Shearwater Perdix AI wish list

[GreyVR]

GF99 is way, way too advanced for me. I tried to read a bit about it, and just got lost. I'm sure I'll get it soon.

I don't totally understand the utility of @+5 as opposed to TTS, but I think it's suppose to let you know if you are going to create additional decompression obligations?

But yes, this is all very helpful. I've got a much better idea how this puzzle is fitting together.

A couple of questions.... PPO2 is PURELY related to depth and not the clock? (99% sure this is correct,) and CNS is the um.... oxygen loading taking into account both pressure and time.... right?

Oh.... and for the record, my instructor sounds more like you, we just ran out of time on the last dive trip. It's padi's BOOK that has me spooked. It says things like "Exceeding 1.6 has the potential for IMMEDIATE ONSET OF OXY TOXICITY" and "OXY TOXICITY CAN COME ON WITH NO WARNING OR SYMPTOMS" ... So answer me this... If you messed up, maybe, got distracted, looked at your computer and saw say, 1.62ppo2, or 1.65ppo2, how worried would you be? What about 1.7?

 

[tbone1004]

@GreyVR GF99 and @+5 won't matter until you get into decompression.

ppO2 is a function of ambient pressure and fraction of O2, and is simply ppOs=ambient pressure*fO2 where ambient pressure is always atmospheres absolute instead of atmospheres gauge. I.e. 99fsw is 3atm, but 4ata so at 99fsw, air has a ppO2 of .21*4=.84

CNS clock is a weird one to explain. Basically you can inspire so many "units" of oxygen, but these units are exponential not linear, and I don't know what that exponent is off the top of my head. What is important to note with this clock is the general concept that your body is more susceptible to succumb to oxygen toxicity at high partial pressures, especially when working. That is why we try to limit ppO2's during the "working" portion of the dive to no more than 1.4, preferably down closer to 1.2, and we allow a partial pressure of 1.6 during decompression when you are resting.
Of important note while you are being spooked by the CNS clock, be aware than the CNS clock goes over by several hundred percent during a standard recompression procedure. If you are going to be spooked by oxygen, which you should be, it is high ppO2's, not the CNS clock that you should spook you.

The PADI book is emphasizing that last sentence. Many people have died almost instantly by switching to the wrong gas mix at depth. Particularly Oxygen instead of 50% at 70ft. That is a sudden spike to 3.2. I can tell you that as recently as 3 weeks ago I accidentally spiked my ppO2 on my rebreather to 1.8 for a couple breaths with no issues *don't advocate doing that obviously, was my error*. I will on occasion drop my O2 bottle at 25ft and start breathing it a few feet early *do not advocate doing that either btw* which is a ppO2 of 1.75. Those are things that can get you in trouble if you aren't careful. With normal nitrox mixes on open circuit though, you are limited to EAN40. If you set your computer to go off at 1.4, then you'll get flashing warnings starting at 82ft. You have up until 100ft before you hit 1.6, and have another 7ft before you hit 1.7. That's a 25ft window between 1.4 and 1.7 for you to get your act sorted out. That range widens with lower nitrox mixes so it isn't anything that should come as a surrpise. Default the Shearwaters start flashing and force you to confirm at a ppO2 of 1.65. If you want to lower that as a safety buffer, then go for it! I have to leave mine at 1.65 because it will get real mad at me during decompression, but if I was diving without O2 decompression, then I'd have no problem lowering that to 1.4

 

[admikar]

My wish would pertain to all SW models:while planing a deco dive with multiple gases, it would be nice to have two plans displayed:
1. "normal" dive plan,as displayed so far;
2. "lost gas" dive plan.
So you enter your parameters, dive plan is on screen, you switch screens until dive time/CNS is displayed. In my idea, after this point you keep going and get second plan displayed until you get to "new" dive time/CNS etc. After that you exit dive planner as usual.
I know this might get complicated with multiple deco gasses, but just an idea to munch on.

 

[tbone1004]

@admikar I think that's something that'd be nice for the desktop/phone app vs. the computer itself. Much easier to do on those where you can type parameters in vs. having to scroll through everything

 

[hammet]

I think a quickie way to define and select a FO2.
Defining the gases and then having to choose them in Select gas is too many steps and not necessary in Rec mode. In fact it's the only real configuration I will really ever do.

 

[admikar]

@admikar I think that's something that'd be nice for the desktop/phone app vs. the computer itself. Much easier to do on those where you can type parameters in vs. having to scroll through everything

I agree that would be easier on other platforms.
Example: we went on a two tank trip, did plan on Subsurface for both dives/both scenarios, then verified with computer itself (type in one dive/scenario, verify, repeat).
Did first dive, then had to change plans due to weather. Run planning on computer to check that I have enough gas. Again, type in parameters for first scenario, verify, change gases, verify new scenario. It would be easier if computer would run both plans by itself.
Again, I know it would become complicated with more than one deco gas, and it is not that important, but this is wish list thread.

 

[stuartv]

Side note, I wish it would run the calculation for PSI SAC to CUFT SAC in the ipad app for me if I plug in cylinder size.

Ditch the Shearwater mobile and desktop apps and switch to the (free) Subsurface and Subsurface-mobile apps.

Subsurface

I know more advanced guys likely have all that stuff memorized. On my last dive trip I was a little task loaded since it was my first time in current and my first time bringing a camera, so I want a cheat sheet.

Not that I am super experienced, but I do think that your planned max depth is something that you work out before you get in the water, and it factors in the gas you're using and your choice(s) on MOD.

Having your planned max depth memorized is, in my opinion, pretty important. It's also not that hard. Really, for most diving, the max depth will be whatever the depth is to the bottom, below you, so it's exceeding your MOD is not often something you really have to worry about. The obvious, common exception being if you are doing a wall dive. For a wall dive, you could write down your planned max depth on a slate or piece of tape or whatever, but really, it should not be that hard for you to remember.

 

[Erik Forsberg]

I would be most grateful if we could have three (3) configurable fields in Nitrox mode as well and not just two(2).
It's super annoying to not be able to show mini compass and two tanks at the same time in rec mode

Edit for clarity: Two tanks, both with their own fields just as in tech mode. It irks me so much that the layout in tech mode is so much better than in rec mode.

 

[jborg]

You can do that now with the customizable mini displays, though the text gets quite small.

 

[Erik Forsberg]

You can do that now with the customizable mini displays, though the text gets quite small.

Exactly. I would like to have the same interface as in tech mode. Three configurable fields