Shearwater Perdix AI

[scubadada]

I mine not criticising you on your purchase. but I have to laugh. I took a ton of abuse because I chose the Eon Steel with it's high costs. Now I see that SW with their AI have a higher price point yet people see this is acceptable.

A really good example of how much extra a good brand can command in price

Perhaps it's because it has a widely available and used decompression algorithm rather than a proprietary, RGBM algorithm?

 

[undrwater]

Perhaps it's because it has a widely available and used decompression algorithm rather than a proprietary, RGBM algorithm?

This, absolutely.

 

[Basking Ridge Diver]

@stuartv - I understand your point.

But it is like every other electronic gadget out there. Folks don't want 2 or 3 or 4 versions ago - they want the latest if they can get it of course at the right price.

Losing $150 or $250 over 3 years is not bad if I continue to dive at the rate I am going - a little less than a dollar a dive. it is all relative and I actually needed a PDC with a decompression algorithm that I trusted but was waiting to see what was out there. Then my wonderful wife said go for it - the rest is history...

 

[dmaziuk]

I get AI/GTR for rec divers. But why on earth would a tech diver on a tech dive want GTR? I can understand AI to some extent even for tech, but GTR with even multiple tanks/gasses? Just don't get it.

They wouldn't. Hopefully the interface can be configured to display something else in the place of ATR numbers. Aside from the screen real estate, there's a small CPU load for calculating it, meaning slightly higher battery drain and potentially less cycles available for other computations. Assuming the subroutine cannot be turned off via a config option. I'm sure there's no shortage of cycles. I wonder how long your dive would have to be for the battery life to make a difference, and how much difference it'd make. I expect it's moot because we're talking dive times that mean you're carrying a different shearwater in your rebreather and ATR doesn't apply.

 

[Kevrumbo]

. . . .Apparently, all that simple math stuff is hard enough that even people who claim to know it and do it well can still mess it up and get bent. And I don't mean mess it up once. I mean, mess it up, then their buddy messes it up, too, so as to not prevent the team from making a mistake at the first deco stop. Then both people mess it up again at the next deco stop. And again and again, until both members of the team get out bent. Two people times however many deco stops is a lot of opportunities to catch those "simple arithmetic" errors and prevent either person from getting bent. And yet, despite how simple the arithmetic is, it can still happen and people still make those multitude of mistakes and get bent. It seems that narcosis is a b*tch!

It's a fact that people get mentally impaired by narcosis. It's a fact that narcosis is not completely predictable. It's a fact that people can get narced at 100' or even shallower - even if they've never been narced before. It seems to be pretty well accepted now that once onset of narcosis has occurred it does not just magically go away completely on ascent - there is a level of impairment that lingers. Anyone that chooses to dive relying on math done in the water - and especially after they've been at depth - when they have an option to use a simple, reliable computer to do the "simple arithmetic" for them (or at least to sanity check their mental math) is making a choice that I would deem sufficiently unsafe that I would choose not to dive with them.*

Would you dive with someone in big double steel tanks, a thick wetsuit, and no redundant buoyancy? "My buddy and I won't BOTH screw up the mental math" seems like a lot more suspect of a statement than "my wing won't have a total failure". If you have sufficient distrust of a wing to use redundant buoyancy, why would you not have at least as much distrust of doing mental arithmetic after being at narcosis-inducing depths?

Insulting people who choose to use their computer for a purpose that computers are good at - namely doing simple arithmetic for you - as a way to provide a safety backstop for their diving (as well as a data logging tool) seems, well, to be polite, extremely juvenile.

* No, I'm not saying I won't dive with anyone that doesn't have AI. I'm saying that I wouldn't be likely to dive with someone who's only way of knowing they have enough air is by doing mental math during the dive.

You conflate the issue Stuart.

If you don't know your gas consumption & management dive plan, you run the risk of running low or even out of air. If you don't know your deco profile plan, you risk DCI. If you don't know about breathing a dense gas like Air at deep depth with physical exertion, you get CO2 retention Narcosis/Hypercapnia.

Wireless AI does not resolve and is not a cure for ignorance. . .

 

[stuartv]

You conflate the issue Stuart.

No, I'm not. Arithmetic while diving is arithmetic while diving. You constantly post harping on how people should be doing arithmetic while diving instead of letting a computer do it for them. It doesn't matter whether you're talking about arithmetic for working out gas requirements or arithmetic for an ascent plan. It's arithmetic while (possibly) narced. Making that part of your normal process, instead of using a process that obviates the need for that, seems patently less safe, whether it's part of your process for figuring gas requirements or for figuring an ascent.

As you say, one is for preventing drowning and the other is for preventing getting bent. Personally, I'd rather be bent than drowned, so i would say that preventing yourself from running out of gas is more important than stopping yourself from getting bent. So, even more reason to use a computer to help you (along with proper pre-dive planning). And note that, while drowning is worse than getting bent, the people you're trying to convince to do arithmetic during a dive to prevent drowning (rec divers) are very likely to be even less well-prepared for that than the people you would suggest to do arithmetic to prevent getting bent (tech divers). How much sense does that make??

Plan your dive (before you get in). Use a computer in the water to help you follow your plan and avoid mistakes. Doing it on the fly, in the water, in your head, when you have an easier, more reliable option, is macho bollocks.

Tech divers all over the world trust Shearwater computers every day to get them out of the water without getting bent. Deco computations are an inexact and very complicated science. And yet people trust Shearwater (and other computers) to do it and without second-guessing the computer's results in midwater. Gas Time Remaining computations are trivially simple, in comparison, when you're talking about only using a single gas supply. Why would you trust a SW computer to get you out of a 200' trimix dive with deco, without getting bent, and not have at least as much faith in it to get you out of the water without running out of gas at the end of a single tank dive??

 

[Kevrumbo]

No, I'm not. Arithmetic while diving is arithmetic while diving. You constantly post harping on how people should be doing arithmetic while diving instead of letting a computer do it for them. It doesn't matter whether you're talking about arithmetic for working out gas requirements or arithmetic for an ascent plan. It's arithmetic while (possibly) narced. Making that part of your normal process, instead of using a process that obviates the need for that, seems patently less safe, whether it's part of your process for figuring gas requirements or for figuring an ascent.

As you say, one is for preventing drowning and the other is for preventing getting bent. Personally, I'd rather be bent than drowned, so i would say that preventing yourself from running out of gas is more important than stopping yourself from getting bent. So, even more reason to use a computer to help you (along with proper pre-dive planning). And note that, while drowning is worse than getting bent, the people you're trying to convince to do arithmetic during a dive to prevent drowning (rec divers) are very likely to be even less well-prepared for that than the people you would suggest to do arithmetic to prevent getting bent (tech divers). How much sense does that make??

Plan your dive (before you get in). Use a computer in the water to help you follow your plan and avoid mistakes. Doing it on the fly, in the water, in your head, when you have an easier, more reliable option, is macho bollocks.

Tech divers all over the world trust Shearwater computers every day to get them out of the water without getting bent. Deco computations are an inexact and very complicated science. And yet people trust Shearwater (and other computers) to do it and without second-guessing the computer's results in midwater. Gas Time Remaining computations are trivially simple, in comparison, when you're talking about only using a single gas supply. Why would you trust a SW computer to get you out of a 200' trimix dive with deco, without getting bent, and not have at least as much faith in it to get you out of the water without running out of gas at the end of a single tank dive??

It takes longer to describe & explain the process below than to actually do it -which is why those without the patience & motivation to comprehend & learn, purchase the quick solution extravagance of wireless AI.

I have a full 200bar AL80 tank and consume 30 bar in five minutes at 18 meters depth; therefore after five minutes I know have 170bar remaining (200 - 30 = 170):

So five minutes elapsed time and my SPG should read 170bar -check the SPG! It does.

Another five minutes for total ten minutes elapsed time and my SPG should read 140bar -check! It does.

Fifteen minutes elapsed time and my SPG should read 110bar -check! It does.

Twenty minutes elapsed time and my SPG should read 80bar -check! It does, and then start a multi-level ascent to the shallows around 9 meters where I use 20 bar in five minutes. Finally ascend to complete a three minute safety stop, surface & inflate bcd, and I know my SPG will show 35 to 40bar remaining. . .

And so begs the question: do you really need the expense of wireless AI to tell you what you already know about your consumption rate (or should be motivated to learn & figure out in the first place), over the practical & economic utility of a basic bottom timer/dive computer and SPG? Is it really so hard to perform the subtraction arithmetic above -both on pre-dive planning & real-time during the dive- without an AI feature?

[Especially for all Metric System users with typical nominal pressure Sac rate values of one to two bar per minute, you don't need the Air Time Remaining functions of an AI feature: In other words, how difficult is it to do in your head multiples of 1 bar/min or even 2 bar/min??]

 

[dmaziuk]

how difficult is it to do in your head multiples of 1 bar/min or even 2 bar/min??

But you still check your SPG, don't you? If yes, then you're the one conflating the issue: one argument is hoseless vs hosed SPG, another one is guesstimated ATR vs actual tank pressure, and a different one still is mental arithmetics vs a measuring device. Or is your argument: do I really need the expense of an SPG when I already know what my gas consumption rate should be and am capable of performing kindergaden-level addition in my head.

 

[stuartv]

It takes longer to describe & explain the process below than to actually do it -which is why those without patience & motivation to comprehend & learn, purchase the quick solution extravagance of wireless AI.

And the point is that no matter how quick and easy it is, on land, it will always be harder when (possibly) narced and never as quick (or as low of a task load) as letting a computer do it for you.

For someone who is completely dependent on their computer to calculate their NDL (or their mandatory deco) for them, what argument can you make that that is okay, but letting it calculate GTR is not okay?

If you want to have people not rely on their computer for either thing, then we're back to having a mechanical depth gauge, a physical SPG, and a wind-up dive watch. If that's how you want to dive, that's fine. I certainly have no interest whatsoever in getting you to dive differently. But, dang! Recognize that the rest of the diving world has moved on and embraced newer technology. Technology that has proven itself to be more than adequately reliable and precise (and safe) over a period of years of use. Give it a rest on getting people to try and go back to old tech ways of doing things.

If the current, modern ways are not safe, please provide actual data, not a list of threads that you think support your position and would require reading hundreds of posts just to have a discussion about it. Can you provide ANY data to support an assertion that GTR calculations in a wireless AI computer system have resulted in any number of deaths? If people aren't dying (or getting hurt) from using it, what is the problem? Just that you don't think it's worth the money and you're pissed that other people are spending their money in a way that you wouldn't?? Crikey! The number of times I've seen people rant against other people buying something where the root of their argument really and ONLY boils down to the ranter doesn't think the item under discussion is worth the price! That is purely a budget decision, which is none of your business unless it is you that is debating making the purchase for yourself.

Or maybe you're pissed that other people don't have to learn to do the math like you did? Do you think people should have to learn how to change and gap a spark plug before they drive a car, too?

 

[luscioman]

It takes longer to describe & explain the process below than to actually do it -which is why those without the patience & motivation to comprehend & learn, purchase the quick solution extravagance of wireless AI.

I have a full 200bar AL80 tank and consume 30 bar in five minutes at 18 meters depth; therefore after five minutes I know have 170bar remaining (200 - 30 = 170):

So five minutes elapsed time and my SPG should read 170bar -check the SPG! It does.

Another five minutes for total ten minutes elapsed time and my SPG should read 140bar -check! It does.

Fifteen minutes elapsed time and my SPG should read 110bar -check! It does.

Twenty minutes elapsed time and my SPG should read 80bar -check! It does, and then start a multi-level ascent to the shallows around 9 meters where I use 20 bar in five minutes. Finally ascend to complete a three minute safety stop, surface & inflate bcd, and I know my SPG will show 35 to 40bar remaining. . .

And so begs the question: do you really need the expense of wireless AI to tell you what you already know about your consumption rate (or should be motivated to learn & figure out in the first place), over the practical & economic utility of a basic bottom timer/dive computer and SPG? Is it really so hard to perform the subtraction arithmetic above -both on pre-dive planning & real-time during the dive- without an AI feature?

[Especially for all Metric System users with typical nominal pressure Sac rate values of one to two bar per minute, you don't need the Air Time Remaining functions of an AI feature: In other words, how difficult is it to do in your head multiples of 1 bar/min or even 2 bar/min??]

So what you are saying is you are depending on a electronic device (watch or bottom timer) to tell you when it is 5 minutes and not 4 minutes or 6 minutes.