Shearwater Perdix AI

[Lorenzoid]

Clearly you have not spent much time reading posts by members of the Authoritarian Divers Party (a secret society who fears technology, change or individualism in the scuba diving world and travels under various three-letter acronyms whose names (acronyms) I will not mention. They pray at the alter of Halcyon (a long dead right wing dive god) and worship all things Hogarthian (an ancient cult into weird forms of bondage using nylon webbing). Ultimately, these folks subscribe to the principle that "You must dive the vay vee do and you vill only use dive gear vee approve of...or you vill die!" They can at times be held at bay by holding up a PADI dive traininig book and chanting "air integration is God's will!" It is rumored that wrapping one of them in a poodle jacket BCD will cause them to do whatever you say and answer any questions put them. Unfortunately, doing this banned by various international treaties on enhanced interrogation.

I have put my life at risk by even revealing their existence, but if I can save you from imminent death by Perdix by doing so, then I must...

Long Live the Resistance!

The more open-minded diver might simply recognize that there are different schools of thought, they are all at least valid enough to be preventing any statistical difference in diver injury, and regardless of which school of thought each of us subscribes to, there may be a day when we want to dive with or otherwise work with someone who does it differently then we do, and it might be helpful to that end if we understood where the other person is coming from. But you're apparently a Solo Diver, so you can afford to be as closed-minded as the people you criticize.

 

[Kevrumbo]

. . . If I'm using it to do any of the math, may as well have it do it all. I can look at the remaining pressure and my current depth to do all the math myself, to sanity check what the computer says. And, for that matter, the math for remaining time at current depth is easier than the math for how much gas I need for the ascent, so why have the computer do the easy part of the math and leave the harder part up to me?

Obviously, none of it is hard. You don't need a computer to do any of it. But, IF you choose to let the computer do some, why not let it do it all? That's all I'm saying.

Then do a math example to show us you know what your Perdix AI will read for GTR on a recreational dive at 66ft, with half pressure remaining: AL80 tank vs HP120. Make it even easier, use 1 cu ft/min RMV and your choice of a gas reserve of zero or 500psi (do both cases if you can).

Derive the solution based on the way you explained SAC rates and RMV.
(See post 504)

 

[jd950]

1. I am only sometimes a solo diver. That designation just appeared when I joined the solo diver group. I often dive with a buddy or a small group and not infrequently, I dive with people I just met.

2. Lighten up. Some "tech" folks take themselves way to seriously in my opinion and can be dismissive of others who do not dive the same way or enjoy the same aspects of diving. Sometimes I find that attitude amusing and will, from time to time, poke a little fun at it.

Sorry my post touched an exposed nerve with you. Didn't mean to get your fundies in a twist. (That was a pun.)

 

[Kevrumbo]

1. I am only sometimes a solo diver. That designation just appeared when I joined the solo diver group. I often dive with a buddy or a small group and not infrequently, I dive with people I just met.

2. Lighten up. Some "tech" folks take themselves way to seriously in my opinion and can be dismissive of others who do not dive the same way or enjoy the same aspects of diving. Sometimes I find that attitude amusing and will, from time to time, poke a little fun at it.

Sorry my post touched an exposed nerve with you. Didn't mean to get your fundies in a twist. (That was a pun.)

Simply, @stuartv 's logic by extension is that on the surface or at constant depth, you would use air faster on a HP120 tank than on an AL80 -->quite sure the Perdix AI will not support that result.

Again, that's just like saying if you put a larger gasoline tank in your car, your fuel economy in miles per gallon will increase. Pretty sure your car's odometer and gas gauge will not support that premise either.

 

[stuartv]

2. Lighten up. Some "tech" folks take themselves way to seriously in my opinion and can be dismissive of others who do not dive the same way or enjoy the same aspects of diving. Sometimes I find that attitude amusing and will, from time to time, poke a little fun at it.

I thought your post was funny!

If @Lorenzoid 's point is correct about all the agencies being statistically "equal" in terms of diver injuries, then I wonder why some of the more "progressive" agencies don't wave that around as a huge flag. "Teaching only computers for diving and for nitrox (i.e. no tables at all, ever) is just as safe, statistically, as you more rigid or demanding agencies' programs!"

it's the same thing I come back to every time somebody tells a new diver they should stick to a computer with a more conservative algorithm because it's "safer". Really? Are there any stats to show that computers running DSAT are getting people bent more than computers running Weinke RBGM? If not, then how can you say that the difference is meaningful to the diver's safety? The longer bottom time is clearly meaningful to many divers' enjoyment!

 

[Joneill]

Simply, @stuartv 's logic by extension is that on the surface or at constant depth, you would run out of air faster on a HP120 tank than on an AL80 -->quite sure the Perdix AI will not support that result.

Again, that's just like saying if you put a larger gasoline tank in your car, your fuel economy in miles per gallon will increase. Pretty sure your car's odometer and gas gauge will not support that premise either.

Sorry - but you continually mis-characterize what was said:

And where did I EVER say that a given diver's RMV changes based on tank size? I said that a SAC of 25 means a lower RMV if you're using an AL80 vs an HP120. I didn't say a given person's RMV was going to change if they get a bigger tank. I said IF their SAC is 25 with an AL80, then their RMV is lower than IF their SAC is 25 with an HP120.

He was saying that someone measuring an SAC of 25 (psi/min) while diving an AL 80 would have a lower RMV (cu.ft./min) than someone measuring an SAC of 25 while diving a HP 120. Given that a full AL 80 has 0.026 cu.ft./psi (77.4 cu.ft. @ 3,000 psi) and a HP 120 has 0.035 cu ft/psi (120 cu. f.t @ 3442 psi), then a person with an SAC of 25 on an AL 80 has an RMV of 0.65 while a person with an SAC of 25 on a HP 120 has an RMV of 0.875. That is exactly what Stuart said - why don't you get that?

I think most of us understood that, if the same person dived an AL 80 and an HP 120 under the same conditions, their measured SAC would be lower on the HP 120 than on the Al 80 (but their RMV would be that same) - but that was not the example Stuart used.

 

[C Dub]

Clearly you have not spent much time reading posts by members of the Authoritarian Divers Party (a secret society who fears technology, change or individualism in the scuba diving world and travels under various three-letter acronyms whose names (acronyms) I will not mention. They pray at the alter of Halcyon (a long dead right wing dive god) and worship all things Hogarthian (an ancient cult into weird forms of bondage using nylon webbing). Ultimately, these folks subscribe to the principle that "You must dive the vay vee do and you vill only use dive gear vee approve of...or you vill die!" They can at times be held at bay by holding up a PADI dive traininig book and chanting "air integration is God's will!" It is rumored that wrapping one of them in a poodle jacket BCD will cause them to do whatever you say and answer any questions put them. Unfortunately, doing this banned by various international treaties on enhanced interrogation.

I have put my life at risk by even revealing their existence, but if I can save you from imminent death by Perdix by doing so, then I must...

Long Live the Resistance!

I love the spirit and humor of this post. Just wanted to point out that I have not seen a single GUE trained technical diver posting in this thread about AI on either side of the discussion.

 

[guyharrisonphoto]

Nailed it on algorithms, Stuart, at least for recreational dives. I have posted a lot about this. When researching computers I discovered there is NO evidence that one modern algorithm is "safer" than another in terms of reduced incidence of DCS for no-deco recreational diving. If you look at the manufacturers, you will see that they all call their algorithm something that suggests a "custom" alteration to the base algorithm. I believe that they add a conservatism factor to their program. So, you are not really diving pure "PADI (or Navy) tables" with DSAT, nor are you diving "pure" Buhlman with Scubapro or Pelagiz Z+. Since they are all equally "safe" statistically, I do not add any additional conservatism adjustment to my Scubapro Galileo (nor would I add it with any other computer) because that would unnecessarily cut my dive times and for no demonstrable benefit.

Now, with the Perdix, I wonder if you set it at 100/100 if that would give you the same NDL as pure unaltered Buhlman tables calculated from running computer software. If so, would that give longer NDLs than the proprietary algorithms of other manufacturers? If so, then adding GF will increase the conservatism, but it would be interesting to know what GFs would give similar NDL to the unaltered Suunto, Scubapro, Oceanic/AUP, Mares, etc, algorithms especially over repetitive dives.

Maybe, if you get the computer, you can use the dive planner to compare the Perdix and AUP algorithms for the same dive.

 

[guyharrisonphoto]

I love the spirit and humor of this post. Just wanted to point out that I have not seen a single GUE trained technical diver posting in this thread about AI on either side of the discussion.

I dive with a group of GUE divers (nicest people you would ever want to meet). They do not use AI but have no problem with my using it. I might be wrong but I don't think GUE would object to AI for recreational dives so long as the SPG was also in place on left waist D-ring. I do this.

 

[Lorenzoid]

1. I am only sometimes a solo diver. That designation just appeared when I joined the solo diver group. I often dive with a buddy or a small group and not infrequently, I dive with people I just met.

I see. No offense intended. Likewise, the "DIR" designation on mine just appeared when I joined that group, even before I ever took Fundies. It's pretty well accepted that the term is archaic. It also seems to carry some sort of negative connotation. I may have to become a Scubaboard Supporter to get rid of it!

2. Lighten up. Some "tech" folks take themselves way to seriously in my opinion and can be dismissive of others who do not dive the same way or enjoy the same aspects of diving. Sometimes I find that attitude amusing and will, from time to time, poke a little fun at it.

I get it. Yes, it was humorous.

I'm not a tech diver. I took Fundies only to learn how to make my diving safer and more enjoyable. I suspect there are far more of us GUE types who do NOT take ourselves way too seriously and are NOT dismissive of others than those who are. I read your post as poking fun at all of us. Please don't lump us all together. I agree there are SOME who are like that and so deserve a good ribbing, but it's because of what kind of person they are, not because of anything inherent in their training.