Why I am getting a backup pressure gauge for my hoseless air integrated wrist dive computer.

[dmaziuk]

Too bad that DTR computation does not consider that which is probably the most important parameter for such a computation and, instead, has to assume you plan to continue your dive at your current depth.

Yes. A crystal ball in the tank pod that tells you in 5 minutes you're gonna run into a free-swimming frogfish at 22 metres and a cloud will pass overhead, so pre-set your white balance now. When they start selling these, I want two.

 

[dmaziuk]

While it is a good practice to agree on turn pressures, it would be even better to agree on turn times as well, because each diver has a rough idea of how long they can stay down, with whatever cylinder they happen to be diving.

IME if you go for a "package" with a decent dive op, by day 3 at the latest DMs too will have a rough idea of who can stay down how long. They can get close enough on total runtime and point out the spot where we're likely to surface at pre-dive briefing.

 

[idocsteve]

I have always dived with a backup computer, an Oceanic Geo 2, or, more recently, a Dive Rite Nitek Q, and a backup SPG.

This exactly what I'll be doing. Primary will be my AI VT Pro wrist computer, backup mini analog SPG gauge, and a spare VT pro AI on a boot mounted with a retractor, which either me or my girlfriend can use if one of our primary's fail. The spare will be set to read one of our transmitters (probably mine since I do more dives than she does) so we'll have a third redundancy there. She now has a backup analog SPG as well. I know you're "not supposed to share" a computer between two divers but since I'll be wearing the spare and she always dives the more conservative profile I think we'll be ok in the event she needs to use it.

Nobody is saying to leave the spg at home, just on the boat in your kit with the allen wrench and the wrench required to add it to your reg if needed. That would have worked in each of the instances you mentioned and that's 875 dives without the minor annoyance of another hose and a gauge clipped off.

I totally get it, and I am thinking about this option, but of course you may need to scrap one dive if the primary fails right in the middle and you refuse to dive without knowing your gas remaining.

It's also an option when the regulator first stage only has one HP port (like my girlfriend's does) and you don't want to get involved with either buying a new first stage or adding an HP splitter (which I did).

Last week I purchased two analog SPGs online, one was a "mini" and one was regular size, both single console. They didn't look much different in the pictures. Turns out to be a big difference in the sizes. The small one will tuck away very nicely.

 

[tbone1004]

@idocsteve the situation where calling the dive early is mitigated with proper gas planning. You may not max out your dive, but there is no reason to scrap it. For recreational diving as well, you can also gauge your consumption based on your buddy. I.e. if you have similar SAC rates to your buddy, then during pre-dive you can say "if my AI fails, then please thumb the dive 200psi before xx pressure". The xx being your agreed upon ascent pressure. You'll have already set your rock bottom pressures, and there is enough buffer in there to not need to call the dive early because of a failed transmitter

Best first regulator, DIY service

 

[BoltSnap]

I was not getting cylinder pressure on my AI. Turns out my 7 year old transmitter has failed.

Don't you get a low battery warning for the transmitter before this happens and the transmitter goes completely dead? I don't know how long the battery in the PPS transmitters lasts but I'd imagine that I'd replace them every 2-3 years just to be on the safe side.

 

[scubadada]

Don't you get a low battery warning for the transmitter before this happens and the transmitter goes completely dead? I don't know how long the battery in the PPS transmitters lasts but I'd imagine that I'd replace them every 2-3 years just to be on the safe side.

Not sure which of the 2 episodes you are referencing. The first was entirely my fault, after a period of inactivity I took my primary computer diving without 1st checking it. The battery had insufficient power left to run the computer. A battery change was all that was needed.

In the most recent episode, my 7 year old transmitter simply has stopped working, it is not a battery problem. The computer does have a battery indicator. The transmitter battery can be tested by a button push on the computer. I generally change the computer battery as soon as the low battery indicator comes on and I replace the transmitter battery at the same time. The transmitter battery has never tested low at the time of battery change.

 

[BoltSnap]

Not sure which of the 2 episodes you are referencing. The first was entirely my fault, after a period of inactivity I took my primary computer diving without 1st checking it. The battery had insufficient power left to run the computer. A battery change was all that was needed.

In the most recent episode, my 7 year old transmitter simply has stopped working, it is not a battery problem. The computer does have a battery indicator. The transmitter battery can be tested by a button push on the computer. I generally change the computer battery as soon as the low battery indicator comes on and I replace the transmitter battery at the same time. The transmitter battery has never tested low at the time of battery change.

I was referring to the transmitter episodes, I thought it was a battery issue. Sorry, I misunderstood what you said.

I have a hoseless AI wrist computer with transmitter, D9/Vyper Air, and a backup Cobra (hose AI) for backup. I don't remember having to use the back as a backup due to fault with the wrist computer but I have set one with metric units and the other with imperial units when I left the US to live in the Middle East just to get used to going with the metric units when underwater. I'll be getting new computers soon (Ratio-computer) and possible a more liberal AI in console computer (probably the PPS) when conditions allow here in Libya.

 

[Joneill]

@idocsteve the situation where calling the dive early is mitigated with proper gas planning. You may not max out your dive, but there is no reason to scrap it. For recreational diving as well, you can also gauge your consumption based on your buddy. I.e. if you have similar SAC rates to your buddy, then during pre-dive you can say "if my AI fails, then please thumb the dive 200psi before xx pressure". The xx being your agreed upon ascent pressure. You'll have already set your rock bottom pressures, and there is enough buffer in there to not need to call the dive early because of a failed transmitter

Best first regulator, DIY service

Or you can avoid any drama at all by just carrying a redundant SPG. However, for some reason this approach appears to really upset some here: Oh, the horror and complexity of just leaving your SPG in place when you add an AI transmitter. Of course, some also feel that the extra 2 seconds it takes to clip that SPG off to your hip D-ring is annoying...

Folks also seem to forget that many of us are really "solo" divers (have non diving spouses/partners or travel solo), so we don't really have a clue as to our "buddies" SAC and would not trust what an insta buddy stranger might tell us. In fact, most times we don't even have a buddy - we're diving as a group.

I honestly don't get all the pushback. I can plan my gas to the nth degree and that plan can go upside down once underwater for a variety of reasons. While I can plan contingencies and estimate (still just an educated guess) my remaining gas, why would I still not prefer to have access to EXACT knowledge of my gas via a backup? That way I can continue the dive and get my money's worth versus aborting earlier based on a plan that had a buffer I might not have needed or assumptions that were more conservative than reality (as assumptions should be).

 

[RayfromTX]

Or you can avoid any drama at all by just carrying a redundant SPG. However, for some reason this approach appears to really upset some here: Oh, the horror and complexity of just leaving your SPG in place when you add an AI transmitter. Of course, some also feel that the extra 2 seconds it takes to clip that SPG off to your hip D-ring is annoying...

Folks also seem to forget that many of us are really "solo" divers (have non diving spouses/partners or travel solo), so we don't really have a clue as to our "buddies" SAC and would not trust what an insta buddy stranger might tell us. In fact, most times we don't even have a buddy - we're diving as a group.

I honestly don't get all the pushback. I can plan my gas to the nth degree and that plan can go upside down once underwater for a variety of reasons. While I can plan contingencies and estimate (still just an educated guess) my remaining gas, why would I still not prefer to have access to EXACT knowledge of my gas via a backup? That way I can continue the dive and get my money's worth versus aborting earlier based on a plan that had a buffer I might not have needed or assumptions that were more conservative than reality (as assumptions should be).

Throughout this discussion, I and others have said that each individual should do what they feel comfortable with and each of us decides these things for ourselves. Your first paragraph is what pushback looks like. In it you exaggerated the statements of others that have a different point of view and ridiculed them for their position.

 

[Joneill]

Throughout this discussion, I and others have said that each individual should do what they feel comfortable with and each of us decides these things for ourselves. Your first paragraph is what pushback looks like. In it you exaggerated the statements of others that have a different point of view and ridiculed them for their position.

My apologies - it was not my intent to ridicule anyone, but there seemed to be exactly that coming across from several towards the concept of keeping the SPG as a AI backup. I was just trying to highlight how relatively minor the reasons that were being thrown out for dumping redundancy are for a rec diver like myself.

I also think I've made a valid case for why a backup SPG is still a good idea, regardless of how well you think you may know your SAC under different scenarios and may have predicted actual conditions and potential issues - especially for relatively new divers like me (50 dives so far).

Of course, it's up to each person to decide what information they are comfortable doing without during a dive. Personally, in the event of an AI failure, I'd much rather have a way to still know my true remaining air supply than have to rely on an estimate. I'll leave it at that - and, again, no offense was intended.