Gas Pressure Indication Redundancy

[DevonDiver]

Once again "electronics" caused a problem. At the very least, if you use electronics for gas pressure, you should have an analog spg as a backup.

It's important to know that this is your opinion - and not quoted advice reflecting the opinions or recommendations of any scuba agency, body or manufacturer.

Personally, my opinion, is that SPG redundancy is utterly irrelevant. The diver knows their air-state and, most importantly, knows that they have adequate air to complete their dive PLUS a calculated reserve. Should (electronic) SPG failure occur, then they can confidently abort the dive and ascend, in full knowledge of having a more than sufficient gas supply for slow ascent, safety stop and to obtain positive buoyancy on the surface.

Sometimes dives get aborted. That's a fact of life. The risk of SPG failure... balancing the cost and hassle of redundant SPG against the potential frequency of such a failure (extremely rare) does not provide a compelling argument for the need for redundancy. In addition to that, I believe that instructors should be more pro-active in encouraging divers to abort dives, when things go wrong.

There is far to much self and peer imposed pressure on divers to remain underwater when they feel uneasy or experience a failure - and this, I believe is a contributing factor to many serious scuba incidents.

 

[Superlyte27]

I used to dive a fancy AI Computer with all the bells and whistles. Granted this was two years ago, so perhaps the technology is better now. (I know it's not, because I still sell current models using the same exact transmitters, but hey wth)

What I found in my experience with the type of diving that I do is that AI simply cost me more dives than was convenient. Sure, it worked great for weeks at a time, but then I'd go several dives where it would lose signal. It would only lose signal for a second or two every 20'ish minutes or whatever, but even that second or two would require an abortion of the cave dive. Driving 2 hours, and making a penetration in a cave only to get halfway in and suddenly turn around because the AI computer wasn't reliable was a major PITA.

Unfortunately, I had to give it up. For me, having my gas pressure blinking on a few dives per month was more of a pain than reaching down and grabbing an SPG.

But that's just me.

 

[Randy43068]

Me too.

I used to dive a fancy AI Computer with all the bells and whistles. Granted this was two years ago, so perhaps the technology is better now. (I know it's not, because I still sell current models using the same exact transmitters, but hey wth)

What I found in my experience with the type of diving that I do is that AI simply cost me more dives than was convenient. Sure, it worked great for weeks at a time, but then I'd go several dives where it would lose signal. It would only lose signal for a second or two every 20'ish minutes or whatever, but even that second or two would require an abortion of the cave dive. Driving 2 hours, and making a penetration in a cave only to get halfway in and suddenly turn around because the AI computer wasn't reliable was a major PITA.

Unfortunately, I had to give it up. For me, having my gas pressure blinking on a few dives per month was more of a pain than reaching down and grabbing an SPG.

But that's just me.

 

[Splitlip]

Computers fail. I've had 3 failures in about 12 years. Only one time was my diving affected. After the first failure I picked up a citizens aqualand watch I used as a backup depth gauge. the last 2 failures I continued the trips with tables.

Anyway, back to the op. I presently dive with a wireless AI, a wrist watch computer and a brass and glass spg on a hose just long enough to clip off to the lower left corner of my plate.
The spg and watch are not even noticeable but are there if I need them. For me to thumb a dive or lose a day, it would take a failure of at least two, if not all three gauges. That would be highly unlikely.

 

[fnfalman]

Computers fail. I've had 3 failures in about 12 years. Only one time was my diving affected. After the first failure I picked up a citizens aqualand watch I used as a backup depth gauge. the last 2 failures I continued the trips with tables.

Anyway, back to the op. I presently dive with a wireless AI, a wrist watch computer and a brass and glass spg on a hose just long enough to clip off to the lower left corner of my plate.
The spg and watch are not even noticeable but are there if I need them. For me to thumb a dive or lose a day, it would take a failure of at least two, if not all three gauges. That would be highly unlikely.

Computers fail. Digital bottom timers fail. Mechanical bottom timers fail. Mechanical SPGs fail. Mechanical watches fail. Electronic watches fail.

Everything that can fail have failed. So what do you have to depend on? Your brain and your training. Those two are the only things that you can depend on.

 

[cool_hardware52]

I've had two brass and class SPG's fail underwater, both flooded, neither leaked, both were "stuck"

I will point out that there is a way to get a "gross" idea of the pressure in the cylinder, the stiffness of the hose.

A full tank makes for a very stiff high pressure hose, and an empty tank results in a limp hose. With a little practice one can learn to estimate the pressure by bending the HP hose.

This of course is not a way to start a dive, but it is a handy skill, and when tasked loaded a way to get a quick and dirty idea of remaining gas.

Tobin

 

[doctormike]

That's obvious. What do you do if your primary light dies while in a cave.... You turn right? We carry 2 or 3 cutting tools, 2 or 3 lights but only one way of monitoring our gas.

Well, I'm not a cave diver, but I think that you are comparing apples and oranges. A cutting tool or a light can save your life, an SPG can't.

A light or a cutting tool can actually change the outcome of a dive in the way that a pressure gauge cannot. If your SPG quits, you just assume that you have no gas and do the best that you can to get to the surface ASAP (although I would not do an unsafe ascent if I knew that I had enough gas at a recent check just before the failure to do a normal rate ascent, and that there was no leak).

 

[crls]

I do agree with you!

Actually your SPG is a backup of your brain, you should know your gas consumption rate and in time you can accurately know how much gas you have.
You don't need to read all the time your SPG and do not need a backup.
You can have a SPG spare part, so if one is damaged you can replace it on a dive trip.

It's important to know that this is your opinion - and not quoted advice reflecting the opinions or recommendations of any scuba agency, body or manufacturer.

Personally, my opinion, is that SPG redundancy is utterly irrelevant. The diver knows their air-state and, most importantly, knows that they have adequate air to complete their dive PLUS a calculated reserve. Should (electronic) SPG failure occur, then they can confidently abort the dive and ascend, in full knowledge of having a more than sufficient gas supply for slow ascent, safety stop and to obtain positive buoyancy on the surface.

Sometimes dives get aborted. That's a fact of life. The risk of SPG failure... balancing the cost and hassle of redundant SPG against the potential frequency of such a failure (extremely rare) does not provide a compelling argument for the need for redundancy. In addition to that, I believe that instructors should be more pro-active in encouraging divers to abort dives, when things go wrong.

There is far to much self and peer imposed pressure on divers to remain underwater when they feel uneasy or experience a failure - and this, I believe is a contributing factor to many serious scuba incidents.

 

[JamesK]

Your SPG is a backup for your brain. You should know what your tank pressure is at by looking at your depth and bottom time. Plain and simple.

I am not a fan of transmitters, but on an recreational ocean dive, go for it if you like it.

SPG's can and will flood and fail. Electronics can and will fail. Either way, dive over.

---------- Post added ----------

I do agree with you!

Actually your SPG is a backup of your brain, you should know your gas consumption rate and in time you can accurately know how much gas you have.
You don't need to read all the time your SPG and do not need a backup.
You can have a SPG spare part, so if one is damaged you can replace it on a dive trip.

Wow. I had this screen sitting up for a a while before I actually replied and then I see your post. You're smart!

 

[idive2]

When a simpler system such as an analog spg has a much lower incidence of failure
and probably less of a need to back up why would you want to add electronics to that
important bit of information. In ten years I have had approximately three electronic
items shut down at depth. Incidence of analog spg failure in same ten years...ZERO.
Slight inaccuracys maybe on the analog spg but failure to give me my PSI has never
happened.