Spg, AI, both

[Belzelbub]

Before AI did you dive with 2 SPGs?

That is where the redundancy argument falls apart. If AI failures were common today, we’d undoubtedly see a trend away from AI. Instead, we see the opposite. The vast majority of dive computer manufacturers offer AI.

For the most part, diving with both AI and an SPG is familiarity/comfort/laziness. My progression was probably different than most. My first dive computer was a hosed AI console. I got used to having all the information in one place, and got to trust the tech. When that died, I went to hoseless AI, and haven’t looked back.

I’ve also worked in manufacturing for 26 years, with probably 20 or so in electronics manufacturing, and most of that in Quality. So, I trust the tech. Ironically, hardest for me is trusting the batteries. I’m not there yet, as I change the batteries in my transmitters annually, which is well before they actually need changing, but I’ve never had a battery die during a dive or trip, so I don’t see me changing that anytime soon.

I see some parallels with a concealed carry situation. The question always arose among new carriers about how a semiautomatic should be holstered. One piece of advice I got was to carry with no round in the chamber, but the trigger in the forward position. After carrying, make note of how many times the trigger was pulled in the process of holstering, etc. In my case, the answer was never, so I got more comfortable.

For those that aren’t yet trusting AI, by all means carry an SPG, but make a note of how many times you have to go your SPG. Depending on the dive computer and transmitter used, I would bet that the number is zero, or very nearly. I use a PPS transmitter and Shearwater Perdix AI. Both are known for reliability. If either had a history of communication issues, I might have a different position.

 

[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.

 

[Altamira]

Before AI did you dive with 2 SPGs?

Well, no I did not dive with 2 SPGS before AI, any more than I would expect two SPGs or a SPG and a wrist computer on most rental gear today. In fact, when I started diving in 1965, I was cave diving with no SPG or computer because there was no such gear. We just had a single Voit Avalon regulator, a plastic backpack with a 72 cf steel tank with a J Valve, homemade full 1/4" wetsuit and homemade weights, USD mask, snorkel and fins. Did that mean I felt safe, or would not have had a serious problem if something happened to my regulator or air supply? Of course not. Today, we have the availability of all the safety and redundant dive equipment you can ask/pay for. Fortunately, I can afford to dive with as many computers as I like, or an AI and a SPG, or any combination of gear that I might choose. If my AI or SPG fails, I finish the dive. If both fail, I end the dive, and change out whatever failed during the SI. Since I don't dive as much as I would like, when I do get on the boat, I want to make the dives, and do whatever I can to insure that happens.

 

[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.

 

[scubadada]

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.

No, none of these were the Teric antenna problem as I had my ancient Oceanic VT3. Yes, some were my error, still needed to be solved. If you dive enough, you have all the problems. I have had one transmitter hardware failure and one overpressure vavle failure. If you want no interruptions, you have redundancy. If you you don't care, you don't

 

[Belzelbub]

No, none of these were the Teric antenna problem as I had my ancient Oceanic VT3. Yes, some were my error, still needed to be solved. If you dive enough, you have all the problems. I have had one transmitter hardware failure and one overpressure vavle failure. If you want no interruptions, you have redundancy. If you you don't care, you don't

Thanks for the clarification. I wasn’t sure how The VT3 redundancy factored in there.

So, were the other failures (15) due to dead batteries? If so, analyzing the data a bit differently presents a different picture. Just under 1% with all failures. Removing the preventable failures leaves 2, so just over 0.1%. I find that to be an acceptable rate. Certainly better than my SPG failure rate so far.

But, YMMV. A failure of a transmitter will result in a dive interrupted, or a bit shortened depending on when. It won’t result in a canceled dive.

 

[Pressurehead]

OK, I will play.
Muscle memory, when you keep reaching down to unclip it for a quick a look, You might as well have one.
Took it off for awhile, but old habits die hard, so back on it is, and all is good.

 

[OMyMyOHellYes]

What if you have two xmitters on a single tank and only ever wore an SPG on the rental unit for 4 dips for primary certification?? I don't count the little button on the pony bottle: it is only for checking during pre-dive. Don't envision ever using it in the course of a dive even if having to deploy the pony.

 

[gmerick]

Transmitter tucks under the rubber hose retention strap on the inside (next to me). Lollipop hangs free, but the hoses are stiff enough so it lays next to the tank. I've had several transmission dropouts, mostly related to swimming with my hands streamlined back holding onto the lower boltsnaps. Bringing the Perdix back in front restores comms within 20 seconds or so. Gauge is very nice to have if I donate a tank.

 

[hedonist222]

Just AI for about 450 dives now
If I would be on a live aboard, I'd take an SPG in case transmitter/receiver fails
Othewise an SPG is not needed - if it dies during a dive. I will abort.