non-AI computer gives you, but DTR is prominently displayed. I would prefer to use the limited display area more efficiently.

I suppose trying to use the computer's DTR would perhaps complicate things if you intend something like holding a reserve at the beginning of the dive but then deciding to go ahead and use it into the dive when it turns out you're not needing it

Exactly!!:lightbulb:

but if so, is that really a reserve?

Of course it is. Do you think you need the same reserve once you've ascended to 30' as you did at 130'? Here's a good article on the topic.

Oh come now, playing the "condescending old veteran" card rarely helps anyone's argument.

Unless you use it to trump an "old Luddite" card.

 

[Bubbletrubble]

Yes, but the pairing process consists of pressurizing the regulator with the wrist unit nearby. If it's on your wrist, it's hard not to pair it.

@vladimir: Can this be done underwater? The situation I'm thinking about is if you had to shut off your tank valve underwater...and then turn it back on again. I would think that the wireless system would be capable of this.

I suppose I have just heard and seen, on several occasions, people having problems with pairing up a hoseless AI wrist computer with the transmitter (on the surface). The "price" of these problems in several instances has been not being able to dive. In my limited experience, reliability of SPG (from greatest to least) is as follows:
analog SPG > AI computer (hosed) >> AI computer (hoseless)
Perhaps I just lack the experience that you and Netdoc have. I don't know.

Which is a more reliable vehicle? Easier to start up and have less broken parts?

Honda Civic 2010 or Ford Model T?

@fnfalman: Frankly, I don't see the usefulness in making that analogy. An analog SPG is not reliant on a capricious wireless connection. I love using technology. I'm a gadget freak, yet give me the choice between an analog SPG vs. a wireless/hoseless AI wrist computer...and I'll choose the analog SPG every time. In this case, I think older technology is more reliable than newer technology.

Perhaps a better analogy might be choosing between a BMW 3 series 2010 or a Honda Civic 2010. Which car do you think will be in the shop more in the first 10 years of ownership? Which car do you think will cost more in terms of repairs? Which car costs more to begin with?

P.S. I apologize to the OP for getting the conversation a little off-track. Perhaps our discussion, though, has brought up critical issues that a novice diver should consider when making gear choices.

 

[FritzCat66]

You do realize that your gas reserve requirements change as you ascend, don't you? So there is no way to set it pre-dive and have it be applicable throughout the dive--rendering the DTR data useless, in my opinion.

OK, OK... difference in dive style and reserve method then. I always dive with a pony, which is my real emergency supply and is totally separate from the AI computer^*. I give myself a fixed margin in my primary cylinder, maybe a bit more if I'm buddied up (although I expect them to mostly deal with their own reserve & bailout, and besides, I'm strictly rec so they're supposed to be able to handle a CESA). So the fixed reserve thing - and thus the AI computer's DTR - actually works pretty well for me.


^*Yes, I'm fully aware that means if I use it, my computer's calcs will be off for subsequent dives. Way off, because the pony always has plain air, while the main is almost always nitrox. But if I'm having to use that thing, something really bad is happening and I'm more worried about just getting to the surface alive than I am about subsequent dives.

Unless you use it to trump an "old Luddite" card.

LOL! That it might... but I'll let you tangle with them on that score.

 

[TSandM]

You know, I rarely say anything like this, but the picture I get here is someone wanting to swim along rather oblivious to the process of their dive, looking at their wrist from time to time to see how much longer they can do that.

I've never found it difficult to figure out how much longer I could be in the water, just going on my pressure alone. Combining that information with the NDL display on the computer got me out of the water in a reasonable way for a couple of years, before I started doing even more for myself.

In the five years of diving that Peter and I have done, we have never called a dive because of an SPG problem. They do sometimes begin to leak at the spindle, and I do the dive anyway (note this does not refer to cave/tech dives) and replace the spindle when I get home. I keep a couple of them around -- they are very cheap and easy to replace.

Of course, we have never called a dive because Peter's wireless AI failed to sync -- although it periodically does. But since he has an SPG backup, we dive anyway.

My personal view is that having my pressure on my wrist would be a small convenience with a big price tag, which would include periodic major annoyance.

 

[vladimir]

@vladimir: Can this be done underwater? The situation I'm thinking about is if you had to shut off your tank valve underwater...and then turn it back on again. I would think that the wireless system would be capable of this.

Good question. I have never tried it, and the manual gives no indication. In its description of the pairing process it does not preclude doing it underwater or specify that the computer must be in any particular "mode" to pair, so I would guess you could do it underwater, but I wouldn't bet heavily on it.