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bwildcat
07-13-2009, 16:50
I'm sure this is a question that's been asked 100's of times, but all of the answers I've read seem to wander off the trail somewhat...and then again, maybe it's just me.

If air-integrated computer algorithms can't be adjusted to individual tolerances, and there is such a range of opinions on the scientific basis of gas/tissue storage for the various algorithms used, then why is an air-integrated computer considered to be so "cutting edge"? And why is the cost so high compared to a non-air integrated computer?

Non-air integrated computers are just a digital indicator of standard dive table information as applied to your current dive, but without actual air consumption stats, right?

Air-integrated computers just add the real time data of actual air consumption, and then "project" some form of possible future air consumption - a regression analysis essentially, but with widely changing variables, like depth and breathing behavior.

But the 5 or 6 available algorithms used in dive computers are written using widely varying tolerances (in order to cover all types of bodies and physical conditions, and for liability reasons no doubt), AND more importantly, are based on some very different science interpretations of what the body is really doing to store and release the gases it builds up.

Most divers don't really have an in-depth understanding about most of this, and yet a whole range of air-integrated dive computers are available, and are typically a lot more expensive than non-air integrated computers. Why?

I understand the sales logic perfectly, but the underlying cost/benefit analysis has always been seemed fuzzy to me. Or am I just over-thinking the whole issue?

CompuDude
07-13-2009, 17:11
You're overthinking it, BY FAR.

Air-integrated has nothing to do with the decompression algorithm in question. All AI means is the computer monitors the gas pressure remaining, and logs the data. That's it. It also does a linear calc to see how long the gas will last, at the current depth and at the current rate of breathing (in other words, as long as NOTHING changes), but that's basic math a reasonably bright 6th grader could do, not something that has anything to do with the algorithm chosen to calculate NDLs.

They charge more for AI because (a) it costs them more to put it in (not necessarily the amount more that they charge, but that's capitalism), and (b) they can. (that's capitalism)

Exception: Uwatec has put some limited functions in their basic algorithm, which essentially claim to monitor the rate of breathing. If you start breathing harder, (recalling how the pressure sensors work, this just means that the rate of pressure dropping has increased), it assumes you are working harder, and the computer uses a proprietary algorithm to shorten your NDLs, since presumably your hard work means you're absorbing more N2 and your dive limits should be shortened up a bit. This has yet to be proven, and all it does is shorten your dive time, but again, all they can measure is a pressure drop and rate at which it's dropping... the computer has no idea how much gas you're actually consuming, and thus can make no effort to tailor something to an individual. Also, this is fuzzy science that is unproven and NOT peer-reviewed in any way, so in all likelihood, it's just marketing, in the end. A shorter dive is a safer dive, I guess... no one can argue with that.

bwildcat
07-13-2009, 20:23
I disagree with your first sentence, completely. Fact: every air integrated dive computer typically utilizes one of four commonly used algorithms to generate NDL's given current air pressure and depth. The link below provides some info on this.

Dive Computer Secrets Revealed | Scuba Diving Magazine (http://www.scubadiving.com/gear/2006/10/dive-computer-secrets-revealed)

But your overall point is well-taken. It's not a regression analysis, but just a simple linear calculation at a single point in time, instead of a statistical "averaging" over a defined period of time. AI computers are using air pressure and depth vs. non-ai computers using time and depth to calculate estimated NDL's. Is an AI computer really better than paying attention to your own diving characteristics and depth and pressure gauges, with perhaps a back-up non-ai computer?

My real point of all this is that none of it has been vetted scientifically at all. The four common algorithms have vastly differing ideas of whats going on in the human body regarding tissue/gas storage and release. Currently available microprocessor technology easily provides for a real time regression analysis, i.e. changing pressure, changing depth, and passage of time to predict the next NDL, and yet this isn't really utlized due to liability issues and a very large measure of scientific uncertainty.

And none of this is really explained by any dive computer mfger at all. The suggested marketing concept is that AI computers are an exponential evolutionary step in diving technology, which is pure BS.

Thanks for the input.

Splitlip
07-13-2009, 20:57
Interesting first post.

ianr33
07-13-2009, 21:05
I disagree with your first sentence, completely. Fact: every air integrated dive computer typically utilizes one of four commonly used algorithms to generate NDL's given current air pressure and depth.

The NDL (No DECOMPRESSION Limit) has NOTHING to do with how much gas you may or may not have left.
Call it "Time remaining before ascending" or whatever else you want but please not "NDL"

Splitlip
07-13-2009, 21:17
I think CD tried to explain that. He ain't hearing it. As I said, interesting first post. LOL

IndyDiver
07-13-2009, 21:57
I'm having a hard time thinking about this thread over the din of my troll alarm going off.
So I think I'll just :smilie40:

navyhmc
07-13-2009, 22:27
Simple: Air integrated does two things for you that a non-AI doesn't: It is a SPG and shows your PSI/BAR remaining. It will also show an estimated air time remaining at the current depth and the current psi/bar per minute consumption. Additional Alerts may also be included to give an alert when your air is at a selected PSI/BAR or you estimated air time remaining goes to or below a selected time. Other than that, a AI and a non-AI work the same IRT that specific manufacturers algorhythms for NDL and deco.

Jack Hammer
07-13-2009, 23:44
Simple: Air integrated does two things for you that a non-AI doesn't: It is a SPG and shows your PSI/BAR remaining. It will also show an estimated air time remaining at the current depth and the current psi/bar per minute consumption...
There's a third thing it does for you which I personally find the most appealing of all it's fancy bells and whistles...




...it records you starting and ending pressure for you so when you forget to write it down you can look it up later.

Jack

navyhmc
07-13-2009, 23:51
True...I forgot about that. To me it's a good backup on that, I have that committed to memory eons ago.

CompuDude
07-14-2009, 00:40
I disagree with your first sentence, completely. Fact: every air integrated dive computer typically utilizes one of four commonly used algorithms to generate NDL's given current air pressure and depth. The link below provides some info on this.

It's almost like you're trying to communicate, but you seem to have missed the point completely. :smiley13:

You're mixing up the AI aspect of the computer (it's ability to read tank pressure), with the decompression algorithm. NDL's are not related to "current air pressure". They are related to current water pressure (depth) and time... that is all. The tank pressure and no-decompression limits have next to nothing to do with each other, outside of the one situation I outlined in my earlier post.

I certainly do agree that decompression algorithms could be far better scientifically vetted and peer-reviewed.

eelnoraa
08-26-2009, 20:33
After reading all the post in this threat, I have another questions. If all dive computer do is just calculation of a some formula, and with AI, it just monitor the tank pressure. Then why some are nitrox ready some cannot be use with nitrox?? Is it that the manufacture purposely elimimate the nitrox formulas in lesser model??

navyhmc
08-26-2009, 20:52
After reading all the post in this threat, I have another questions. If all dive computer do is just calculation of a some formula, and with AI, it just monitor the tank pressure. Then why some are nitrox ready some cannot be use with nitrox?? Is it that the manufacture purposely elimimate the nitrox formulas in lesser model??

A good question. There is a more calculations needed for Nitrox vs. air. with a air computer, it is only making NDL/deco/nitrogen loading calculations for one specific gas, no matter what the depth or dive-every dive will be 21% air, 78%-79% nitrogen.

The Nitrox computer has to have a variable algorhythm for the various nitrox percentages. It's not that the lesser (air only) models have this eliminated, it's not incorporated to begin with.

At any time, nitrox can be used with an air only compter. The difference is that your NDL's will calculated as if you were on air and not nitrox. Some folks do this as it creates a bigger safety factor when diving on Nitrox.

Clear as mud?

Splitlip
08-26-2009, 20:54
After reading all the post in this threat, I have another questions. If all dive computer do is just calculation of a some formula, and with AI, it just monitor the tank pressure. Then why some are nitrox ready some cannot be use with nitrox?? Is it that the manufacture purposely elimimate the nitrox formulas in lesser model??
Good question. I'll defer to the geeks, but I suspect there is a chip or 2 involved with calculating for nitrox. Some coputers I have seen require rounding the 02 mix to even intervals only. Cost factor I assumed as there would be fewer calculations. Remember an air only only has to calculate one 02 mix. A nitrox computer calculates all the others.

Splitlip
08-26-2009, 20:55
Oh God. Navy beats me again. (hurt me sailor)

CompuDude
08-26-2009, 23:21
After reading all the post in this threat, I have another questions. If all dive computer do is just calculation of a some formula, and with AI, it just monitor the tank pressure. Then why some are nitrox ready some cannot be use with nitrox?? Is it that the manufacture purposely elimimate the nitrox formulas in lesser model??

It's not that they eliminated an inherent "feature", more that they (1) didn't add in the chip with the hardcoded Nitrox calculations and/or (2) didn't add in the extra programming needed to accommodate the Nitrox variations. Air calcs are standard and off-the-shelf that hasn't really changed much. There's also a lot less testing needed to test against one scenario vs. many, many possible scenarios (adding all kinds of mix percentage possibilities in the mix).

All these things add cost, at least, when you're still developing the product. Once the programming is done, it takes the same amount of time to download one program onto a chip as another... but if they want to recoup their increased development costs, they need to charge more. (plus, look, more money for them!)

Tassie Diver
08-27-2009, 02:34
... but if they want to recoup their increased development costs, they need to charge more. (plus, look, more money for them!)
I think you've really hit on it here. Nitrox computers use the same algorithm, it's just that the FO2 is not 79%. The only real difference is a function to allow the user to input the FO2.

Actually, I'm not quite right. Most of them will monitor PO2 and OTUs. So I guess the Nitrox computers are a little more sophisticated. Hence the higher cost.

Cheers

TD.

Geez I hate it when I contradict my own train of thought.

bealskt
08-27-2009, 09:30
You think it would be easy for them to have a running calculator for air consumption. Essentially, start at the beginning of your dive and have a running 5-minute air consumption average, then project that to the amount left in your tank, and relate that to the current depth. I've done some programming similar to this in college (I'm an electrical engineer) and it's not impossible, especially for a bright CS...

ScubaToys Larry
08-30-2009, 21:35
You think it would be easy for them to have a running calculator for air consumption. Essentially, start at the beginning of your dive and have a running 5-minute air consumption average, then project that to the amount left in your tank, and relate that to the current depth. I've done some programming similar to this in college (I'm an electrical engineer) and it's not impossible, especially for a bright CS...

That is exactly what the AI computers do, but not based on 5 minutes... based on what you are doing now... so if suddenly you turn into a strong current and start breathing heavy, in just the matter of a moments, you will see your available air time drop due to the increased breathing rate.

TJDiver
08-31-2009, 11:07
After reading all the post in this threat, I have another questions. If all dive computer do is just calculation of a some formula, and with AI, it just monitor the tank pressure. Then why some are nitrox ready some cannot be use with nitrox?? Is it that the manufacture purposely elimimate the nitrox formulas in lesser model??

A good question. There is a more calculations needed for Nitrox vs. air. with a air computer, it is only making NDL/deco/nitrogen loading calculations for one specific gas, no matter what the depth or dive-every dive will be 21% air, 78%-79% nitrogen.

The Nitrox computer has to have a variable algorhythm for the various nitrox percentages. It's not that the lesser (air only) models have this eliminated, it's not incorporated to begin with.

At any time, nitrox can be used with an air only compter. The difference is that your NDL's will calculated as if you were on air and not nitrox. Some folks do this as it creates a bigger safety factor when diving on Nitrox.

Clear as mud?

I think it's worth noting here that the "bigger safety factor" of using air calculations while diving Nitrox is only a "bigger safety factor" up to Nitrox DNE depths...110 fsw for EAN36 (36% O2) and 130 fsw for EAN32 (32% O2). If your dive site has a hard bottom less than these depths, then I guess it could be argued this practice provides an added safety margin. However, it would seem to me to be a poor practice, as over time it might become easy to "forget" when diving a location where it is possible to exceed Nitrox depth limits.

Jack Hammer
08-31-2009, 13:01
After reading all the post in this threat, I have another questions. If all dive computer do is just calculation of a some formula, and with AI, it just monitor the tank pressure. Then why some are nitrox ready some cannot be use with nitrox?? Is it that the manufacture purposely elimimate the nitrox formulas in lesser model??

A good question. There is a more calculations needed for Nitrox vs. air. with a air computer, it is only making NDL/deco/nitrogen loading calculations for one specific gas, no matter what the depth or dive-every dive will be 21% air, 78%-79% nitrogen.

The Nitrox computer has to have a variable algorhythm for the various nitrox percentages. It's not that the lesser (air only) models have this eliminated, it's not incorporated to begin with.

At any time, nitrox can be used with an air only compter. The difference is that your NDL's will calculated as if you were on air and not nitrox. Some folks do this as it creates a bigger safety factor when diving on Nitrox.

Clear as mud?

I think it's worth noting here that the "bigger safety factor" of using air calculations while diving Nitrox is only a "bigger safety factor" up to Nitrox DNE depths...110 fsw for EAN36 (36% O2) and 130 fsw for EAN32 (32% O2). If your dive site has a hard bottom less than these depths, then I guess it could be argued this practice provides an added safety margin. However, it would seem to me to be a poor practice, as over time it might become easy to "forget" when diving a location where it is possible to exceed Nitrox depth limits.
The generally accepted max depths for 32% and 36% are 111' and 95', respectively (at 1.4 po2). The deeper depths are generally recommended for deco only (1.6 po2) and should be avoided for recreational diving. :smiley20:

TJDiver
08-31-2009, 13:29
After reading all the post in this threat, I have another questions. If all dive computer do is just calculation of a some formula, and with AI, it just monitor the tank pressure. Then why some are nitrox ready some cannot be use with nitrox?? Is it that the manufacture purposely elimimate the nitrox formulas in lesser model??

A good question. There is a more calculations needed for Nitrox vs. air. with a air computer, it is only making NDL/deco/nitrogen loading calculations for one specific gas, no matter what the depth or dive-every dive will be 21% air, 78%-79% nitrogen.

The Nitrox computer has to have a variable algorhythm for the various nitrox percentages. It's not that the lesser (air only) models have this eliminated, it's not incorporated to begin with.

At any time, nitrox can be used with an air only compter. The difference is that your NDL's will calculated as if you were on air and not nitrox. Some folks do this as it creates a bigger safety factor when diving on Nitrox.

Clear as mud?

I think it's worth noting here that the "bigger safety factor" of using air calculations while diving Nitrox is only a "bigger safety factor" up to Nitrox DNE depths...110 fsw for EAN36 (36% O2) and 130 fsw for EAN32 (32% O2). If your dive site has a hard bottom less than these depths, then I guess it could be argued this practice provides an added safety margin. However, it would seem to me to be a poor practice, as over time it might become easy to "forget" when diving a location where it is possible to exceed Nitrox depth limits.
The generally accepted max depths for 32% and 36% are 111' and 95', respectively (at 1.4 po2). The deeper depths are generally recommended for deco only (1.6 po2) and should be avoided for recreational diving. :smiley20:

Yes, but I was speaking primarily of the absolute do-not-exceed depths, and the risks of using normal air settings in dive computers...or non-Nitrox computers...while diving Nitrox...just not a good practice in my opinion.

CalBearister99
08-31-2009, 14:53
Simple: Air integrated does two things for you that a non-AI doesn't: It is a SPG and shows your PSI/BAR remaining. It will also show an estimated air time remaining at the current depth and the current psi/bar per minute consumption...
There's a third thing it does for you which I personally find the most appealing of all it's fancy bells and whistles...




...it records you starting and ending pressure for you so when you forget to write it down you can look it up later.

Jack

Ha! That's probably been my favorite feature as well. I never remember to write it down going in!

p944
09-25-2009, 19:56
I dive with an air integrated hoseless computer, which has issue with wireless signal lost intermittenly, though rare. If I could go back and make purchase decision again, I'd get either air integrated or wireless, not both.

Just something to keep in mind before you make a purchase decision.

CompuDude
09-25-2009, 21:01
I dive with an air integrated hoseless computer, which has issue with wireless signal lost intermittenly, though rare. If I could go back and make purchase decision again, I'd get either air integrated or wireless, not both.

Just something to keep in mind before you make a purchase decision.

I have yet to see the computer that delivers wireless pressure but is NOT air integrated as well.

I'm guessing you had a point in there that didn't come out right...

p944
09-28-2009, 11:47
I dive with an air integrated hoseless computer, which has issue with wireless signal lost intermittenly, though rare. If I could go back and make purchase decision again, I'd get either air integrated or wireless, not both.

Just something to keep in mind before you make a purchase decision.

I have yet to see the computer that delivers wireless pressure but is NOT air integrated as well.

I'm guessing you had a point in there that didn't come out right...

ha... my point was I'd choose either
-air integrated computer with hose OR
-wrist computer, and a good old pressure gauge in console.

Draq
10-02-2009, 13:13
My family has 3 hoseless air-integrated computers and we have never had any issues with losing signals. Rarely, the link may be lost, but never for more than a few seconds and usually no one even knows it until they look at the downloaded dives in the software. This is true even though two of us are photographers and have strobes going off frequently during a dive.

It does seem more likely to occur if the computer or transmitter battery is getting low, but even there, the link may be lost a few times for a couple of seconds each over the course of a dive. Completely insignificant.

I suppose this could be brand dependent, but I have absolutely no desire to go back to a "hosed" computer.