SPG or not

[inquis]

When there’s a leak from the SPG it’s usually at the HP Spool O-rings … and it’s typically a tiny stream of bubbles that have no impact on gas usage for a NDL open water dive

No disagreement with "typical", but I've also seen that trickle escalate well beyond that. I'm not saying it's life threatening like an LP hose failure, but the dive still ends.

Also, your AI transmitter has the same vulnerability and greater vulnerabilities as an SPG, judging from the recalls.

Agree to disagree on that, but won't elaborate as it's irrelevant. AI is a given (i.e., yielding whatever benefits made you buy it in the first place), and the question is whether to add an SPG or not. I do hope you'd agree that the likelihood of a dive ending leak is higher after adding those additional failure points.

 

[scubadada]

No disagreement with "typical", but I've also seen that trickle escalate well beyond that. I'm not saying it's life threatening like an LP hose failure, but the dive still ends.


Agree to disagree on that, but won't elaborate as it's irrelevant. AI is a given (i.e., yielding whatever benefits made you buy it in the first place), and the question is whether to add an SPG or not. I do hope you'd agree that the likelihood of a dive ending leak is higher after adding those additional failure points.

I've dived a backup SPG to AI for 15 years. I've had a couple of mild leaks from the spool, nothing even close to dive ending. I have extra spools in my SAD kit.

 

[Umuntu]

Agree to disagree on that, but won't elaborate as it's irrelevant. AI is a given (i.e., yielding whatever benefits made you buy it in the first place), and the question is whether to add an SPG or not. I do hope you'd agree that the likelihood of a dive ending leak is higher after adding those additional failure points.

As with a lot of technology we reach a point of “peak trust” in the technology rather than in the analog tools which have gone before.

The failure points in the electronics in your transmitter, dive computer and the signal between them are far more numerous than the relatively simple pressure transmission, hose, 3 o-rings and bourdon tube that is your typical SPG system.

BTW, I also use 2 dive computers … in case one falls I have a backup so that I can continue diving on trips. And since I have experienced depth sensor failure on one of my dive computers, and a recall of my AI transmitter, I have a healthy scepticism about the reliability of AI dive computers.

 

[inquis]

The failure points in the electronics in your transmitter, dive computer and the signal between them are far more numerous than the relatively simple pressure transmission, hose, 3 o-rings and bourdon tube that is your typical SPG system.

Again, that's not relevant, as we're not discussing eliminating the AI chain. We're talking about adding another device with a non-zero likelihood of failure. The question is then whether that helps more than it hurts. I feel it's a net negative, but opinions will vary.

 

[Umuntu]

Again, that's not relevant, as we're not discussing eliminating the AI chain. We're talking about adding another device with a non-zero likelihood of failure. The question is then whether that helps more than it hurts. I feel it's a net negative, but opinions will vary.

Or subtracting. I see the addition as the AI “chain” … with the SPG system as being part of the standard set of system components.

It’s amusing how this debate has evolved over the last ten years … from whether we should trust AI to whether we should continue to use an SPG.

 

[USdiver1]

Again, that's not relevant, as we're not discussing eliminating the AI chain. We're talking about adding another device with a non-zero likelihood of failure. The question is then whether that helps more than it hurts. I feel it's a net negative, but opinions will vary.

I guess it depends on your perspective as to which system, AI or SPG, you would consider being the additional. Most divers trained pre-AI computer would consider the AI system the additional one, while those trained with Air Integrated computers would see the SPG analog system as the additional one. . . Interesting.

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.

 

[Eric Sedletzky]

You asked why not a console?
A lot of people don't like consoles because they are big and cumbersome, they can bang into stuff, and you have to unclip them or use a retractor to use the compass which means you also need a longer HP hose so you have room to do that. Retractors can lose their spring back tension and start pulling out when you don't want them too. Some say they are nothing but a huge entanglement hazard too.
You can use a small SPG clipped off to your left hip D-ring with a shorter HP hose. A lot of people feel better having an analog back up even if they have a sender, and it's out of the way.
Having the rest of the stuff on your wrists is very convenient and streamlined, nothing hangs down, it's right there to look at it. I have a compass on my left arm and my computer is on my right arm (sometimes on the left along side my compass if I'm working). If you have a computer with a built in compass then even better - two in one!, keep it on your left wrist.

 

[LI-er]

I do hope you'd agree that the likelihood of a dive ending leak is higher after adding those additional failure points.

That's just silly. The odds of a dive ending hose leak are so remote it will never happen to the vast majority of divers.

 

[LI-er]

As for replacing the hose, I rent so I don't have to worry about that.

Not all dive ops will let you swap out your transmitter on their rental first stages. But if and when you do, you don't need a wrench for the transmitter, hand tight is usually sufficient.

 

[CuzzA]

The failure points in the electronics in your transmitter, dive computer and the signal between them are far more numerous than the relatively simple pressure transmission, hose, 3 o-rings and bourdon tube that is your typical SPG system.

I've never heard of anyone running out of gas because of an AI computer.

I have heard people running out of gas because the needle got stuck on an SPG at some point and at the time they thought they could continue the dive when they should have been heading up.

AI fails in one way. It no longer gives you a pressure to make a decision.

My Teric and an Icon before that has momentarily not displayed the gas. I keep my eye on it and within seconds it pops back up. That is rare.

To each his own, but anecdotally I've got over 500 dives on AI alone and have never needed an SPG.