Do you really understand your computer, or is it a threat to you?

[CaptSaaz]

Hey Don, great thread to start.
I picked up a computer just as I was getting certified, Oceanic Versa Pro. Being a tech/nerdy kinda guy I read the manual over a couple of times while I played with the computer and tried to understand stand it first before getting wet. I set the defaults to what I wanted and understood that I will have to reset them if and when I dive EAN.
They are a bit more complicated than I first thought but not overwhelming so. And I still do my tables after the dive. I take the max depth and dive time from the computer and run out the PG and SI. Now after a few dives I'm glad I have an analog depth gauge on my console and want to add a dive watch just for the redundancy. Working with the equipment I do at my job, air traffic control, you quickly learn the necessity of having backups to your main computer processors, radios and comms.
Dive computers are great instruments to use but I think can be dangerous if they are not fully understood or if they break down. I also set the defaults to warn/beep BEFORE I hit the yellow, while they are still in the green and max depth BEFORE I get there.
Cheers mate.

 

[RonFrank]

I purchased an Aeris Atmos II, and read the manual front to back and then did a bunch of simulations. I thought I had it down, but last night I went to practice my skills with it (diving this weekend), and while I retained much of what I had learned, I found that I had already forgotten things. Back to reading the manual!

Computers are great tools, and studies indicate that diving safety has improved with the computer sited as the main reason. However the Atmos II will definately allow one to dive unsafely, and merrily record and display the data.

The plastic cheat sheet is good for commonly used things, but very incomplete. I carry the owners manual in a plastic zip lock in the dive bag with my log and wheel.

Some of the default alarms are very liberal. If memory serves, the default alarm for reaching the NDL is activated in the red, not the yellow. This is user selectable. This may work for many divers as they run out of air before hitting the NDL, but one should understand this very important alarm, and set it.

The bottom line is that puters are great, but people better know what this wiz bang device is doing, and how to use it properly.

Based on my very limited diving experience, it seems that too many divers rely on Divemasters and a very limited understanding of computers to remain safe. The fact that one can rent a dive computer, and be using it a few hours later with next to zero instruction on how these very feature laden devices operate indicates that people will place trust in the computer without understanding the default settings.

If the thing goes off, and various displays are flashing with counters running, how would someone know what the thing is telling them without knowing exactly what each display means given that most displays can provide different readings based on the mode it is in, and what limits have been reached?

Ron

 

[kalvyn]

Based on my very limited diving experience, it seems that too many divers rely on Divemasters and a very limited understanding of computers to remain safe. The fact that one can rent a dive computer, and be using it a few hours later with next to zero instruction on how these very feature laden devices operate indicates that people will place trust in the computer without understanding the default settings.

First off, I want to make the point that I am not against the use of dive computers. They're a great tool for the recreational diver, in my opinion, with the proper understanding of not only now their computers work, but the why behind them.

My concern about them comes from people not understanding the deco theory and reasoning behind their computers, and just blindly following them, believing they're safe as a result. Perhaps these folks aren't thinking about how riding the computer's NDL every dive perhaps isn't truly a good idea, or that their computer's 30 fpm ascent rate alarm is perhaps not really all that conservative, when you get right down to it.

Take a dive to 100 fsw... most computers will let you dive to 100 fsw for ~20 minutes (my Mosquito gives me 17 minutes in Plan mode right now). You leave after 16 minutes (riding the NDL) and come up to 15 fsw at 30 fpm (and maybe the thing beeps at you once for exceeding the ascent limit...), stopping for 3 minutes. Once the safety stop is over, you pop to the surface and call it good. Your computer's happy, no violations, and you never exceeded the NDL.

In my opinion, that's not a safe dive. I personally would spend a minute or so at about 80% of my max depth, then stop at 30, 20 and 10 fsw. I might even stay at 20 fsw for a while if there's cool stuff to see. I would also make sure that before I ever got into the water that I had enough gas to dive the profile I prefer for a dive to 100 fsw for that length of run-time.

Those sorts of things aren't done for me by my Mosquito. It would be perfectly happy with either dive profile, quite frankly. Only by being better educated, not only in the use of my computer but in diving in general am I truly a safer diver.

One last thing... the dive to 100 fsw profile with an ascent to 15 fsw is real. I saw this very thing diving the Hilma Hooker in Bonaire this past February, and there were people on the boat with us that were wondering why their computers were in the yellow still, even after their 3 minute safety stop...

Jimmie

 

[ShakaZulu]

Most recreational divers have no idea what their computors is telling them (especially when they exceed the NDL limit), they are just lucky there is a DM in the group, or someone who knows what they are doing.

The problem is in the creation of the dive plan, that is so rarely done. Rock-Bottom times aren't discussed and don't get me started.......

 

[flounderboy]

The problem is in the creation of the dive plan, that is so rarely done. Rock-Bottom times aren't discussed and don't get me started

.......

VERY TRUE !!!!!!!!


Dive safe

mark s

 

[StSomewhere]

Take a dive to 100 fsw... most computers will let you dive to 100 fsw for ~20 minutes (my Mosquito gives me 17 minutes in Plan mode right now). You leave after 16 minutes (riding the NDL) and come up to 15 fsw at 30 fpm (and maybe the thing beeps at you once for exceeding the ascent limit...), stopping for 3 minutes. Once the safety stop is over, you pop to the surface and call it good. Your computer's happy, no violations, and you never exceeded the NDL.

In my opinion, that's not a safe dive. I personally would spend a minute or so at about 80% of my max depth, then stop at 30, 20 and 10 fsw. I might even stay at 20 fsw for a while if there's cool stuff to see. I would also make sure that before I ever got into the water that I had enough gas to dive the profile I prefer for a dive to 100 fsw for that length of run-time.

Those sorts of things aren't done for me by my Mosquito. It would be perfectly happy with either dive profile, quite frankly. Only by being better educated, not only in the use of my computer but in diving in general am I truly a safer diver.

And yet anyone who's spent more than a couple hours reading dive mags and surfing the web assumes that they should be getting that type of dive profile if necessary from their expensive, new RBGM computer. Huh...

Any recommendations on a book to better understand decompression theory, ceilings, etc.?

 

[jbisjim]

Any recommendations on a book to better understand decompression theory, ceilings, etc.?

I have mending the bends which goes pretty deep. Not a long book but straight forward

 

[DandyDon]

Good post there, Kalvan. I do want to speak to a couple of good points you made....

Take a dive to 100 fsw... most computers will let you dive to 100 fsw for ~20 minutes (my Mosquito gives me 17 minutes in Plan mode right now). You leave after 16 minutes (riding the NDL) and come up to 15 fsw at 30 fpm (and maybe the thing beeps at you once for exceeding the ascent limit...), stopping for 3 minutes. Once the safety stop is over, you pop to the surface and call it good. Your computer's happy, no violations, and you never exceeded the NDL.

In my opinion, that's not a safe dive. I personally would spend a minute or so at about 80% of my max depth, then stop at 30, 20 and 10 fsw. I might even stay at 20 fsw for a while if there's cool stuff to see. I would also make sure that before I ever got into the water that I had enough gas to dive the profile I prefer for a dive to 100 fsw for that length of run-time.

Agree that. With the Pleagics I've been using for examples here, the diver would surface high in Yellow Caution zone, I think. I don't have my Versa Pro with me here now, and besides - sim dives ran at 3300 feet elevation aren't a good comparison.

The deeper stops, and/or a long stop at 15-20 feet would be needed to get back into the Green zone strongly suggested. I was referencing this in the second part of my orginal post.

Like this...

One last thing... the dive to 100 fsw profile with an ascent to 15 fsw is real. I saw this very thing diving the Hilma Hooker in Bonaire this past February, and there were people on the boat with us that were wondering why their computers were in the yellow still, even after their 3 minute safety stop...

 

[RICoder]

I think I am getting that the general concensus is basically my own feeling on the matter...but PLEASE let me know if I'm off...

I always and only dive with a computer, but I know the theories behind deco. In my oppinion, a person armed with the knowlege of dive theory is better served by a computer than they are with just a gauge...

But, I'm going to go with everyone here and say keep reading. It is no coincidence that almost every issue of every dive magazine has SOMETHING about deco in it. Seems to me that it is still rapidly evolving.

 

[kalvyn]

The deeper stops, and/or a long stop at 15-20 feet would be needed to get back into the Green zone strongly suggested. I was referencing this in the second part of my orginal post.

Which gets back to one of the points I made... did the diver plan the dive with enough gas to stop in the shallows until the computer is back into the Green zone? In my real-world example from Bonaire, no they did not.

I'm not trying to criticize anyone here, really. I'm just trying to make the point that we all need to think, and to be better educated on what that computer's doing (or NOT doing) for you. That's the point you were making in your original post too, Don, I was just trying to come from another angle to make the same point, really.

Jimmie