SPG with AI computer?

[grantctobin]

Ridiculous.

I have witnessed a number of transmitter failures over the years, from outright crap-out; blown OPVs; early stage interferences from other divers -- as well as flash photography; and quite a few simply sheared off during rough handling by crew.

Of SPGs, I've only seen occasional leaks solved by a fifty cent spool or an HP hose failure upon pressurization; and even the manufacturers were quick to note their limitations:

You should get out more. I'll asterisk the above with "PPS + Swift transmitters that aren't abused."

 

[Boarderguy]

Keep the SPG in your SAD kit. It really is not needed on basic rec dives. IF, and that's a big IF, your computer/transmitter suffers a problem then you bail on that dive. Swap the SPG over during the SI and go diving on the next drop. I keep a PP2 in my SAD and the only brass & glass I have lives in my garage SAD kit.

 

[Brett Hatch]

At the very least, having a second SPG in your save-a-dive kit is a good idea. Whether you leave it on the reg is a personal choice. And like many personal choices, it's a contentious topic on SB, as you can see.

Personally, for my dives (with no deco ceiling, and no hard ceiling): a failed transmitter or failed computer are neither common, nor life-threatening problems. So I'd be perfectly happy diving with just the transmitter and leaving the SPG topside. But, I have not gotten around to removing my SPG, and it gives me the warm-fuzzies to compare the brass SPG to my computer every now and then. So I dive with both, but may remove the SPG some day.

I have no opinion on whether SPG failure rates are higher or AI transmitter rates are higher, they both seem to fail infrequently. I have never had an SPG failure, and have never had a transmitter failure. Never had a computer failure either, come to think of it.

 

[Subcooled]

Ridiculous.

I have witnessed a number of transmitter failures over the years, from outright crap-out; blown OPVs; early stage interferences from other divers -- as well as from even flash photography; and quite a few simply sheared off during rough handling by crew.

None of the commercial diving firms for which I worked, over the last twenty years would allow their use, without mechanical redundancy -- and I trust that particular practice of industry over the varying tastes of dilettantes and weekend warriors.

Of SPGs, I've only seen occasional leaks solved by a fifty cent spool or an HP hose failure upon pressurization; and even the transmitter and computer manufacturers were quick to note their limitations and encourage SPG use:

If a SPG hose fails, it gets noticed. It is the unnoticed errors that kill.
A SPG does not experience electronic failures nor communication issues. A Bourdon tube is quite reliable.
An analog gauge is easier to understand when narced (I do have experience of this from 50m on air).

 

[mcohen1021]

I still feel like I need to have my SPG with me as a back up. (It's just an Oceanic swiv, no console)

Am I overdoing it, or is the redundancy standard-operating-procedure?

Keep the SPG, a single pressure gauge. secure it along side of your power inflator and forget about it.

 

[Subcooled]

Keep the SPG in your SAD kit. It really is not needed on basic rec dives.

I would disagree.
The ONLY gauge you will ever need on a basic rec dive is the SPG.

Given that one cylinder of air and the very moderate max and avg depths, decompression illness is quite unlikely.
Some week long liveaboards are an exception.

 

[PaulVS]

So my initial thinking was along these lines.... feel free to correct anything I'm erroneous on....

It seems that the three thing that are "critical" to function for lack of a better word.... your regulator, some kind of pressure gauge, and your mask. I can ditch weights and manually operate a BC to some degree, and swim without fins.

I can't conceive of breaking or losing my mask, but I could ascend without it fairly decently if I had to I imagine, even with a safety stop. My regulator (at least the 2nd stage) has redundancy with my octo, and my buddy's octo if necessary. So that leaves the pressure gauge.... and a computer watch with AI seems to have a lot more potential failure points, even acknowledging the advancements in reliability. I guess I question whether I'd want to cut a $100 dive short because I didn't have an additional 10 ounces of backup.

Obviously I'm only talking about ~20-80ft "caribbean rec dives" and wireless AI relative to this issue.

 

[CuzzA]

Some do. Some don't. I don't wear an SPG. Do what makes you comfortable.


Pros and cons: AI alone means no extra failure point and one less hose to replace and it's more streamlined. If the TX fails it doesn't give a false reading like what can happen with a stuck SPG. AI is safer than an SPG. Both would be safer than either one alone. Back in the day they had neither.

 

[Boarderguy]

The ONLY gauge you will ever need on a basic rec dive is the SPG.

Incorrect sorta...
You need a depth Guage and bottom timer (computer?), you don't need an SPG. Plenty of dives with my J- valves and pulling the handle when it breathes hard. I now dive a perdix AI, 40" primary and a SP air 2 and a back mounted pony. No extras because they aren't needed.

For this dive trip if near the beginning it sucks, but go up or start a bit more shallow and use your average consumption to gage when to go up (obviously easy earlier than normal). Mid dive start going shallow and look at ending it soon if you don't know your recent pressure. End of the dive, just go up.

 

[MaxBottomtime]

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