Safely practicing dive computer violations

[boulderjohn]

You shouldn't have a problem triggering the ascent rate alarm: move your arm up as you go up.

I have heard in the past that programs are designed not to trigger an alarm for something like this because they know that raising an arm quickly simply to look at the computer happens on the majority of dives.

I don't think you need to actually see some of the alarms or warnings to recognize them when they are happening. I once surfaced at the end of a dive during a multidive day, and someone who was with me on that dive (but had been diving with others earlier) said his computer was doing something weird. During the dive it had given him some kind of message that I don't recall now, and it had started counting up minutes. I didn't know that computer at all, but I immediately understood that he had gone into decompression, and he was getting an increasing time to surface because of the now required decompression stop. I immediately took him back down, and we did an extended safety stop. When we got back to the surface, I had him go on oxygen for a while and monitored him.

His original diver training was table based, so he had not had any training on computers in general. He did not know that computers in general will do that. If he had looked at his manual to see how his computer did it, he would have recognized it without having seen it before.

It sounds as if you have enough understanding of what computers do to look up those details in your manual. You are way ahead of people who just buy computers, don't understand what they do in general, and don't look up the specifics for their specific computer.

 

[Compressor]

As others have mentioned already, there are other ways to simulate the alarms.
Go up fast is a problem; it can hurt you physically as you already know. I would bet that when you ascend during your dive, you will inadvertently come up faster than you think and the alarm will go off anyway. Not that you are not skilled but if you want to come up slow, you have to work on it.

Have fun.

 

[Merrydoc]

To be clear, I have absolutely no intention of going anywhere near deco! But I also don't plan on ever running out of air - yet all divers are trained what to do if this happens. I intend to keep practicing air sharing as my diving progresses, because I want to keep that skill sharp even though I hope to never need it.

The display of your computer in deco is quite obvious (word "deco", a short time (e.g., 1 min), a shallow depth (3 m, 10 ft), and can be looked up in the manual.
But why not train deco like you train out of air: without any risk, as a simulation during a dive. Warn your buddy before the dive, then when you start the ascent, signal him with your pinky (meaning "deco"), then a small number (the minutes needed), and another fitting number, see above - the depth to decompress. Ascend normally, stop at the "deco" depth, you wait for the planned time, signal: deco ok, and finish the dive. Maybe download the profile afterwards and check how close you stayed at the "deco depth" over the time - perfect training.

 

[KeithG]

Bth are pretty easy to do. Dive to a certain depth, send your computer up on an SMB. It will trigger. You’ll hear it,

For deco, also easy, do tie it to a line and drop it deep, let it sit there for long enough to go into deco, pull it up.

Do this on a dive devoted to these tasks specifically. Keep it shallow, short, and stick with your buddy so you can follow their computer during your short dive.

As indicated you can safely accomplish all these things with out ever getting yourself wet. With a long weighted rope off a deep dock you can send your computer down for as long as you want and you can bring it up as fast as you want.

A more flexible and less messy method would be to use a pressure chamber. Your LDS may be able to direct you to one, or you can make a simple one for less than $100. There are thread(s) here about DIY pressure chambers. You can then do the tests in the comfort of your own kitchen.

 

[dmaziuk]

I have heard in the past that programs are designed not to trigger an alarm for something like this because they know that raising an arm quickly simply to look at the computer happens on the majority of dives.

Somebody on the programming/design team has to decide how long to wait before triggering the alarm: too long and you may be looking at AGE, too short and everyone's annoyed with incessant beeping. (If ascent rate is not programmed into the model, they also have to decide how long to let it stay alarmed before switching to gameover mode -- or not, if it's a shearwater.) I've plenty of "momentary" rate yellow triangles in my logs that didn't trigger the beeps on the dives, but it's fairly easy to go over the threshold and make my leonardo beep. Leonardos "beep too much" and you can't turn it off (I'm not convinced it's a bad thing). No idea how easy it may be with mares.

 

[RainPilot]

Just bear in mind to do any of these simulation exercises on the last dive of the trip / week, most computers will lock you out if you do enough weird things, sending one up on an SMB will do the trick.

 

[tursiops]

Just bear in mind to do any of these simulation exercises on the last dive of the trip / week, most computers will lock you out if you do enough weird things, sending one up on an SMB will do the trick.

Depends on the computer.

 

[RainPilot]

Depends on the computer.

True enough. It's why I love my Shearwaters.

 

[KeithG]

Depends on the computer.

That is why I suggested using a chamber. It is very easy to quickly "pump your computer down" well past recreational limits and then rapidly bleed off the chamber to make a missile like ascent. Saw tooth profiles are also easy to accomplish.

All with out getting yourself wet.

 

[shawnhar]

Back from practice dive this morning. I tried moving my arm rapidly from reach-down to reach-up, but was unable to trigger the rapid ascent alarm. Ah well.

I think it's a shame there aren't more accessible ways to practice these things. As the Hawaii missile alert recently demonstrated, there is value in being able to rehearse using technology in situations more realistic than just reading manuals, but without being anywhere near to an the actual live emergency situation