Air Integrated Computer Help Needed

[MauiScubaSteve]

I have been diving with computer since right after becoming an instructor, spring '01. First one was Uwatec Aladdin Pro (stolen), now Suunto Vyper, both not air integrated (AI).

Now as a guide I find myself in the water with many AI divers of various brands. My number one job is to insure the safety of my guests, many of whom do not know their own computer at all.

In a perfect world, all certified divers would follow the briefing and tell me when they are approaching the pressure they need to be on the ascent line in order to do the required Safety Stop (SS) and get on the boat with the 500 psi the captain wants to see. That does not always happen and occassionally divers are not back on the line in time to finish the SS above 500 psi.

Recently, a diver at 15' starting the SS was ~400 psi, and when my coworker returned the dropped dive light she had to hold him down, deflate the over-full BC and plug him in to her alternate to bring the eyeball size down from half dollar and the breathing rate down to post half mile run.

According to her, part of this panic could have been due to the computer flashing 0 Minutes Remaining as the biggest number on the computer, although 360 psi was also shown bottom corner. If calm, this diver did the dive with a SAC that would have only consumer just over 100 psi at SS, but task overload and scary computer info seem to have pushed him into hyperventilation.

Here's my question for all you AI divers that know your computer; When does the 0 minutes remaining happen on your computer (if you know) and what other pertinent info do you think a guide should know about your computer when diving with someone who doesn't understand that model.

Both I and my future noob guests thank you in advance for this valuble education!

 

[FishOutUvH2O]

I'm new to diving, but know my computer. It's an Oceanic VT3 air-integrated. "0 minutes remaining" depends on what particular factor is controlling the dive time remaining (DTR) counter. It could be based on air time remaining (ATR), no decompression time (NDC), or oxygen accumulation time (OTR). In any case what "0 minutes remaining" means is that I've reached the limit of my "fun time", not the limit of the controlling factor. The computer has already calculated in the time and air needed to make a safe ascent w/a SS. So just because I see "0" for DTR, I'm not going to panic thinking I'm going to run out of air or that I just overloaded my tissue with nitrogen. It would just mean I've taken the dive to it's very limit and without delay, it's time to start ascending to the SS.

My VT3 is pretty easy to understand. If there's a problem like LOA/OOA, it will be flashing the words "LOW AIR" blinking wildly and making all kinds of noise. My wife's Uwatec Galileo Sol is pretty much the same way. Again, just because it may indicate "0" for DTR doesn't mean you're in deep do-do, it just means play time is over and it's time to go up. The only real info a guide would need to know is that if it's making a lot of noise and blinking, some event has triggered an alarm and there may be something seriously wrong, and also what psi is left in the tank. On both of our computers the psi is prominent with a number and the letters psi.

 

[laurelgsc]

You set your pressure that you want to come up. I think the default is 500 if you don't mess with it. His computer was flashing 0 air time because he had less than 500 PSI. It comes down to knowing your computer. People should take the time to understand what their computers do under many situations including what to do if you go into deco accidentally. Occasionally these computers will loose their link, but if you wait a couple of seconds it will pick it back up. That's the only difference I can think of. Hope this helps.

 

[John512]

Basically what the others said, with my VT3 if you have it set at 500 PSI to arrive back at the surface with it calculates the time based off that. They key is that it also calculates the amount of time to safely swim up, do a 3 minute safety stop, and break the surface with that 500 PSI remaining. It calculates the time based off previous 60 (maybe 90) seconds of air consumption so the number will go up and down if a divers respiration is changing.

You can also set a turn around pressure where it alerts you when it is reached as well as a dive time alarm.

Overall I love diving air integrated, granted I have only ever done that, but knowing your equipment is critical as that diver saw...

 

[ligersandtions]

With my computer, it does some calculations based on your breathing pattern over a specific period of time (maybe the last 60 seconds....although I'm not 100% sure) and the pressure you have left in your tank (I'm under the assumption that it does not base it solely on the pressure left in the tank as 500 psi with a low pressure steel has a different volume than 500 psi with an Al 80 which has a different volume than....you get the point).

Last weekend I went out and purged my tank down to 500 psi to check my weighting at 15 feet (basically to get correctly weighted for a safety stop at the end of a dive). Directly after I finished purging, my computer was freaking out at me because it thought I was out of air, 0 minutes left.....then I breathed normally on it and checked it again and all the sudden, it was convinced I had 40 minutes of air left.

So, it's not a pressure reading that it's based on....but your breathing pattern and how much air you are consuming. Obviously, if you are panicked or over-exerting yourself, it's going to be convinced you have much less air time left than you may (it's not likely you will not continue like this, and once you calm yourself down, it'll jump back up to a more reasonable, non-zero number). However, I know from first-hand experience that it is a little unnerving to see only a few minutes of air time left when you are under 80 feet of water....

 

[don Francisco]

I'm not a DM, nor do I want that responsibility, especially as new equipment makes managing a dive with lots of different folks more complicated.

As you can see from the replies so far, different computers show similar data differently. As a DM, there's no way you'll be able to learn how each computer displays data, what exactly it means, and then remember which brand does what, at depth. It's just too much to ask.

Obviously everyone using a dive computer should read the manual and learn how to use it, but today it may be too much to expect. I'll never understand why folks who can't program a VCR insist on buying the most sophisticated computer with every conceivable feature, and then dive with no idea what the screens look like and what the data means.

Case in point ---I was diving with a pickup buddy who had a Suunto computer, when towards the end of our second dive it started beeping and flashing ascend, which is how Suunto displays that you're at the NDL, usually showing a ceiling for a safety or deco stop.

Sure enough when it said ascend he did just that, about as fast as his fins could propel him. Went directly to the surface, didn't manage his ascent rate, didn't stop at the ceiling, didn't do a safety stop (which might have made sense since he was at an NDL), didn't pass go, didn't collect $200.

As a DM, you might need to ask your charges not only whether they have a computer, but if they're familiar with it.

 

[I Dive]

Yep, that sounds familiar. My computer does the same exact thing. I can go from 30 minutes of remaining air to 65 minutes by slowing down my pace and controlling my breathing. It's not an issue any more now that I have dives under my belt and have learned I don't need to suck half the tank on each breath, but when I first started the computer wasn't giving me much time...

 

[alcina]

Here's my question for all you AI divers that know your computer; When does the 0 minutes remaining happen on your computer (if you know) and what other pertinent info do you think a guide should know about your computer when diving with someone who doesn't understand that model.

I dive UWATEC Aladin Nitrox Air integrated wrist mount.

I think my 0 minutes comes up at like 45 bar or so...it obnoxiously beeps at this stage. Strangely, it stops beeping at about 25 bar. I guess it figures if I've happily ignored it for the past 15 or so minutes, I'm not likely to care

As for what a guide should know, we use guides for our divers here and our guides are not expected to know every single thing about every single computer. It is the diver's responsibility to monitor air, not the guide's.

Perhaps instead of trying to find ways to increase your babysitting skills, you also need to concentrate on creating a better dive brief procedure and diver evaluation before the dive. Our guides use the time during gear set up to actually talk to the divers and it's pretty amazing how many potential problems can be caught and dealt with.

Although having a diver in a group not inform of remaining pressure can happen, it's not usual or the norm here at all. Underwater most of our guides have a system of asking for people's air during the dive - this helps them determine turn around points and gives them a sense of who has what left. It virtually eliminates people getting into a very low on air situation too far away from the mooring line and it is unobtrusive to the dive group mostly.

 

[Blackwood]

Yah, many of them use instantaneously computed consumption rates, so if you suddenly start pulling down 3CFM/atm, it's going to freak out.

 

[hudson]

Obviously everyone using a dive computer should read the manual and learn how to use it

You are assuming the manual actually tells you wth the air remaining time is. Mine certainly doesn't. The number is so worthless, it doesn't even tell the people who could actually use it (newbies not comfortable with their gas management yet) what it is!!