Shearwater Perdix Air Integrated...Opinions

[Neilwood]

You both have missed the point. At least for me and I bet others it is not about calculating the gas consumption. I can do all that math in my head - forwards and backwards. It is about recording the base line data required for the calculation, the starting and ending pressure.

I go out for a day of diving and take a bunch of cylinders. They are all "full" and at the end of the day they are all "empty". After three dives I will be damned if I will recall the full or empty pressures. Yeah, I could take a slate or paper and write that crap down. But sometimes I do not have a slate or sometimes that piece of paper gets soaked. So the AI is nothing more than a data recorder, albeit expensive. But who cares it lets me be lazy, damn lazy, real lazy while blowing bubbles.

You know what they say about assumptions ... I have getting wet for over 30 years. While I know my typical gas consumption, I find and think there is value in seeing gas consumption over multiple dives as it can be of value for planning different dive types.

At the end of the day AI is going to be a point which folks are going to (hopefully) agree to disagree.

For a relative beginner like me it is probably even more important to see not only the overall rate I use gas but also the effect that specific things during my dive do to it (ie if I drop 5m to check a turtle out how does that affect my dive time?). Having specific data from during the dive I can work out exactly what is "costing" me dive time.

I can do the mental arithmetic in my head as well on the fly:
1) start with 230 bar, min return 50 =180 bar usable gas
2) Swim for 15 mins and use 60 bar means I should be planning on 45 mins total dive time assuming the same depth/conditions.

With the AI though I can see instantly how it is affected by a current etc.

 

[Kevrumbo]

You both have missed the point. At least for me and I bet others it is not about calculating the gas consumption. I can do all that math in my head - forwards and backwards. It is about recording the base line data required for the calculation, the starting and ending pressure.

I go out for a day of diving and take a bunch of cylinders. They are all "full" and at the end of the day they are all "empty". After three dives I will be damned if I will recall the full or empty pressures. Yeah, I could take a slate or paper and write that crap down. But sometimes I do not have a slate or sometimes that piece of paper gets soaked. So the AI is nothing more than a data recorder, albeit expensive. But who cares it lets me be lazy, damn lazy, real lazy while blowing bubbles.

You know what they say about assumptions ... I have getting wet for over 30 years. While I know my typical gas consumption, I find and think there is value in seeing gas consumption over multiple dives as it can be of value for planning different dive types.

At the end of the day AI is going to be a point which folks are going to (hopefully) agree to disagree.

You misunderstand. . .

The point is you already know what your nominal consumption rate at depth is for a given starting initial pressure, and your task is to reliably track your remaining cylinder pressure over time until some arbitrary low critical value like Minimum Gas Reserve/Rock Bottom, or Modified Third's Turn Pressure.

Again for example, a Tech dive at 60 meters/200'' with a bottom time of 35 minutes:

I have a full 200bar AL80 stage tank and I know my nominal consumption is 60 bar in five minutes at 60 meters depth; therefore after five minutes I know I have 140bar remaining (200 - 60 = 140):

So five minutes elapsed time and my SPG should read 140bar -check the SPG! It does.

Another five minutes for total ten minutes elapsed time and my SPG should read 80bar -check! It does.

Fifteen minutes elapsed time and my SPG should read 20bar -check! It does, and then switch to my backmount double AL80's which my consumption rate is 60 bar in 10 minutes at 60 meters. And do the same iterative subtraction to track & check remaining gas pressure all the way to the Rock Bottom value of 80bar: Starting with 200bar in the double AL80's, in ten minutes I will consume 60 bar with a remaining cylinders pressure of 140bar; and finally after ten minutes more for total elapsed bottom time of 35 minutes, I'm at Rock Bottom of 80bar and start the nominal ascent with my buddy to our deco stops & deco gas switches.

You don't need an digital AI/GTR function with wireless transmitters to perform this simple arithmetic above -->just reliable, mechanical no-battery-needed analog SPG's to confirm what you already know & figured about your remaining gas pressure. And more important -->You definitely don't want a WAI transmitter on your doubles that will time-out, lose sync, not recover and not register a reading due to "inactivity" because you started the dive breathing a separate stage cylinder as per the example above, especially at 60 meters depth!

 

[beester]

AI is like keyless entry or parking sensors in a new car. You hear about it, read about it, and decide you don't need it. But when you finally get to try these features, you'll never get a car without them.

I dive and teach Tec. I use AI in Tec (Doubles - AI on right post) and Rec (Singles). I still have an analog SPG in both config. The ease of just flicking your right wrist to check remaining gas is so convenient. Actually, there are more benefits in using AI in Tec with doubles.

The adoption of new technology is often presented in the form of a bell curve that breaks users into segments. You have the "innovators", "early adaptors", "late adaptors", and the "laggards". The only reason why the "laggards" buy touch tone phones is because they can't buy rotary phones anymore.

In the context of dive technology, Computers and Air Integration are new innovations that have proven themselves to be highly useful and reliable. Can you dive without them? Yes. Will they make your dives easier, more accurate, safer, and more enjoyable? Yes. When I'm penetrating a long and narrow passage in a wreck, I'm thankful that my computer has AI. With the flick of the wrist, I have all the vitals I need with minimal movements.

Across all industries, innovation is happening. We can choose to be innovators, early adaptors, late adaptors or laggards within the bell curve of change. Our mindset and personalities will make that determination. There is no right or wrong choice. Only what works for you.

Using your analogy (for tech divers, not talking for recreational): It's like having parking sensors but only fitted to the front of your car, but not on the back/sides. No use having the sensor if I still need old Mark I Eyeball to measure distances to side and back before parking.

When I'm penetrating a narrow corridor I don't need to look at a computer screen or my manometer to know what my usage is, I know! Just by simply taking my surface sac in BAR for my tank volume and multiplying it by the ATA. 50m wreck diving my normal double 12l set it's 20-24 bar per 5 minutes. (what Kev tried to explain). That's me looking to the front of my car when parking (ie your AI sensor).

But I still need to make the calculation and then visual check on manometer for my bottom stage and deco stages. That's me having to look over the back and sides of the car, because there are no parking sensors.

 

[lowviz]

...//... if I could dive safely with no instruments or calculations at all, I would. ...

That, truly, is the ultimate goal.

...//... I think it's great that Shearwater can now satisfy the data nerds, too.

One of the biggest data nerds on SB is Kevrumbo and they are doing nothing for him. Not everyone wants (or is able to) maintain that mental burden while enjoying a dive. I'm into post-analysis. Problem is, I find post-analysis highly lacking when using only an SPG and my usual running average SAC of 0.67. So I've come to love the electronic support with crap that annoys me. When to start up, how long to hang, yadda, yadda... Kevrumbo has no need for it. Fine, I understand and remain impressed with his approach. Not for me, though. I dive to see stuff and get lost in the other world. I also value my health. Thus the fascination with data.

Please consider this: Is is possible (for some people) that the more they offload the nuts and bolts of getting home safely, the more they can enjoy their dive?

 

[Scared Silly]

You misunderstand. . .

We are taking apples and oranges. Reread my post. I am discussing post dive needs. You are discussing calculations required during the dive. Apples and oranges.

Further, all I am stating is that I like the ability for AI to record my starting and ending pressure as well as current pressure. No where, am I using AI for any type of calculation during the dive. In fact, I noted the GTR calculation is not reliable. So not only is your post apples to oranges, it is moot.

Kevrumbo, we get it that you have zero need for AI. Great, happy diving.

 

[admikar]

You can easily work out gas consumption without an AI computer. All you need to do is download your dive data to a suitable software (Subsurface is perfect) and enter your starting and ending pressures and the size of the tank. Simple. So simple, I have been doing this with Subsurface and other software for 10 years.

I do not have a great number of dives, but this is what I have been doing. So far, I got my average SAC, add few liters for fudge factor and plan on that. Make a plan, check from time to time on SPG, and work from there. I do not need AI for that. I do not mind if someone do, but also, I need "that someone" to not mind if I do not need AI.

 

[clownfishsydney]

You really don't even need the software. . . Once again, how hard is it rounding to and working with multiples of 1 bar/min or even 2 bar/min pressure Sac rate??

Your whole post simply confirms it is not simple doing it that way. The correct answer is litres per minute, not bar per minute. Litres per minute works no matter the size of your tank, you are then comparing apples to apples. If you do it your way, you need to know the size of the tank and the multiplier effect needed to compare to someone else. Too hard.

 

[Kevrumbo]

Shearwater Perdix Air Integrated...Opinions

Your whole post simply confirms it is not simple doing it that way. The correct answer is litres per minute, not bar per minute. Litres per minute works no matter the size of your tank, you are then comparing apples to apples. If you do it your way, you need to know the size of the tank and the multiplier effect needed to compare to someone else. Too hard.

Read and comprehend the post again in the link above Mate . . . it's covered all in there. Your SPG reads in pressure units -NOT volume units- so it makes sense to use a working figure in bar/minute per ATA units.

So if I have a volume Sac rate of 22 liters/min and I use a 11 liter/bar AL80 cylinder, 22-divided-by-11 equals 2bar/min per ATA pressure Sac rate.

Savvy?

 

[Michael Guerrero]

Are you going to forego your traditional spg? If not, why introduce an additional failure point?

 

[lowviz]

Fair question.

Me? Lose the analog input for that information? No chance, my brain is analog. I'd still like to have the fuzzy notion of "how I'm doing" as my dive progresses. Throughout the body of the dive, I would most certainly glance at my SPG just to sorta kinda check how I'm approaching my usual "waypoints" without any form of conscious calculation. In times of need, or if I decide to linger, then I most certainly would be looking at my wrist. So it would add value during the dive along with a great value (to me) post-dive.

The added failure point is, statistically speaking, nothing.