Why the dislike of air integrated computers?

[Searcaigh]

I have a power block (charged by USB or Solar) for when I need to recharge my phone, tablet or PDC and power isn't immediately available. To Solar charge the block takes around 6 hrs

Given on a liveaboard I need to charge my camera, my iPad, maybe my Mac book solar cells don't really cut it unless the boat was covered in them, maybe with a wind turbine on top and hauling a water turbine

You have just gone power crazy

BTW I am not sure where that monkey is, you may have misspelt something

 

[stuartv]

I bought an Oceanic Atom 3.0 in December. It came with the wireless transmitter and the data download cable. All brand new, from my LDS, for $550. They MAY even still have some at that price. I haven't checked in a few months.

I really could not be happier with it. The WAI has worked flawlessly. The data, particularly regarding my RMV, is very educational to look at once downloaded to Subsurface. I really like the wristwatch form factor. I rarely whack it on things (diving or during an SI) because it is so small/low profile. I have masks with reader lenses in them so reading it easily is no problem. Without reader lenses, I can still read the big numbers - I just can't read the smaller print of the labels that tell me what each number is. But, when I was originally diving it with no reader lenses that wasn't a problem because it was always pretty obvious to me what each of the numbers was without needing to read the labels.

It supports 3 gases, though I'm not sure when I'd ever take advantage of that. On a Rec dive, I'd only ever have a second gas if I were to take a pony bottle. And if I'm using the pony, that means I've run into an emergency situation and I'm just concentrating on getting to the surface. Not sure I'd be bothering to do a gas switch on my computer at that point.

And if I were doing a Tech dive, I'd be using a computer with proper tech diving features, so still not relying on the Atom for anything related to gas switches.

Also, the Oceanic/Aeris family of computers generally seem to be among the most liberal computers (for NDLs, on repetitive dives) out there - if you choose to use the more liberal algorithm. I did 2 dives last Sunday. First was to 112'. Total dive time was something like 38 minutes, with an average depth around 77'. I had a 1 hour, 34 minute surface interval, then did the next dive, which happened to be almost the exact same profile. My computer gave me enough NDL on the second dive that I still ended up with an EDT of 31 minutes or so (IIRC), with the same max depth and approximately the same average depth.

I haven't ever heard anyone claim that the Oceanic algorithm is so liberal as to be unsafe. So, I really appreciate how much bottom time I got on Sunday and am glad I was not using a more conservative computer. From the research I have done, I believe that there are a number of other popular computers out there that would have probably given me a bit less NDL time on the first dive and a fair bit less on the second dive.

If you are shopping for a computer and looking at the Atom, be aware that the Atom 3.0 and 3.1 only have one difference. The 3.0 has the Buddy Check feature. The 3.1 had that feature removed due to a patent infringement lawsuit. That is the only difference between them. Yet the 3.0 can be found for cheaper (if it can be found at all) because there is a "newer" model out that superseded it.


For the record, I also have an Aeris A300 XT console (computer, SPG, and compass) which I dive with as my backup. I like knowing that, if my primary computer fails, having my backup computer along on every dive means I could finish my current dive and continue on with my next planned dive and my backup computer would have all the same tissue-loading info as the primary, so I would not have to be guessing about the tissue loading I took on during the dive where the primary failed. And, conveniently, the A300 uses the same algorithm as the Atom, so I don't get issues where I'm fine according to the Atom, but I'm in deco according to my backup. It seems to me that, if you dive with two computers, you should be following the NDL of whichever one is most conservative. Though maybe that's really not such a big deal for normal Recreational diving. I do know that my dive buddy last weekend had 3 computers. One of them went into deco on one of our dives. He hung on the line long enough to let that one clear before we got out, so that he wouldn't get hassled for violating a deco stop by a mate or the boat captain when we got back aboard.

---------- Post added July 30th, 2015 at 11:57 AM ----------

There are several recent posts expressing concern or even dismay at the sad state of affairs when it comes to divers and their dive planning, and especially gas management. I believe this entire thread is presumed to be in the context of Recreational diving. I mean, nobody is really, seriously trying to debate the use of WAI in Tech diving, right?

So, when you are talking about Rec diving, why do you (those of you that do) think dive planning and gas management is such a big deal?

I mean, for just about every one of my 35 dives, so far, the dive plan and gas management has been the following:

Me: "What's the max depth here?"

DM: "X"

Me: "Okay. The dive plan is to get in and swim around and go no deeper than X. Then get out before we run out of NDL."

Me: "The gas management plan is to be back on the boat with 500 psi left."

Or, occasionally:

Me: "The gas management plan is to be back to the anchor line and starting the ascent with 1000 psi left."

I don't really consider that to be real dive planning and gas management planning. Yet, it seems perfectly adequate for Recreational diving. So, are you saying there should be more to it than that? If so, what and why?

If my normal planning and management is adequate, then I definitely don't see how WAI is dumbing things down compared to having a HP hose with an SPG - and even using tables instead of a DC. With tables and an SPG, I could look up the max depth on a table, to get the NDL, before I get in, and then set a dive watch to count down that much time. I suppose you might consider that "educational" and, thus, desirable for people to do. Even with that, I would still just be getting in and watching a countdown timer and my pressure gauge/readout to make an on-the-fly decision about when to ascend and get out. Same as if I am flying a WAI DC.

Anyway, planning with tables versus flying a computer is kind of a different discussion that what this thread is about. Air integration versus a dedicated SPG doesn't really seem like it really makes any significant difference to how someone would dive - other than AI *possibly* making the dive a little safer, in the case it tells the diver to get out sooner because the computer has figured out the diver is going to run out of air.

 

[KenGordon]

Me: "The gas management plan is to be back on the boat with 500 psi left."

Or, occasionally:

Me: "The gas management plan is to be back to the anchor line and starting the ascent with 1000 psi left."

I don't really consider that to be real dive planning and gas management planning. Yet, it seems perfectly adequate for Recreational diving. So, are you saying there should be more to it than that? If so, what and why?

How do you know when to leave the bottom to be back on the boat with 500psi? It will depend on your depth and SAC.

 

[stuartv]

How do you know when to leave the bottom to be back on the boat with 500psi? It will depend on your depth and SAC.

Well, I *don't* do it by actually calculating anything before I get in the water. As I was saying, I don't feel like I'm really doing dive planning and gas management planning. Yet it seems to be working out just fine.

Generally, I just monitor my SPG, depth, and NDL. Lately, I've been running out of NDL well before I have any concern about getting low on air. But, if I were using an AL80, that wouldn't so much be the case. In which case, I'd be aware of my depth as my SPG got below half a tank. I would know that from, say, 120', it would take me 4 minutes for an ascent and 3 minutes for a SS, so 7 minutes to get out. Based on watching my time and SPG, I'd estimate (more or less by gut) what my pressure should be when I start my ascent. For a dive to 120, I would expect it to be somewhere in the 1000psi range that I would want to start ascending. From 60', probably more like 750'ish. But, like I said, it would really be by guesstimate based on how fast the first part of the tank went down. And knowing that if I'm off by a bit I have a 500psi margin for error.

When I type that all out, it sounds a bit risky. Maybe even dangerous. But, it seems to be pretty normal - at least, in my limited experience on the 11 or so boat trips I've been out on. So, that's what I'm asking: What more do you really suggest a diver getting in for a "normal" Recreational dive do? The way "everybody" seems to do it seems to have a pretty good track record...

 

[boulderjohn]

The steps required to plan a dive depend upon the nature of the dive and what the diver hopes to accomplish. What is wholly necessary on one dive will be inappropriate on another. Unfortunately, a lot of people either do not realize that, or they do not accept it. I have seen many threads on ScubaBoard in which people insist that there is only one way to plan a dive, and if the way you did it on your dive does not match that one way they know, than the dive was unplanned. For many, that one way is to go to a certain planned depth and stay there for a specific amount of planned time. That works fine for some dives--not so fine for others.

 

[drrich2]

Stuartv:

There are some on this forum with what I'd call a subculture of independence, with the view that you should always 'own your dive,' in the sense that even on guide-led tourist excursions you should be independently navigating, always know where you are, have rock bottom (or similar) gas calculations planned in your head, etc...

Which I suspect only a very small minority do. If I fly to New York & need to get around, I'll probably take a cab. And not sit in the back seat with a paper map trying to 2nd guess the cabbie. Similarly, I defer to professionals guiding in areas they're seasoned in and I'm new to, and maybe only dive once in my life. Especially in a guided group where the guide's dive plan has to be conservative so everybody gets back with gas. You still monitor your own depth, gas & NDL. The navigation is just one example.

Another issue, whether boat or shore diving (e.g.: Bonaire), is that many of us don't know the underwater topography of the site well enough for multi-level dive planning in detail, even if we planned on it. We may enter with a max. depth in mind, but average depth may vary considerably. So diving with a rough plan (e.g.: max. depth, don't violate NDL, a turn pressure in mind, a planned rough amount of gas to exit with) is common practice.

This sort of planning is apt to occur in excellent conditions on rec. dives. If you're diving very deep, dark & cold, in current, and there are other complications, then you have to rethink.

The amount of detailed planning one 'should' do for undemanding rec. dives in benign conditions has historically been a contentious topic, but people vote with their feet, and you see that on dive boats & shores.

Richard.

 

[Dr. Lecter]

I would think a solar cell, would be useful to just extend the battery life, not completely eliminate the eventual need - or capability to replace the battery.

Why would anyone want the engineering necessary for that ultra marginal benefit? AA batteries are incredibly cheap, and if you can't reliably open and close a single o-ring sealed compartment every couple months you have problems.

 

[rivers]

There are several recent posts expressing concern or even dismay at the sad state of affairs when it comes to divers and their dive planning, and especially gas management. I believe this entire thread is presumed to be in the context of Recreational diving. I mean, nobody is really, seriously trying to debate the use of WAI in Tech diving, right?

So, when you are talking about Rec diving, why do you (those of you that do) think dive planning and gas management is such a big deal?

I mean, for just about every one of my 35 dives, so far, the dive plan and gas management has been the following:

Me: "What's the max depth here?"

DM: "X"

Me: "Okay. The dive plan is to get in and swim around and go no deeper than X. Then get out before we run out of NDL."

Me: "The gas management plan is to be back on the boat with 500 psi left."

Or, occasionally:

Me: "The gas management plan is to be back to the anchor line and starting the ascent with 1000 psi left."

I don't really consider that to be real dive planning and gas management planning. Yet, it seems perfectly adequate for Recreational diving. So, are you saying there should be more to it than that? If so, what and why?

If my normal planning and management is adequate, then I definitely don't see how WAI is dumbing things down compared to having a HP hose with an SPG - and even using tables instead of a DC. With tables and an SPG, I could look up the max depth on a table, to get the NDL, before I get in, and then set a dive watch to count down that much time. I suppose you might consider that "educational" and, thus, desirable for people to do. Even with that, I would still just be getting in and watching a countdown timer and my pressure gauge/readout to make an on-the-fly decision about when to ascend and get out. Same as if I am flying a WAI DC.

Anyway, planning with tables versus flying a computer is kind of a different discussion that what this thread is about. Air integration versus a dedicated SPG doesn't really seem like it really makes any significant difference to how someone would dive - other than AI *possibly* making the dive a little safer, in the case it tells the diver to get out sooner because the computer has figured out the diver is going to run out of air.

My gas management plan: minimum gas. How much gas do I need to get myself and my buddy back to the surface (or first available gas source), including any and all stops (whether a min deco dive or a dive with mandatory deco)? What that pressure is depends on the dive. If it's shallow, it may be 50 bar in twin 12s. A bit deeper, could be 70bar. Mandatory deco on back gas only, could be 100 bar.

My general dive plan: Jump in, swim around, come back up again. We may not have a set bottom time, as it depends on conditions in the water. Generally speaking, the skipper gives a max allowable total dive time (normally 70-90 minutes surface to surface depending on the site. Longer for deeper tech stuff). For sea dives in the 30m range, we generally say our bottom time will be between 30 and 45 minute, Deco schedule depends on bottom time. We don't know what we will do for a bottom time until we get down there.

 

[guyharrisonphoto]

How do you know when to leave the bottom to be back on the boat with 500psi? It will depend on your depth and SAC.

That's why AI computers are a big safety advantage for rec divers, and the less experience they have or gas planning they do, the more the computer adds to their safety. All they do is plug into the computer that they will want to be on the surface with "x" psi (call it 500 for discussion sake). Since 500 is an almost universal standard for rec diving, they probably only have to enter it once and then forget it. The computer takes into account depth, including multi-level profiles that cannot be "calculated" easily by hand even for experienced divers. The computer takes into account real-time SAC at all stages and depths of the dive (most sample every 10 to 30 seconds), and so accounts for high effort versus low-effort dives. The computer takes into account cylinder volume (no need to program that in), because the calculation is based on change in pressure over time and so accounts for large versus small volumes of gas. The computer does all of this and "tells" the diver when it is time to begin the ascent in order to reach the surface with the desired psi left.

These calculations are done with a much higher degree of precision, based on the real conditions of the dive, than even "doing the math" on paper would allow, were that even possible during the dive. It is much better than "come up at 750" which is a completely rough estimate, and might be too much for some, and too little for others.

So, you might be "flying the computer" but that, actually, is a very precise method of gas management, just like it is for managing NDL, especially on multi-level profiles.

 

[Dr. Lecter]

The computer takes into account cylinder volume (no need to program that in), because the calculation is based on change in pressure over time and so accounts for large versus small volumes of gas.

Please tell us all more about these magical devices that can sense what size tank you're diving....

Spoiler: sorry kids, it's really important to program an accurate cylinder volume if you want to rely on an Air Time Remaining calculation you don't understand beyond 'the expensive glowing box says I'm OK!'