No air integration in high-end and tech DCs . Why ?

[Dr. Lecter]

Dr. Lechter. My AI has, thus far, always functioned properly, so has the computer. Before I got AI, I knew a lot of people that used it and none of them indicated that a loss of signal was a sign of computer failure or affected the deco calculations in the slightest. Nor has it ever been reported to do this on any forum that I have ever visited, and we all know that such a failure would go viral all over the globe if it was actually happening. So no, a loss of a signal or pressure reading would not make the whole computer suspect.

It seems evident that, because any AI computer works just fine as a regular computer without a transmitter and without showing pressure, that it's "regular" computer functions are not affected one way or another by the AI.

You are confusing what can happen--what 99 times out of 100 happens--with what might be happening. Whether you want to admit it or not, you simply cannot be sure what caused an AI failure: simple loss of AI, or, something affecting more of the DC than just the AI function.

In this case, simpler is less risky and less system integration is less risky. For the same reason, I like to run my primary and backup electronics on my CCR off totally independent sets of O2 cells, wires, batteries, and computers: if one fails, it cannot affect the other because there's zero integration between the two systems. Thus, I don't have to worry that a problem with my controller system has somehow also affected my backup system.

If you think the risk is tiny enough that you're willing to dive an AI tech computer for your deco schedule, knock yourself out. I assume you have at least one backup ascent schedule, so it's just a question of whether a failure is an obvious one or one you dismiss as the AI just being on the fritz.

 

[scubadada]

Getting back to the OP, a recreational diver, this thread, as usual, has lost its way. I have dived an Oceanic VT3 since July 2010 without a single problem. I appreciate having my air consumption and calculated SRMV available for each dive. I dive a Geo2 backup computer and a SPG and have needed neither on any dive, but could. Liquivision had certainly moved over to the air integrated arena, perhaps others are to follow, you can't prevent progress, forever.

Good diving, Craig

 

[Dr. Lecter]

AI in rec diving, where you can simply end the dive and ascend if something goes wrong, and you have only one or two tanks to monitor, is NBD. The OP's question, however, was about tech computers.

You'll notice Liquivision has branded the Lynx as a rec computer and doesn't seem to be rushing to add their AI hardware to the Xeo or X1.

 

[Pullmyfinger]

In the end my question seems to boil down to this:
- do tech divers have no use at all for air consumption data in their digital logbook ?
- is there any hardware requirement that would make it impossible to use the same platform for a tec and a rec DC ?

No. I have no use for it.

 

[fnog]

I would like to thank everyone for the honest attempts to answer the original question.

To those who would like me to shut up and, instead of asking scuba questions on a scuba forum, go and design that hypothetical tec DC, I would like to say: sure why not. I just love to spend my life in design of useless and potentially dangerous equipment. Since my pal Lex L. is a bit broke lately, and I am a bit slow in the head from smoking Zissou's ciggies, just send me the numbers for the national lottery and the formula for the elixir of youth, and I will do it. :joke:

Some people seem to know that it is impossible to make a purely passive beacon, from their knowledge in radio and electronics, but do not want to give details and numbers in this forum. I understand: this is a bit offtopic, even though a forum on DCs will automaticly to be a bit technical (in the engineering sense). If you have a minute, I would appreciate that you PM this however. One can easily find articles like "A self-sustaining, autonomous, wireless-sensor beacon powered from long-range, ambient, RF energy ", but these indeed relate to transmission in air, not salty water, and to a strong RF power source, not a DC running on 10 grams of battery. How about ultrasound instead of RF ? Could that both transmit enough power and receive data ? Still, it appears simpler to use a fiber casing on the SPG with a few turns of non oxydisable loop antenna and capacitor on the inside. That would be decently sturdy and has no obvious reason to disturb the operation of the SPG (exploding capacitor ? oxyde reaching mechanical parts ?).

That two systems have to be totally separate to reduce risks is not convincing. The failure probability of separate systems that are correlated (for example: you bought your cells at the same time from the same provider) is not zero. Let me restate that: if you want to believe that it is zero so you can dive quietly and safely, than it IS zero. Freedom of opinion and all that...If those two systems have components with high risks, I believe that is better that both systems have access to that component. What if the O2 sensor on one circuit is gone, and the other has a battery problem or an electrical open circuit ? You wish you had wired all O2 cells to both systems then. The extra wiring compared to the separate systems situation does not add failure risks, it just reduces them. (Again: a hypothetical question. I have never approached a rebreather, mostly to avoid being bitten by the owners).

The discussion has advanced quite a bit since yesterday, so I would like to remind everyone that I am a rec diver with about 60 logged dives. My job and certifications outside of scuba are probably of little interest here. My question was only a naive attempt at undertanding the dive computers market and evolution, and I am quite satisfied with the answers so far. I am not here to question the principles of an activity that I do not even know, less to lecture anyone. I am just hoping for a thorough and rational answer. If you believe my question is absurd, I am ready to take it. Just explain why.

So far the best answer in my eyes has been summed up by J. Lapenta (even if he publicly accused me of raping the principal): minimalism and conservatism are in the principles. Because AI is not needed for safety or to perform anything essential to the dive, it is rejected as an extra distraction and failure point. Relying on the DC in itself is dubious and it is better to have tables with backups and redundant bottom timers. (correct me if I misunderstood that)

An other answer is that tec divers know their gas volume per minute rate under various conditions and have integrated in their guts a feel for their remaining gas, such that they need the SPG not for information but just for confirmation. That is less valid. They integrated that skill using tools (tablet, timer, SPG, depth gauge, arithmetics) and experience. Add another tool to the mix and those who learn tec may have it better and faster.

There is also a principle to electronics integration and it need not clash with those of tec diving. Could some of you then imagine, and accept after years or field usage by rec divers, using a bottom timer that has inside properly designed electronics for doing AI on all your tanks for 100$ extra, but simply use firmware that completely ignores those sensors ? It is a solution to reconcile both principles, but it does not promote an improvement of the quality and openness standards of mass market DCs by adopting features from tec. The rule of this game seems to be that features are introduced first with low quality in mass market DCs, and then much later adopted and maybe improved in quality and safety by niche tec equipment makers who will make expensive models, while the mass DCs are not improved in quality and left with version 0.2 of the feature. If that satisfies everyone, I will be just fine with that too.

 

[Larry7895]

Perhaps you need to better understand Tech diving. You seem to be looking for a response based on your perceptions formed from 60 rec dives. Tech diving by definition is substantially more risky. Because of this the more failure points you remove the safer you are. But even that does not fully define it. When you tech dive you also have to manage your task loading, you simply have to get to the info you need when you need it and not be distracted by anything else. Before I started down the tech path I used to have every gadget under the sun (I still love gadgets), but I've learned, and frankly feel safer, planning my dive and then diving my plan. I have a Shearwater, but it's only a back up itself. My slate and bottom timer are my primary tools. If you are 70 or 100m deep, inside a large wreck or cave unnecessary task loading could cost you your life. Planning your dive and diving your plan using tools such as a slate and bottom timer also reinforces the very discipline you need to apply to all aspects of Tech diving. So while these gadgets are not only unnecessary, they can diminish the discipline that is vital to safely completing tech dives. Hope that helps a little.
(BTW I have use a variety of AI while doing primarily rec dives and I can tell you it can find plenty of ways to fail on you, far more than I have ever experienced using brass and glass - one day I'm sure the technology will be there, but not yet).

Regards
Larry


Sent from my iPad using Tapatalk HD

 

[DevonDiver]

As a technical diver/instructor, I select and carry what I NEED. That's all. No conveniences, no fun gizzmos, no showy-offy..

I don't NEED an AI. I won't NEED an AI.

As for failures/redundancy: if something goes wrong, the dive is aborted. End of.. When that dive might have cost me $000's, and been cancelled because of an AI (that I didn't NEED) failure... the whole idea of using one seems very pointless.

A properly trained technical diver doesn't need AI.

 

[flots am]

Some people seem to know that it is impossible to make a purely passive beacon, from their knowledge in radio and electronics, but do not want to give details and numbers in this forum.

There's no such thing as a "passive beacon" it violates a number of laws of physics. All the devices that seem to do this are powered by something, even if the "something" isn't obvious. Underwater, the "something" that powers the beacon is either impractical due to being underwater, or requires more power than is available in a dive computer.

That said, if there were a demand and enough money, I'm pretty sure that someone could build a transmitter that was powered by radioactive decay, air pressure or something else, but there isn't enough demand and money, so it hasn't happened.

How about ultrasound instead of RF ? Could that both transmit enough power and receive data ?

No. You would need enough power to turn your immediate vicinity in to an ultrasonic parts cleaner, in order to power a pressure transducer and transmitter sitting behind you.

That two systems have to be totally separate to reduce risks is not convincing. The failure probability of separate systems that are correlated (for example: you bought your cells at the same time from the same provider) is not zero. Let me restate that: . . .it just reduces them. .. .

You're missing a huge distinction: Technical dives are planned, not flown.

There is an infinite reliability difference between a computer on your wrist that's calculating on the fly using sensors and a battery, vs. a computer sitting on your desk at home, that produced a printed plan last night, that is now taped to a wrist slate.

As a software engineer with 30+ years of experience and a moderate amount of embedded system development, I would never trust my life to a single consumer-grade computer, running software that's most likely only ever been validated by a few developers, running on a single battery, underwater.

You're looking for an expensive, difficult, unreliable and potentially dangerous solution to a problem that doesn't exist.

flots.

 

[Lorenzoid]

I would like to thank everyone for the honest attempts to answer the original question.

To those who would like me to shut up and, instead of asking scuba questions on a scuba forum, . . .

I think you got some pointed replies because you were perceived as not just "asking scuba questions" but arguing that companies like Shearwater SHOULD be making this product you envision. You received opinions but continued arguing why they should do it.

I for one am not going to spend time arguing points of underwater electronics engineering on a scuba forum, as there are clearly WAY too many considerations for such a discussion to reach any sort of useful conclusion, not to mention it's a niche I don't have much familiarity with. If you've got an engineering background, then one thing you understand is that nothing is as straightforward as it initially seems. If you envision 1000 engineering hours, it will almost inevitably end up taking 2000. It is not that the computer you envision cannot be designed and produced, but rather that it appears it is not worth it to the kind of manufacturer who squarely aims his product at tech divers and has already gone to great lengths to establish a reputation for a straightforward and highly reliable product.

 

[nimoh]

There's no such thing as a "passive beacon" it violates a number of laws of physics. Al the devices that seem to do this are powered by something, even if the "something" isn't obvious. Underwater, the "something" that powers the beacon is either impractical due to being underwater, or requires more power than is available in a dive computer.

That said, if there were a demand and enough money, I'm pretty sure that someone could build a transmitter that was powered by radioactive decay, air pressure or something else, but there isn't enough demand and money, so it hasn't happened.


No. You would need enough power to turn your immediate vicinity in to an ultrasonic parts cleaner, in order to power a pressure transducer and transmitter sitting behind you.

I think by "passive" he means not powered by an electrical power source such as a battery but rather through magnetic fields. Perhaps it is possible to make this work underwater, and perhaps it is possible to have the gas pressure in the tank passively change the magnetic field slightly to communicate gas pressure remaining to the DC. The main problem is that there is not really any demand for it since tec divers (in general, I'm sure there are outliers) have not expressed an interest in any AI, and have given no indication that they would use AI if only the sending units were smaller or didn't rely on batteries.

OP:
I think this is a reasonable question to ask here. As you have said, you are not a tec diver but have an interest in this technology. I would hardly suggest taking tec training in order to answer your question and hopefully you have found some answers.