Diving Nitrox with Computers?

[driebel]

Hey, Dave, <snip>

the information on your wrist really is giving your brain the needed input.
The Vyper does have a "max. depth alarm" that you could select ( in the place of a MOD display) ; that would replace the process. Hope this helps..

Hey CardShark,

Thanks for the reply. I agree, a manual setting of the maxdepth alarm seems to be the closest thing. This first part of your reply I quoted is close to the real meat of my question. I guess I still feel that ((1.4/(EANx%))-1)/10 is a more useful quantity than just the EANx% by itself. Didn't we invent computers to avoid doing mental math?

 

[scubadiver888]

driebel,

The MOD is important but is it important it is displayed on the computer? If I am designing the software for a computer and I have limited display space, I would drop the MOD from the display because the user (you) doesn't need to have the MOD on the computer display. They can write the MOD on a slate, their hand, whatever. Because it does not change during the dive, there is no need to place it on the dynamic display of the computer.

If I was buying a computer, one computer displayed the MOD but not the O2 clock and the other displayed the O2 clock but not the MOD, I'd buy the second computer because I can always write the MOD on my hand (or just remember it during the dive). My MOD is written on my tank after I analyze the contents. When I'm setting up my gear, I can see my MOD before I put it on. Not hard for me to remember it throughout the dive.

 

[Tool Belt]

Also, remember to use the computer's PO2 information when figuring your 24hr O2 exposure (assuming multiple dives within that period).

 

[AzAtty]

So you mean: why did Suunto choose to display the O2 percentage instead of MOD? I don't know, other than MOD at 1.2 is different that MOD at 1.6, and Suunto didn't want to get preachy about which which number to use. The Vyper platform has been around a long time. Back years ago, 1.6 was sometimes acceptable (NOAA has been consistent with its recommendations, but some guys ran pretty hot mixes during the working portion of the dive). As Nitrox lost its "voodoo gas" status and moved mainstream, the current PPO2 came to the generally acceptable, present levels. That's based both on better data, and also the need to add a safety margin for the weekend warriors.

 

[DevonDiver]

As your personal decision of allowable ppO2 at a given level of exertion is what you need to base your judgement of MOD on, .

Without getting in a semantic debate about personal freedom... I don't think any agency teaches a flexible system of ppo2.

If the OP learnt with PADI, then his max ppo2 for planning purposes is 1.4

Having a 'personal opinion' on allowable ppo2 requires knowledge and experience that far exceeds anything taught on a recreational level course.

Just saying....

The MOD is important but is it important it is displayed on the computer?

It shows the MOD when you program in the O2%. But it isnt displayed on the dive.

Dsiplaying the MOD during the dive is only important if the diver concerned had a mental impairment that heavily degraded their short-term memory.

How hard is it to remember an MOD for the duration of a scuba dive?

("my MOD is 90'.....my MOD is 90'......my MOD is 90'.....my MOD is 90'.....my MOD is...errr...ummm... oh bugger!")

...and then, of course, you will have included your MOD within the dive planning and briefing... so your buddy will be consiously and diligently supervising that also....

So, having the MOD on your computer screen would only really be critical for divers with the memory recall of a goldfish.... who chose to dive with an equally mentally deficient buddy.

Even then.... you could still write the number on your hand...

That's based both on better data, and also the need to add a safety margin for the weekend warriors.

Wheras us 'hardened nitrox warriors' don't need those safety margins, because we are tougher and more likely to shrug off the effects of an O2 hit??

 

[syntaxerrorsix]

Without getting in a semantic debate about personal freedom... I don't think any agency teaches a flexible system of ppo2.

If the OP learnt with PADI, then his max ppo2 for planning purposes is 1.4

Having a 'personal opinion' on allowable ppo2 requires knowledge and experience that far exceeds anything taught on a recreational level course.

Just saying....




Only if the diver concerned had a mental impairment that heavily degraded their short-term memory.

How hard is it to remember an MOD for the duration of a scuba dive?

("my MOD is 90'.....my MOD is 90'......my MOD is 90'.....my MOD is 90'.....my MOD is...errr...ummm... oh bugger!")

...and then, of course, you will have included your MOD within the dive planning and briefing... so your buddy will be consiously and diligently supervising that also....

So, having the MOD on your computer screen would only really be critical for divers with the memory recall of a goldfish.... who chose to dive with an equally mentally deficient buddy.

Even then.... you could still write the number on your hand...

NAUI teaches that you can build in conservatism by diving a lower pO2.

They even have an example of a diver doing that very thing in the section covering Oxygen Percentages for Best Mix. The scale is from 1.2 to 1.6

Page 47.

Beyond a 1.6 I fully concur.

 

[DevonDiver]

Yep.... that's why it is called a max PPO2

 

[syntaxerrorsix]

Yep.... that's why it is called a max PPO2

Without arguing semantics "max" does not mean "only" :mooner:

 

[DevonDiver]

Thanks for the english lesson. I wasn't aware that anyone had stated that 'max meant only'.

What had been said was that divers could make a "personal decision on allowable ppo2". That, to me, seems like a very different statement to making a "personal decision on conservatism within recommended ppo2 limits".

Other than randomly adding conservatism...exactly how is a recreational diver educated to calculate a personal max ppo2?

 

[driebel]

driebel,

If I am designing the software for a computer and I have limited display space, I would drop the MOD from the display because the user (you) doesn't need to have the MOD on the computer display. They can write the MOD on a slate, their hand, whatever. Because it does not change during the dive, there is no need to place it on the dynamic display of the computer.

If I was buying a computer, one computer displayed the MOD but not the O2 clock and the other displayed the O2 clock but not the MOD. <snip>

If you are flying your computer instead of the plan you aren't playing by the rules taught in your OW class or Nitrox Course.

To me a computer isn't really a reminder of a plan, but real time tracking of the situation against a plan that should be in your head.

Nice. Several people have given good opinions on this, thanks for that. I agree with the importance of the O2 clock stated above, but I'd point out that Suunto didn't debate between a static MOD and a dynamic O2 clock, they debated between a static MOD (37m) and a static O2 percentage (29%). As it stands, one of the largest numbers on the display is a giant 29% throughout the dive. With which I can do...? (easily)

For the record, to this point, I am PADI born and bred, and an MOD based on a ppO2 of 1.4 is an iron law in my head that shall not be violated, or even really approached for that matter. Until I've taken several other courses, I'm perfectly content with that for the moment.

I'm enjoying the discussion of those more educated than I, and appreciate having the reasoning spelled out. I see jmasin's point in particular, but respectfully still think a linear transform of the mix percentage is more useful than the percentage directly.