POLL: SPG or transmitter failure - UPDATED TO BE EASIER

[scubadada]

I completed the survey: 0 (SPG) and 1 (xmtr) that ended a dive. However, I've had about 8 SPG failures (of ~1400 trials) that were caught pre-dive. The single xmtr fail (of ~300) was on sidemount with 2 gray PPS transmitters stepping on each other -- my choice to operate outside the designed operational envelope.

What were the SPG failures? Seems like a high rate.

 

[d^2b]

What were the SPG failures? Seems like a high rate.

dunno about inquis, but I had about 4 spool failures over 800ish dives. All on the surface or on entry.

 

[scubadada]

dunno about inquis, but I had about 4 spool failures over 800ish dives. All on the surface or on entry.

I didn't count my spool leaks as failures as they did not prevent me from reading the SPG (read the same as AI computer). I discovered these leaks underwater and replaced the spool after the dive. My leaks have all been a small, steady stream of bubbles, not enough to have a noticeable effect on gas consumption.

From the poll:
"For this, I'm defining "failure" to be anything that occurs which prevents you from accurately determining your tank pressure for the rest of the dive."

 

[d^2b]

dunno about inquis, but I had about 4 spool failures over 800ish dives. All on the surface or on entry.

I did have one SPG that was flooded (and corroded) when I got home. I don't know when/how that happened though.

 

[smashweights]

42
42
0
0

I thought about this earlier this week. I was diving with an instructor who had large bubbles coming out of the back center of her SPG...

 

[inquis]

What were the SPG failures? Seems like a high rate.

Mostly spools, but one bubbling from the rear plug. One wouldn't read past 1800 psi. A new one flooded at the end of its first dive, but it was functional (and returnable).

 

[Centrals]

No experience on transmitter of any form.
Never ever had spg failure(by OP definition).
I did have to replace the spg couple of times because the dial did not return to ZERO.

 

[inquis]

I didn't count my spool leaks as failures as they did not prevent me from reading the SPG

For the poll, I didn't either. I guess my comment was more to say that neither is bulletproof but at least PPS xmitters seem to be less prone to issues in my experience. The definition of "failure" as an inability to read during a dive is a little limiting, in my view, as that's down to minor timing differences.

My son had a slight bubble from a rental reg, but a fortunate twisting of the SPG on-deck caused the O-ring to basically disintegrate before splashing. That same twist underwater would have prevented reading. While I know the gas loss is very small, I'm not certain how that would have affected him. (We did discuss it later.)

 

[stuartv]

I entered 0 for SPG failures, but I've had one SPG assembly "burst" before I splashed and required a new spool O-ring.

I entered 1 for AI failures because I did have a dive where my transmitter died during the dive, but my gas was thoroughly planned and I knew I had enough, so I did not end the dive early. The question specified to count it if I no longer trusted the reading, even if I didn't end the dive early.

The survey does not ask or accommodate dives missed completely because of a failure. E.g. if an SPG blew before splashing and no substitute was available, or a transmitter was dead before diving and no spare battery or substitute was available.

"How many dives have you missed entirely because of a <SPG/AI> failure pre-dive?" seems like a worthwhile question to ask in addition to what's already there. Or maybe "how many dives WOULD you have missed, had you not had the ability to fix or replace with a substitute?"

Another question that is not accommodated is "how many dives did you do where you only found out afterwards that your <SPG/AI> reading was significantly inaccurate?" For example, your SPG stuck at 700 psi and you never realized it during the dive, even though you exited with 300 psi.

I don't think AI really has the failure mode of a "wrong, but believable" reading. At least, not the PPS-style transmitters. Their primary failure mode is simply no reading at all. I think I have seen one or maybe two reports that claimed they got a wildly wrong reading - e.g. 5000 psi or something, where it would be obvious that it was wrong. I don't think I have ever seen a report of a transmitter saying something like 1000 psi when you really have 500.

On the other hand, this is a very real failure mode for SPGs. A needle that sticks and - for example - says 1000 when you really only have 500 is not that common, but failures of that type do happen. And those are (in my opinion) the most dangerous type of failure (of an SPG/AI) transmitter you can have.

The survey doesn't have a way to capture the data on that type of failure, I don't think - and it's a very important piece of the underlying analysis being performed.

 

[lexvil]

I don’t even know how many SPG’s I’ve had to replace, not zeroing and spooled being the most common issue, they tend to get beat up hanging on that hose, one of the reasons I screw transmitters into the first stage.

I had one transmitter quit on me, an older SP type with the 2450 battery, no idea what went wrong because I just replaced it. I only dive wireless air integration for the past several years, SPG is rolled up in my SAD /tool kit but the only time I’ve used it in several year is when I forgot both computers at home.