Do you still use a SPG with a AI computer?

[Flycaster]

Assumption 1: During most of the dive I have a camera in my right hand.
Assumption 2: With my vision I like to move the computer closer for reading.
Assumption 3: Use right hand for anchor lines ascending and descending.
Assumption 4: Right shoulder is better than the left so in bouncy seas prefer to hold on to the hang bar with the right.
Assumption 5: Use the pull dumb for releasing air so left wrist is always nearby.

Logical Conclusion: Put both computers on the left wrist.

It's all logical but I don't think im wearing two computers.

 

[BillyBayou]

I had been diving with only the console computer which shows air pressure (not wireless) and a wrist computer (no AI) and no SPG. I was doing a blackwater dive in a strong current. Began dive with 3400 psi. A few minutes into my dive I checked air and was at 1900. I thought that was odd. I stopped breathing for a second to listen for air escaping from my 1st and couldn't hear anything but again, 4" viz and strong current. I looked back at my computer and the pressure was flashing at 500. I was in 15' of water and immediately ascended.
After checking my gear on the boat, there was actually about 2000 psi in my tank. When I got home, I tore my system apart and found that the hose connection to the console computer was loose (never saw any bubbles coming from it).

I now replaced the console with an SPG and added a wrist computer with AI and still use my non AI as a backup. I'm very comfortable with this set up.

my .02

 

[stuartv]

There's a clear warning signal icon saying:

"Always use a backup analog submersible pressure gauge as a redundant source of gas pressure information."

It means they have conduct their tests to determine that their equipment isn't safe enough to be used alone. Even without having their data, you can understand yourself that a computer (that could contains software bugs) + a electronic probe + a wireless transmitter is inherently less reliable that a physical instrument, other wise you wouldn't have the above warning.
On the other side, did you ever see the spg instructions asking you to use a computer with AI for redundancy?

It's not a Warning. It's a Caution.

The Perdix manual also has a Caution that says:

"DO NOT RELY ON THE AUTO-ON FEATURE"

Does that mean that they conducted tests and determined that the Perdix Auto-on is not reliable, too?

 

[Flycaster]

It's not a Warning. It's a Caution.

The Perdix manual also has a Caution that says:

"DO NOT RELY ON THE AUTO-ON FEATURE"

Does that mean that they conducted tests and determined that the Perdix Auto-on is not reliable, too?

It's all "lawyer speak" from our history of junk lawsuits and our entire enterprise system at the mercy of lawyers and political correctness.

 

[stuartv]

It's all "lawyer speak" from our history of junk lawsuits and our entire enterprise system at the mercy of lawyers and political correctness.

I know that. It seems like @npole has a different idea.

 

[Marktan]

I dive the Hollis TX-1 computer (on my right wrist) using two wireless AI transmitters for my two side mount tanks (or one if back mount). I've got the redundant SPGs lollipopped on 6" hoses and bungeed to the 1st stage so they are there at a glance if needed, but I almost exclusively use the pressure(s) shown on my dive computer. I've never had an issue with transmitter dropping signal for any significant amount of time either in side mount or back mount using both steel and aluminum tanks (no more than 2-3 seconds - and usually when I'm swapping to the other tank and switching the selected transmitter).

They only problem I have ever had was last year while on a drift-dive in Mexico. Single back mount (so I couldn't see the SPG since it was on the 1st stage behind my head), the TX-1 computer was fine on the boat for the pre-dive checks, but randomly decided to shut down and gave me a blank screen with "altitude error" displaying for no apparent reason at depth (relatively shallow ~40-50') about 25 minutes into the dive. Up until that moment, however, I knew exactly how much air I had, as well as dive time remaining, and NDL time remaining (Thanks AI), so while I was really annoyed, I didn't freak out. Signaled to my wife (buddy) and the DM/guide that my computer died. Wife came over (familiar with my setup) and gave me the pressure remaining (plenty, no worries). I was getting ready to call the dive and deploy my SMB to start the ascent, but our DM/Guide came over, took a look at my SPG as well, and indicated for us to stay together and continue with the group (but above them). Figured she wouldn't do that without good reason, so we continued for about 15 more minutes (with my wife checking my SPG every so often) and surfaced with the rest of the group. Once on the surface, the DM said that she didn't want us separated so they wouldn't have to go look for us later. Sorta made sense I suppose, despite being against all the "don't dive without a computer" training I had pounded into my head up to that point. LOL.
I had them look at the and replace the computer's battery when we returned to the shop, and it fired right back up; haven't had an issue since. Strange.

 

[Kharon]

I finally took the hose & SPG off my reg halfway through my Bonaire trip. Over the last ton of dives I haven't looked at it once and the hose kept coming loose from the holder I had. Justy didn't want to deal with it anymore. If the AI craps out I'll just abort. I'll still have the hose/SPG in my save a dive kit if I ever need it.

 

[Diving Dubai]

Yes see the following in order of importance.

1. I can't be bothered to hunt out the HP port plugs that reside in a very safe and secure but mysterious location

2. I'm too tight to by new plugs, and can't be bothered taking off the SPG anyway.

3. Always use the SPG to check my gas when changing tanks, PDC is normally in a safe place. I'll align the two when I kit up

4. I always test breath using the SPG because that's the way I've always done it, and because the SPG has a better reaction than the AI.

 

[stuartv]

@Diving Dubai Come off a few bucks and buy a decent button gauge to replace the SPG. Then you don't have to find or buy HP port plugs and you can verify that your tank is more or less full without using your PDC. I mean, I realize you would have to open your wallet just a little, but...

As for #4: Why not just make sure your tank valve is all the way open by actually checking it? Then you don't need to look at your SPG when you pre-breathe. Also, with the number of DMs that mess with your tank valve just before you splash, it seems to me that the best habit would be to make sure you can reach your tank valve and then always check it to make sure it's all the way open right after you get in the water.

I got pretty feisty with a DM once just before I jumped off a boat with my doubles. Well, first I asked him politely to please not touch my valves. Then as I stepped to the exit, I saw him reach for them anyway. After it was all over, I realized that I was not going to get the DMs of the world to stop doing that. Particularly when it's a case like that particular one where the boat captain specifically instructs them to do it and he told me he was not going to change his procedures or make an exception for me. So, the best plan for me is to not be a PITA for the boat crew and just make sure I can reach my valves and then check it (or them) as soon as I hit the water. Nobody else is likely to touch them after that!

 

[Diving Dubai]

@stuartv

Yeah yeah, I know you're pulling my leg, but I don't need a button gauge. You see when we "big boy dive" we record our cylinder size and gas pressure (standard BSAC)

Point 4 Really - you want to go there Of course I check my tank valve, but that doesn't negate me from doing an idiot check before I splash.
Obviously you're at that complacent stage in you diving career where you're too cool not to need to
Seriously though. As A dive Pro, no one cars about you. No one buddy checks you and expects you to be infallible. Where're not. We get distracted dealing with customer whom we'd rather deep six. So I'm extra vigilant because I know I can make mistakes.

That said, rather than reach for the valve if I were to be that stupid (don't discount it) I would roll my gear off, sort the issue or ditch it and come back up. But then I didn't pass DM & IDC by doing gear on and off on my knees

I always check my clients gas. I work on the lowest common denominator. As an engineer (like you) I instinctively know which way is on and off. No righty tightly BS for me to remember.

As for "tech" divers... Well I have two parts to my boat briefs. The first for all - where I tell them that they've paid their money and we've banked it, so I'm not obligated to bring them back (light hearted joke)

Part two for tech divers. "You're all big boys and girls, if you choose not to carry out buddy checks etc, be sure I'll have your equipment on Ebay before your body is cold."