Shearwater Perdix AI

[dmaziuk]

I don't have to wait to synch/pair an analog SPG manometer, or experience the frustration any momentary transmitter signal interruption at an inopportune moment (what if it happened with @Diving Dubai above?), nor deal with batteries and another potential O-ring failure point flood of a battery port.

No, that is why you will choose one tank-pressure-measuring device over another. All perfectly good but has nothing to with your mathematical prowess. Still a non sequitur, bzzt, thank you for playing, better luck next time.

 

[stuartv]

nor deal with batteries and another potential O-ring failure point flood of a battery port.

My AI transmitter has 2 O-rings. One on the battery port and another in the HP port. The current battery in mine is the original. 2 years old now and hasn't needed to be changed yet.

My SPG has at least 3 O-rings plus the chance of the HP hose itself getting damaged.

It takes longer for me to reach past a deco bottle, unclip my SPG hold it up, read it, and re-clip it than it does for my computer to regain synch with the transmitter on the rare occasion that I look at it and it has lost synch with the transmitter.

 

[Kevrumbo]

No, that is why you will choose one tank-pressure-measuring device over another. All perfectly good but has nothing to with your mathematical prowess. Still a non sequitur, bzzt, thank you for playing, better luck next time.

And so why do some divers choose to install both?

 

[stuartv]

And so why do some divers choose to install both?

I reckon they haven't learned to fully trust the AI yet. Or they already had an SPG and they think SPGs are reliable enough to warrant having the redundancy in spite of the extra failure points.

I only have an AI transmitter on my rec reg set - no SPG. For rec diving, I think one SPG is perfectly adequate.

I have an SPG on my left post tech reg and an AI transmitter on my right post. I would be comfortable taking off the SPG, but I keep it so that if I ever have to shut down the right post I will still have a working SPG for the gas I am breathing. I also use it to cross check my AI every now and then, to confirm my AI and my SPG both are working correctly. 2 SPGs is one and one is none, right?

 

[JohnN]

And so why do some divers choose to install both?

For me, AI is a convenience. The additional cost of AI over a non-AI computer is not an issue for me. If the AI stops working for whatever reason, I still have the SPG and can continue the dive. I lose the computer (and the backup), I scrub the dive.

 

[rhwestfall]

why do some divers put an spg on each post when diving manifolded doubles?

 

[Joneill]

Yes, an SPG is a gimmick too. Agree on that, It's all about awareness, it's about instinctively guestimating how much gas you and your teammates have left without having to be warned by some instrument. It's a sense that can be developed by training and experience, not by trusting technical solutions to do it for you.

By the way, I have seen divers getting into trouble with AI because they ignored alarms. They did not have time read numbers on their computer because they were to occupied with other things too much to bother to read their computer (high taskload). So there it is: is AI a soultion? Not to me if you're not aware about your situation. Is AI a usefull addition to your instruments? Yes it can be, just like a SPG. But in the end it's just a tool not the solution to be safe as some claim it to be. It's about how much you're relying on your instruments or on your gut feeling. I know I can trust my gut feeling, but verify my feeling through my instruments.

Is this hard to learn? Not really, I did it within my first 150 dives. I used AI as training wheels for the first 40 or so dives, then switched to SPG. But I only used GTR and such for the first 15 dives because it was off all the time and giving me the scares by it's nonsense warnings. Learned quickly to do the maths myself and trust on them.

Honestly, I don't understand how any device that displays one's tank pressure (SPG or AI) could ever be viewed as a gimmick? Without such a device, how would you even know how much gas in in your cylinder at the start of the dive? I've gotten AL80's with as low as 2700 psi and as high as 3300 psi? So regardless of how you calculate gas time, you need to know what you are starting with, no? For those of us who are not diving every week, I think the SPG or AI pressure data is really important to have and monitor during a dive - at this stage in my diving, I don't trust or really have a gut feel on gas.

 

[Diving Dubai]

And so why do some divers choose to install both?

I can answer that from my perspective at least.

1. Too lazy to take them off.
2. I use my SPG's when setting up my gear to check the tank pressures. Rather than getting my computer out switching it on etc.
3. Force of habit, is that I look at my SPG when carrying out pre dive breaths

It's not a trust issue at all.

I can't get hung up over failure points either. Most of the time it's a non argument in the real world. If an O ring is going to pop, generally its when its exposed to a sudden pressure change (turning your gas on) Or it's been leaking for a while and the person hasn't noticed or has been too lazy to change it.

Similarly batteries just don't go flat. If people can't be bothered to do the most basic checks before they pack to go diving, then they deserve what they get

 

[scubadada]

When I buy my new computer (it will be the Perdix AI) I am buying it for a few reasons:
1) Knowing pressures at a glance. Yes I have a fair idea of where it is going to be with a bit of experience.
2) Puts gas information in the same place as the rest of my information such as heading, depth.
3) AI allows me to look at my SAC in real time both while in the water and on the surface. I can see at a glance what a change in behaviour (kicking harder in an unexpected current, staying a few minutes longer at a depth) does to my dive time. That allows me to be better prepared the next time.
4) If I am diving an unfamiliar dive site, using new gear etc then my SAC might be way off what is "normal".
5) At this point in my diving I have only a general handle on what my SAC actually is as it covers a wide range due to the wide range of dive types that I have done to date. Which do I rely upon to work out the real SAC? The course dives (stressed due to it being a course), shore dive, the shore dive where the current changed halfway through, the shore dive where we had a lost buddy situation, the night dive on a reef, the night drift dive, the wreck dive, the wreck dive in surge, the night wreck dive. I don't have a bank of standard dives to work out what my SAC actually is because virtually all my dives were under different conditions and there is no "standard" set to work from.
6) The standard "take my gas at 5 mins and work out what I should have" works ok on square profile dives but on a typical shore dive here we might start at 6m, work out to 15-20 following the slope (which isn't necessarily at a fixed angle), travel at that depth for a while, then come back up along the slope and finish the dive with a shallow leg (which includes the "stop"). Not that easy to work out "on the fly" gas. I might have a general idea as to what I might use but accurate? No chance as there might be different currents on each leg.

@Kevrumbo - are you aware of anyone ever getting into trouble underwater from having more information such as that provided by AI?

I don't think, and I would be very surprised, if the Perdix AI calculates real time SAC (or, more importantly, RMV).

 

[stuartv]

I don't think, and I would be very surprised, if the Perdix AI calculates real time SAC (or, more importantly, RMV).

Actually, it does calculate and display SAC (if you set it to display it). That is, surface psi/min. It does not do RMV, as that would require configuring the computer with tank size.