Hey, this is serious stuff.
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If diving a single tank and single first stage, and they both indicate a pressure but well out of sync, work off the assumption that one of them is wrong, knowing I cannot trust either. If diving doubles, conduct a valve flow check in case both AI and SPG are actually correct and the tanks aren't balancing out. In either case, assuming a quick equipment diagnosis is fruitless, as with any equipment failure, immediately abort the dive, working off the lower of the two values, and in a dual reg configuration, breathe off the reg connected to the first stage indicating higher pressure, keeping an eye on whether pressure is dropping at the expected rate during the ascent.If your SPG gave a you a drastically different reading than the AI, what would you do?
Last summer my Garmin T2 tranceiver stopped reporting at 110' on a wreck, midship. Dive plan was to swim through the hull and return to the ascent line on the far side to the stern. Backup analog SPG indicated more than enough gas in the tanks to remain at depth for a few more minutes, complete the turn as planned, and head back to the line and perform a normal slow ascent without going on anyone else's back gas. The only reason that was a safe failure was having an SPG reading as a backup, otherwise it would have been a matter of popping an SMB, aborting the dive early, and getting back to the boat via surface swim, which would have been less safe overall.AI fails in a safe manner
I don't trust blindly trust anything, and if I can easily and cheaply achieve some redundancy, I can't see a good reason not to. I do like having the AI gas information integrated into logging, and appreciate being able to review and compare gas usage. To me, that is well worth replacing a $30 HP hose every 5 years. Thats less than the bar tab I'd pick up if we were having this conversation in person over tacos and a beer.If you don't trust the air integration, then why use it? Stick to an SPG.
I do, spare mask in a pocket. I need to see and I need to breathe, pretty much everything else is comfort and convenience.My mask could break, my wetsuit, et cetera. I don't carry extras.
I’m not new to diving but I’m very new to dive computers and recently was suggested that in addition to my wrist mounted AI computer that I get a SPG too. Is this common and what’s the point? Why not a whole console?
i now use AI so i ditch the spg. Worst case scenario i abort the dive.I do carry a pony bottle with an spgI’m not new to diving but I’m very new to dive computers and recently was suggested that in addition to my wrist mounted AI computer that I get a SPG too. Is this common and what’s the point? Why not a whole console?
cause i only dive solo i should have specified. i am really careful for that matter. The idea to wait for a difficult breathing is not good for me.Why would you abort a perfectly dive after losing the ability to monitor the pressure in your main tank if you've got a full pony bottle?
You feel the breathing getting more difficult on the primary, then you switch to the pony and end your dive.
Easy peasy
... pull your J valve, and enjoy your trip to the surface with plenty of air.You feel the breathing getting more difficult on the primary, then you
Exactly. I’ve had an SPG fail before. It did exactly that. I only noticed as it was a type of dive I’ve done many times before, and had a pretty good grasp on what I should be seeing at that point. The SPG was telling me I had much more gas than I really had.When they do fail, they fail the wrong because they stick, indicating you have more gas than you do. AI fails in a safe manner.
If you don't trust the air integration, then why use it? Stick to an SPG.
I dive solo as well. If I lost my ability to read tank pressure (Unlikely as I dive a transmitter, 2 receivers and a mini analog spg), I'd have no issue with the safety aspects of switching to my pony when the breathing gets difficult. It's not a complicated maneuver, and if you can't trust your pony bottle as a backup then why bother carrying it in the first place?
you don't understand what i said. too complicated sorry english is not my first language.I dive solo as well. If I lost my ability to read tank pressure (Unlikely as I dive a transmitter, 2 receivers and a mini analog spg), I'd have no issue with the safety aspects of switching to my pony when the breathing gets difficult. It's not a complicated maneuver, and if you can't trust your pony bottle as a backup then why bother carrying it in the first place?