SPG or not

[Tracy]

As an old mossback, I consider both systems additional and points of likely failure. Gimme my Double Hose USD Mistral and a J valve, I'm set without using either of those non-zero likelihoods of failure.

I was just diving that very setup two weeks ago. Still works perfectly.

 

[NothingClever]

I'm currently training to be an Advanced Close Minded Luddite so no AI for me.

 

[Eric Sedletzky]

SPG's blowing out is a laugh
Just buy a good one and make sure the O-rings on the spool are HP rated. If they are duro 70 or less they can extrude.
If SPG's were that prone to failure you wouldn't see extreme technical or cave divers using them.

 

[Eric Sedletzky]

I'm currently training to be an Advanced Close Minded Luddite so no AI for me.

"Luddite Diver" don't tell Patty.
These philistines around here have no imagination.

 

[NothingClever]

Hey, this is serious stuff.

 

[Badger7]

If your SPG gave a you a drastically different reading than the AI, what would you do?

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.

AI fails in a safe manner

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.
Battery change and reset didn't resolve the issue, so Garmin replaced under warranty.

If you don't trust the air integration, then why use it? Stick to an SPG.

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.

My mask could break, my wetsuit, et cetera. I don't carry extras.

I do, spare mask in a pocket. I need to see and I need to breathe, pretty much everything else is comfort and convenience.

I'm not trying to change your mind, by all means you do you, just explaining why I do both in case anyone is at all interested.

 

[Centrals]

I use 2" spg for rec or tec dive and TWO simple dc(28yrs old).
User replaceable battery for the computer if I am in the market(highly unlikely) because I have two more dc as back up. BTW, no RGBM.

AI +spg? Personal choice, no right or wrong.

 

[jadairiii]

I was diving about 10 years when the first computers hit the market. I have had WAY more computers fail then SPGs.

On most recreational dives, if my computer fails, I still have a watch, I know the max depth of the water and I always carry a compass.....I'm still diving. And if my SPG fails, I get another for under $100, what's a new transmitter cost?

 

[34109411]

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’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 spg . no worries.

 

[LI-er]

i now use AI so i ditch the spg. Worst case scenario i abort the dive.I do carry a pony bottle with an spg . no worries.

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