NITROX computer questions

[DiveNav]

This is a Pelagic-type computer, right? .

Correct

 

[Graeme Tolton]

Read the manual for your computer. If you have already read it, read it again! If you don't have it, go to the manufacturer for it. This is an important safety feature, designed to protect you. In the event that you forget to set the Fo2, it will revert to more conservative tables...

 

[theduckguru]

is it a sherwood insight or wisdom?

it sounds like mine.

the o2 setting going back to 50% after a dive is a safety.

if you forget to reset your FO2 for the next dive, it will calculate a hypothetical gas of 50% O2 and 79% N2, a worst case scenario. you will be penalize in time and depth, but at least you'll be safe.

As for the 10 minutes-waiting, it is because if you get back in the water before 10 minutes, the computer will consider it the same dive, so no need to change the FO2.


with the FO2 setting at ON, if you set your computer for Nitrox 21%, it will stay at 21% between dive, but it will be "stuck" in nitrox mode" untill it shut down 24h after the end of last dive.


You should re-read the manuel to know exactly what your computer tells you.

I can understand the 79% safety margin, but 50% O2 - where did they get that figure? Sounds like you would get a really shallow MOD with a very long NDL.

 

[Graeme Tolton]

Most computers will use a theoretical mix of 50% o2 and 79% nitrogen. This will provide safety for both gasses, because YOU forgot to enter Fo2. The Nitrogen tables will be based on air, but O2 tracking, MOD will be based on 50%

 

[Marek K]

I can understand the 79% safety margin, but 50% O2 - where did they get that figure? Sounds like you would get a really shallow MOD with a very long NDL.

Should be a really shallow MOD (based on the 50% O2 assumption) and relatively short NDL (based on the 79% N2 assumption). And correspondingly long surface interval required afterwards. In other words, extremely conservative and safe.

Your punishment for forgetting to set the PO2.

 

[highdesert]

If it's an Oceanic, you can override that feature one time and it stays like that until you choose to reset it ... just do it. I disable it every time I put in a new battery, and I'm good to go for a year.

PS - I hate Oceanic manuals ... they're the scuba equivalent of a software engineer writing a casual user's manual for a computer program.

 

[scubadada]

I've been diving Oceanic computers (Pelagic Pressure Systems) for more than a decade. Turn the FO2 50% Default to OFF and check and set your actual FO2 before each dive.

I find the Oceanic computers intuitively easy to operate and have always found the owner's manuals clear and concise whenever I've had a question.

Good diving, Craig

 

[Marek K]

I find the Oceanic computers intuitively easy to operate and have always found the owner's manuals clear and concise whenever I've had a question.

I agree that their manuals are good if you have a specific question about a function. Not so good in general describing or teaching how the computer operates.

With four divers in the family, we've got two Oceanic Veo 180's and two Aeris Atmos 2's. Fortunately the displays and operation are analogous, and the manuals are very similar. But the two-button vs. one-button operation makes it a bit hard for us to help each other out with an issue of how a particular function is accessed.

 

[Garth]

I don't really see why people buy these computers. They seem like a pain in the a$$.

 

[Blackwood]

I can understand the 79% safety margin, but 50% O2 - where did they get that figure? Sounds like you would get a really shallow MOD with a very long NDL.

As Marek noted, you don't get "a very long NDL." You get an air NDL, and are 'held' to the depth which corresponds to whatever the max PO2 you set assuming EAN50, and you rack up CNS (and OTU if your computer counts that).

As to where they get it (i.e. 50%, as opposed to 40% or 80% or 100%), I have no idea. It's arbitrary. They probably took the richest "basic nitrox" blend and added 10% more.