Spg, AI, both

[Belzelbub]

Have AI or have an SPG. Having both is the worst option.

It's funny how basically everyone agrees that it's fine to have just one SPG and no AI. But, some people will say it's not okay to have AI and no SPG. Essentially, that is hypocritical.

Yes, AI can fail. But, so can an SPG. Your procedure following a failure is the same, either way.

These days, when talking about a PPS or Shearwater transmitter, I don't see any evidence that SPGs are more reliable than AI.

Exactly. I’ve never seen a diver run two SPGs off of a single reg. If it’s fine to run just one, it’s fine to run just AI.

Mechanical parts can fail, electronic parts can fail. A failure of a pressure gauge (SPG or AI sensor) is not necessarily a cause for concern if you’ve been watching your gas. Electronic parts often fail on startup, and when they do fail, it’s usually hard to miss. A blown OPV will have a lot of bubbles, and no communication. A dead battery or otherwise dead transmitter (flooded, etc.) will also have no communication. A failed SPG can stick at 1500 psi, that might not be detected right away.

 

[Edward3c]

Adding an SPG also makes it where you can put your rig together and check your SPG to verify your cylinder is full - forgetting your computer or not verifying that your computer and AI is working. I used to have a button gauge on my single tank reg set. I took it off so that it forces me to get out my computer to verify cylinder pressure before a dive. That, in turn, ensures that I don't forget my computer (e.g. leave it in the truck when my boat heads out) and that my AI does not have a dead battery or some other failure.

The times I forgot the computer I had already used it to confirm tank pressure etc. I just didn’t put it on after putting my drysuit on. Leaving the transmitter at home has happened twice over the last 5 years.

 

[stuartv]

The times I forgot the computer I had already used it to confirm tank pressure etc. I just didn’t put it on after putting my drysuit on. Leaving the transmitter at home has happened twice over the last 5 years.

After I check, I fasten my computer to a D-ring on my BCD, so that I can't "forget" it. At worst, I just have to don it in the water.

I never take my transmitter off my reg set (not sure why one would), so I'd have to forget my whole reg set.....

 

[Jersey1971]

Ok, I’ve seen a couple of references to people leaving their transmitters at home or in the car. I leave mine permanently on my first stage. Is there a reason to disconnect? I assume it goes to sleep once pressure is disconnected, and this is confirmed by long battery life.

 

[Belzelbub]

The times I forgot the computer I had already used it to confirm tank pressure etc. I just didn’t put it on after putting my drysuit on. Leaving the transmitter at home has happened twice over the last 5 years.

Multiple regs, or do you regularly remove your transmitter from your 1st? If the latter, why?

Ok, I’ve seen a couple of references to people leaving their transmitters at home or in the car. I leave mine permanently on my first stage. Is there a reason to disconnect? I assume it goes to sleep once pressure is disconnected, and this is confirmed by long battery life.

No reason that I can think of. My transmitter lives on my 1st. I remove it only when I take my reg in for service. While the reg is at the shop, I change the transmitter battery and o ring. Other than that, it’s on my 1st.

If I arrive at the dive site and left my transmitter at home, I’m not going diving asi I’ve left my regulator at home.

 

[scubadada]

@Belzelbub

I've used my SPG on 17/1845 dives, a little under 1%. To not end a dive or a series of dives is invaluable. Sometimes more valuable than others. Perhaps when you increase your experience.

Maybe, or maybe not. As I recall a number of those were self inflicted (dead battery) and some others were due to antenna problems. The antenna issues seem to occur a bit more often with the Teric than with my Perdix. For now, I have a good amount of confidence with my gear. While, I don’t have as many dives as you, statistically, I should have a few dives with a transmitter/comms failure. I don’t. I have zero. I have ”seen” only one failure, and it was during initial test. Never under water. I can’t say the same about my experience with SPG failure. I have seen that underwater.

As I said, with different gear or different experiences, I would reevaluate. Nothing so far has pointed me to changing what I do. I check my gas supply regularly, and usually dive off my own boat, so likely not typical. If a buddy were to complain about me having to surface for a swap, there’s a solution for that.

My dives are recreational, and primarily involve hunting. Streamlined is important. The surface is easily within reach. Should I have a transmitter failure that is not preventable, I may re-evaluate.

Fair comments from @Belzelbub

I have only kept my backup use stats since I started diving my Oceanic VT3 in 2010. I have had a backup SPG since then. I dived a non-AI backup computer until 2019, when I bought my 1st Teric.

The 17 dives where I have used my SPG backup include:
2 dives with dead battery in VT3, entirely my fault, used backup computer and SPG
2 dives with a dead transmitter battery, entirely my fault, backup SPG used
5 dives with a transmitter hardware failure, backup SPG used, transmitter replaced
2 dives, transmitter not changed over to reg set used, my fault, backup SPG used
1 dive, transmitter not changed over to loaned reg set, 1st stage leak, backup SPG used
5 dives, transmitter OPV failed and flood, backup SPG used, transmitter replaced

So, 6/17 of these episodes were my fault, the others not. These stats do not include the problems I have had with my Terics as I had my VT3 AI computer to back up the Teric failures.

Teric owners, have you required repair or replacement service?

All that would resonate with me IF Terics were dying in such a way that they were causing people to have to end dives early. Or even to miss dives. It's not like they don't work. The problem that many of us have had is that the battery starts to run down faster than it should when it is...

scubaboard.com

I would have required a backup computer and SPG to cover the Teric black screen. I would have required a backup SPG to cover the 3 Teric antenna failures. The last Teric antenna failure was on a liveaboard in Malpelo and occurred on dive 12 of 21.

I have never cut a dive short or lost a dive in a series due to computer or transmitter failure. The only problems I have had with SPGs were minor gas leaks taken care of by replacement of the spool.

To each their own. @stuartv I've not thought of myself as a hypocrite

 

[stuartv]

Fair comments from @Belzelbub

I have only kept my backup use stats since I started diving my Oceanic VT3 in 2010. I have had a backup SPG since then. I dived a non-AI backup computer until 2019, when I bought my 1st Teric.

The 17 dives where I have used my SPG backup include:
2 dives with dead battery in VT3, entirely my fault, used backup computer and SPG
2 dives withe a dead transmitter battery, entirely my fault, backup SPG used
5 dives with a transmitter hardware failure, backup SPG used, transmitter replaced
2 dives, transmitter not changed over to reg set used, my fault, backup SPG used
1 dive, transmitter not changed over to loaned reg set, 1st stage leak, backup SPG used
5 dives, transmitter OPV failed and flood, backup SPG used, transmitter replaced

So, 6/17 of these episodes were my fault, the others not. These stats do not include the problems I have had with my Terics as I had my VT3 AI computer to back up the Teric failures.

Teric owners, have you required repair or replacement service?

All that would resonate with me IF Terics were dying in such a way that they were causing people to have to end dives early. Or even to miss dives. It's not like they don't work. The problem that many of us have had is that the battery starts to run down faster than it should when it is...

scubaboard.com

I would have required a backup computer and SPG to cover the Teric black screen. I would have required a backup SPG to cover the 3 Teric antenna failures. The last Teric antenna failure was on a liveaboard in Malpelo and occurred on dive 12 of 21.

I have never cut a dive short or lost a dive in a series due to computer or transmitter failure. The only problems I have had with SPGs were minor gas leaks taken care of by replacement of the spool.

To each their own. @stuartv I've not thought of myself as a hypocrite

I don't think of you that way, either. My apologies if it came across to you in that way. I said:

It's funny how basically everyone agrees that it's fine to have just one SPG and no AI. But, some people will say it's not okay to have AI and no SPG. Essentially, that is hypocritical.

I don't think you are a person who would say it's not okay to have AI and no SPG. I.e. it is unsafe to dive with only AI. I don't think you would say that. Or even that it is simply "not smart".

Also, for the record, your data on this is awesome. But, as presented, I think it might be slightly misleading. For example, your post makes it sound like on 5 different occasions, you have had a transmitter OPV fail. I *think* you mean that it happened 1 time and resulted in using your backup SPG for 5 dives, until you got the transmitter replaced. So, at most, 1 of those would have been cut short or missed, but not all 5.

I *think* from what you posted, if you had a backup transmitter with you, available to swap out, and a second AI computer and no SPG at all, you still would have been able to do all the same dives.

Obviously, having a backup computer is recommended, really, at all times. Not necessary, but recommended. Especially if you're going on a dive trip of multiple days. If you're going to use AI, then having the backup computer be AI-capable and compatible with your transmitter only makes sense.

Having either a backup SPG or transmitter also makes sense.

I think the real question is: How useful is it to have your backup (SPG or transmitter) installed on your 1st stage alongside your primary transmitter? If you had not had the backup SPG already installed on your reg set, THEN how many dives would you have missed or cut short because of an AI problem? I.e. by having an SPG already installed on your reg, alongside your transmitter, how many dives were saved?

I think we're talking about 2 or 3? Maybe 2 or 3 more, if you count ones where you had a dead battery? Or maybe having a backup SPG ready at hand, but not installed, would have been sufficient and you would have done all the same dives.

The possibility of missing or cutting short 5 or 6 dives out of 1800 does not concern me (just me and my personal choice) enough to add an SPG to my rig. I have 2 AI-capable dive computers and carry a spare transmitter with me. And I keep up with my transmitter battery changes...

 

[Edward3c]

After I check, I fasten my computer to a D-ring on my BCD, so that I can't "forget" it. At worst, I just have to don it in the water.

I never take my transmitter off my reg set (not sure why one would), so I'd have to forget my whole reg set.....

The ports on my first stage mean a directly attached transmitter would easily be mistaken and used as a handle. Hence it’s on a 15in hose with a quick release.

I have no issues, or ask you to change your configuration to replicate mine. So why are you so adamant I change to the way you do things. With over 2k dives I’ll continue to configure my kit as I see fit.

 

[scubadada]

My friend @stuartv

We have known each other for a long time. We know each other pretty well, I'm sorry we still haven't had the opportunity to dive together. I don't think my description can easily be misconstrued. I haven't carried a backup transmitter with me on trips, that can be easily remedied. I dive with a setup that I am comfortable with, I'm sure that is true for you too.

 

[stuartv]

The ports on my first stage mean a directly attached transmitter would easily be mistaken and used as a handle. Hence it’s on a 15in hose with a quick release.

I have no issues, or ask you to change your configuration to replicate mine. So why are you so adamant I change to the way you do things. With over 2k dives I’ll continue to configure my kit as I see fit.

I'm not sure how I have made it seem that I am adamant - or even concerned - that you change to the way I do things. But, I am self-aware ENOUGH to know that I don't always come across the way I meant it in my mind.

I did not intend at all to suggest that you must change. I only offered my explanation of what I do, in case it helps you (or anyone else) in any way. What I do seems (to ME, in my own mind) to mitigate the issues that you described having had in the past.

My apologies to you if I made it seem like I am adamant that you change.