SPG with AI computer?

[Robert H. Diver]

I only use transmitters now, unless I’m taking a course where the instructor requires SPG’s.

 

[gmerick]

Will you use (be learning to use) the dive features of your AI computer?
Will you be diving profiles where additional redundancy is needed?
If the AI will just be to have the tank pressure in digital form on your wrist, the SPG is not needed. AI is more reliable and less prone to damage than SPG. On a "normal" day trip dive, if SPG or AI fails, abort the dive, do a safety stop and return to boat. Doesn't matter with SPG, AI, or both.
If surface conditions, overhead environment, deco commitment don't permit that, use both.
I do sidemount with AI, and SPG on both tanks. I've had two SPG failures, and an SPG hose leak. No AI failures.
I prefer to have the redundancy, but I've lost vacation time dealing with it.

 

[DirtFish]

For all you that say SPG's never fail I call Bullsh!t. In 30 years as a fire department USAR diver in conditions that that no human should dive in I have had 5 SPG failures. In leisure diving I have had 2 SPG failures, 1 just a week ago during a tech class in Curacao where it was required. Luckily we were sidemount so I could shut down that tank. I now always dive AI and after countless (1k+) dives on shearwater computers I have not had a single problem. You are lucky if a glass cover blows out, the plug blows or the fitting loosens and the entire gauge blows off, not so lucky if the needle sticks at 1000 psi.
These posts are like comparing rotary dial phones to cell phones. Come on people, this is 2023.

 

[MaxBottomtime]

I've had one spg stick in 34 years of diving. I've had intermittent transmitter failures on about 10% of my dives using an AI computer. It loses its signal for a few minutes at a time. It happened with two different transmitters and two different computers.

 

[Moerae]

Backup SPG is a totally trivial tradeoff. I have no idea why it causes so much debate.

You're decreasing the tiny chance of information loss in exchange for a tiny increased chance of gas loss.

Transmitters can fail, spgs can get stuck, but in either case the chance of a permanent loss of information is a non issue. You abort the dive and as long as you were following a sane gas plan and not ignoring your consumption, you know you have plenty to get back to the surface if you abort once you confirm it's not working and isn't a temporary issue.

You can mitigate that tiny chance of needing to abort the dive, due to information loss, by adding a backup spg. But then all you've done is added a tiny increase in chance of gas loss needing an aborted dive. HP hoses drain super slow, so that's not an emergency either (recreational it drains too slow to prevent a safe ascent, and in tech you would just isolate if it's a worst case total failure of the hose/orings).

So, in all cases, in all configurations, you're just trading off between tiny chances of minor issues that present almost no safety risk and just cause an aborted dive.

Just dive what you want.

 

[Altamira]

I think the question you have to answer for yourself and potential dive buddy is whether you are OK with thumbing a really good dive for yourself and buddy should your AI crap out? Personally, I would really be pissed at myself if I screwed myself and buddy out of completing the dive because I erroneously assumed my precious AI computer would not fail, and I was too lazy or overly confident to carry a backup SPG. I’m 77 and have never had any electronic device that has never failed. It is not a question of if, but when is the item going to fail?

 

[Belzelbub]

You are lucky if a glass cover blows out, the plug blows or the fitting loosens and the entire gauge blows off, not so lucky if the needle sticks at 1000 psi.

Exactly. Any piece of gear can fail. I'd consider both SPGs and most transmitters to be quite reliable, but that doesn't change the fact failures can happen. When a failure happens, it now becomes quite important that the failure is recognized. With a transmitter failure, it's likely going to be quite obvious. My experience with SPG failures is more limited, but I did not like the failure mode at all. It was not obvious that there was a problem.

I think the question you have to answer for yourself and potential dive buddy is whether you are OK with thumbing a really good dive for yourself and buddy should your AI crap out? Personally, I would really be pissed at myself if I screwed myself and buddy out of completing the dive because I erroneously assumed my precious AI computer would not fail, and I was too lazy or overly confident to carry a backup SPG.

I slightly reworded your message below.

"I think the question you have to answer for yourself and potential dive buddy is whether you are OK with thumbing a really good dive for yourself and buddy should your SPG crap out? Personally, I would really be pissed at myself if I screwed myself and buddy out of completing the dive because I erroneously assumed my precious SPG would not fail, and I was too lazy or overly confident to carry a backup SPG."

Still agree? I have never once seen a diver with two SPGs on a single tank/regulator setup. If a redundant SPG was so critical, I'd think two SPGs would be more common.

 

[Altamira]

Exactly. Any piece of gear can fail. I'd consider both SPGs and most transmitters to be quite reliable, but that doesn't change the fact failures can happen. When a failure happens, it now becomes quite important that the failure is recognized. With a transmitter failure, it's likely going to be quite obvious. My experience with SPG failures is more limited, but I did not like the failure mode at all. It was not obvious that there was a problem.


I slightly reworded your message below.

"I think the question you have to answer for yourself and potential dive buddy is whether you are OK with thumbing a really good dive for yourself and buddy should your SPG crap out? Personally, I would really be pissed at myself if I screwed myself and buddy out of completing the dive because I erroneously assumed my precious SPG would not fail, and I was too lazy or overly confident to carry a backup SPG."

Still agree? I have never once seen a diver with two SPGs on a single tank/regulator setup. If a redundant SPG was so critical, I'd think two SPGs would be more common.

From my perspective, if you are renting your dive gear you are likely to only have a SPG, in which case, you have no redundancy on gas monitoring. In that case, you likely will thumb the dive if the SPG fails. However, I was responding to the OP as if he was talking about his own gear. In that case, I think it is prudent to have a backup for at least gas monitoring, depth, and preferably compass. If I am doing multiple dives on consecutive days, I use duplicate AI computers so I can also more closely monitor NDL data. On other rec dives that don’t involve a heavy diving schedule, I use an AI computer with compass and a SPG/depth/compass console. For all dives, I have the redundancy I feel I want/need.

 

[Rearviewmirror]

To each their own, but having an SPG has saved quite a lot of vacation dives for me. The primary thing I haven't seen discussed here is the ease with which you can diagnose the issue that has caused an AI failure. Perhaps I just got very unlucky, but I had what I thought was my Swift AI transmitter fail while diving down in FL. Tried switching out the battery and that still didn't resolve the issue. Mailed the transmitter back to Dive Tronix, and they replaced it - but that still didn't fix the issue as the same thing happened again in Curaçao. Finally figured out that the issue was actually a broken antenna on my Teric.

If I hadn't had a backup SPG I definitely would have lost ~4-6 dives, and in addition would have had to spend time scrambling to figure out replacement gear while travelling.

If you only dive local, and don't mind thumbing the odd dive, then I can see why folks don't see a need for redundancy. However, as a travel diver who only gets a handful of dives per year, the redundancy means all I lose if something fails is some RMV data and the inconvenience of not having air readout on my dive computer.

 

[Belzelbub]

From my perspective, if you are renting your dive gear you are likely to only have a SPG, in which case, you have no redundancy on gas monitoring.

I think you mostly missed the point. For the most part divers don't have redundancy on air monitoring. Most single tank setups only have a single SPG. It's only some divers that have AI computers that have redundancy on air monitoring. No one ever thinks that having a second SPG on a regulator is a must, yet there are those that seem to think it's nuts if you only dive with an AI transmitter.

When hoseless AI was new, there were a lot of problems with reliability. For the most part, that's been solved. I've been diving with AI for many years. My first dive computer was AI, and apart from my backup DC, they've all been AI since. Never felt the need, or encountered an issue where I needed a backup SPG. I still bring an SPG in my SAD kit, but it stays dry.

There are some exceptions from a reliability perspective, but for the most part AI is quite reliable.

To each their own, but having an SPG has saved quite a lot of vacation dives for me. The primary thing I haven't seen discussed here is the ease with which you can diagnose the issue that has caused an AI failure. Perhaps I just got very unlucky, but I had what I thought was my Swift AI transmitter fail while diving down in FL. Tried switching out the battery and that still didn't resolve the issue. Mailed the transmitter back to Dive Tronix, and they replaced it - but that still didn't fix the issue as the same thing happened again in Curaçao. Finally figured out that the issue was actually a broken antenna on my Teric.

As I was reading this, I was trying to guess what type of transmitter and computer you were using. When you mentioned Swift, I guessed it was a Teric. While still pretty rare, there have been more than a few antenna problems on the Teric. But, I agree, if you've had issues with your current setup, a backup does make sense. I use a Perdix and have used a VT4.1 before. Both have been extremely reliable.

This didn't fail underwater, right? Sounded like it happened pre-dive. In that case, I would have simply installed the SPG and did the dive. I'd troubleshoot later. I have kids that dive, and they have the same transmitters, so I could definitely rule out a DC problem. In your case, I'm almost positive your Teric would have read the pressure had you held the Teric right up to the transmitter.