Nitrox Computer Setting

[John_B]

I actually tend to set my computer to 31 and leave it there for a week of the usual scattering of tanks around 32 unless something is way off.

That was the other thing that I found annoying with the Vytec. Even though >95% of my dives are on 32% (-ish), it would always be resetting itself to 21% in nitrox mode. :11doh: I used to call it the "mother hen" feature. I don't fly a computer down to the NDL/no stop time anyway.

My Tec 2g lets me decide how to configure those settings.

 

[Charlie99]

That was the other thing that I found annoying with the Vytec. Even though >95% of my dives are on 32% (-ish), it would always be resetting itself to 21% in nitrox mode. :11doh: I used to call it the "mother hen" feature.

Just be glad you didn't have an ancient Oceanic hocky puck like my 1 button Data Plus. It defaults back to physically impossible 79% N2, 50% O2 if you don't set it before the next dive.

The more modern Oceanics let you turn off this "mother hen" feature.

 

[LowVizWiz]

That was the other thing that I found annoying with the Vytec. Even though >95% of my dives are on 32% (-ish), it would always be resetting itself to 21% in nitrox mode. :11doh: I used to call it the "mother hen" feature. I don't fly a computer down to the NDL/no stop time anyway.

My Tec 2g lets me decide how to configure those settings.

I think it does that because the manual recommends you leave the computer permanently in nitrox mode when diving air & nitrox. So instead of reseting itself to Air mode it just thinks you're diving EANx 21 DOH! kinda dumb.

Do you dive 32 all the time because it's just simpler or is there a different reason for it?
If I know I'm only doing 2 dives I like a higher mix on the second shallower dive.

Wys.

 

[Damselfish]

Yeah, I have Suunto's and that "feature" where they set back to 21 after some number of hours is pretty annoying. I can sort of see the conservative logic that led to that but it's still really annoying. If I'm on a liveaboard it usually doesn't have enough time to decide to reset itself, but land based where I might be out of the water longer it's always doing that.

Lots of people dive 32 most of the time simply because many places just pump 32% and even if they can or will do something else, it's more of a nuisance to get something else than it's worth.

 

[Eastbayfe]

Yeah, I have Suunto's and that "feature" where they set back to 21 after some number of hours is pretty annoying. I can sort of see the conservative logic that led to that but it's still really annoying.

On my last dive I paired up with a couple of "experienced" divers with hundreds of dives logged. Near the end of the dive one of them shows me their computer. It had reset before she jumped in and she hadn't caught it. She was gauging by mine and the other divers dive time. That was a bad position to put oneself in.

 

[LowVizWiz]

It resets after 2 hours of inactivity when really there's no need!

 

[don Francisco]

In Cozumel my wife's Chressi Archimedes used to reset the mix to 100% oxygen on a regular basis between the first and second dives. Even if she set it, just as as she was about to jump in she'd notice it had reset itself. It drove her nuts until we figured out the problem.

Our second dives typically started just after noon. The Archimedes has a feature in Nitrox mode that resets it to 100% Oxygen at midnight, so as to force you to check your setting each morning. You geussed it, she had set her clock in the 12 hour mode and was 12 hours off, having midnight and noon reversed. Once we solved that headache, she would always set the time in the 24 hour mode, then change back to the 12 hour display.

 

[John_B]

Do you dive 32 all the time because it's just simpler or is there a different reason for it?

Yes, standardizing on 32% simplifies a lot of things, provided both buddies are on the same page. Its very versatile.

You can really do almost any recreational dive with it. The MOD at pO2 of 1.4 is 111 feet and the contingency MOD for emergencies is still 132 feet. So down to about 100' or maybe 110', 32% is a no brainer. And the difference in N2 between 32% and air is still significant enough that the benefits are measurable when you are doing four or five dives a day, day after day. Or two deep dives a day, two days in a row. Or whatever.

As long as my dive buddy has the same training and thought processes I do, dive planning is straight forward. The NDL/MDL times for 32% are simple to memorize, and the EAD adjustment from air tables to 32% works out to be an even 20% -- that's math I can easily do in my head, even underwater.

From my experience, its also easy to get 32% fills. Most places that bank nitrox seem to at least bank 32%. It's also GUE's standard for nitrox; almost all of their standard trimix gasses can be mixed starting with a given pressure of pure helium, then topping with 32%. Why that matters at this level is that most GUE-friendly shops will have thousands of cu ft of 32% banked, ready for fills.

So, yes, I guess I could try to eke out a little more no-stop time with 36% or 40% or to save a little money with air fills. For me, the tradeoff isn't worth losing the flexibility that a standard gas gives to a team. It sounds strange that a standard for nitrox would give a team more flexibility, but it works out that way. Right now I have two AL80s sitting in my mudroom with 32% that were originally supposed to be for practice drills followed be a fun dive in a quarry with a friend, but instead they will probably be used for a pair of deeper lake dives.

As always, YMMV.

 

[Eastbayfe]

Off the coast here it is typical to be diving 118' feet at U-352 and deeper on some of the other wrecks so mixes of 30 percent and less is prefered to keep your MOD where you need it.

 

[John_B]

Off the coast here it is typical to be diving 118' feet at U-352 and deeper on some of the other wrecks so mixes of 30 percent and less is prefered to keep your MOD where you need it.

Exactly. Below about 100' I stop looking at the dive as a strictly recreational dive. That changes how I look at a number of factors:

• Team Skills/Buddy Reliability
• Leaner mix/MOD
• Rock Bottom/Redundancy
• Being narced at 4+ ATA