Diving Nitrox with Computers?

[DevonDiver]

Back to the OP:

The following pic illustrates the set-up for vyper in nitrox mode. Having entered the O2%, it will display the MOD (top left). This should be committed to your (not the computers) memory for the duration of the dive. The PPo2 (in this case 1.4) can be manually adjusted within the settings.

 

[driebel]

Hi DevonDiver,

Thanks for introducing a photo into the discussion, should have done that myself. Unfortunately, I can't view it for some reason. Based on your description, it sounds like the planning mode of the Vyper (maybe figure 3.20 from the manual?) I've attached figure 3.22, which shows the screen while diving. Notice the big central number 32, which is not ppO2 (obviously!), but just O2 percentage. It's simply a handy reminder of what's in your tank. Constantly.

I fully agree that best practice is just to know your plan and dive your plan. The question is, why is that 32% a more useful static parameter to stare at during the dive than 32.8m, the MOD for a 1.4 ppO2? Let's fix the discussion at 1.4 ppO2, for simplicity. We all know we can choose to plan dives for other ppO2s, that's not the point. Obviously, I think the MOD displayed should be the MOD for your chosen ppO2. It seems to me, if you're going to take up screen space during the dive with a static number, why go with percentage O2? Why is that better than MOD? Is it? In my opinion, that space would be better filled with 32.8m instead of 32%. Is there a clear argument in favor of 32% instead? What are the drawbacks to putting 32.8m there instead of 32%?

 

[Blackwood]

One thing I find intersting is that the OP is asking specifically about computers for nitrox dives.


Why not all dives? Is MOD A.) unimportant for air, B.) easier to remember than for nitrox, or C.) is it deeper that you'll go?

If C., why is it easy to remember how deep you'll go from a deco-table standpoint but not easy to remember how deep you go from a PO2 standpoint?

Seems strange.

Plan your dive including a "this is as deep as I'll go" parameter. Regardless of whether it's most severely limited by deco, gas supply, gas contents, etc., remember the most severe limit.

[/confused]

 

[Blackwood]

Why is that better than MOD? Is it? In my opinion, that space would be better filled with 32.8m instead of 32%. Is there a clear argument in favor of 32% instead? What are the drawbacks to putting 32.8m there instead of 32%?

I suppose there are a number of considerations.

Maybe an MOD display is helpful during regular dive operations. What about failure handling?

If the unit crapped out and you bail to tables, would you rather have been staring at MOD the whole dive and working backwards to figure your mix, or would you rather have been staring at the mix the whole dive?

 

[fire_diver]

Yep. They didn't go into design philosophy such as "Why we feel this information is more useful than other information."

C'mon, man. The description of this forum specifically states: "This forum has special rules. This forum is intended to be a very friendly, "flame free zone" where divers of any skill level may ask questions about basic scuba topics without fear of being accosted." (Emphasis added)

My question doesn't come close to "I'm dumb and can't use my computer." It's a question about the usefulness of certain information to maximizing safety and making things idiot-proof. I have an opinion of what information is more useful in certain situations, and I wonder why others (the designers) feel other information is more useful.

Your snark isn't helpful.

You might want to change your underwear, yours seem to be a little tight at the moment if you thought my question was some sort of insult against you. It was an honest question. There is an endless parade of people who come through every type of forum asking questions that are clearly explained in the users manual.

You answered the question. Others have since given you good ideas on the reasons for the displays, so not much to add there. As for your treating MOD as some sort of land-mine filled demilitarized zone that will kill you for even looking at it, you need to go back and have a talk with your instructor or maybe other instructors.

 

[fire_diver]

One thing I find intersting is that the OP is asking specifically about computers for nitrox dives.


Why not all dives? Is MOD A.) unimportant for air, B.) easier to remember than for nitrox, or C.) is it deeper that you'll go?

If C., why is it easy to remember how deep you'll go from a deco-table standpoint but not easy to remember how deep you go from a PO2 standpoint?

Seems strange.

Plan your dive including a "this is as deep as I'll go" parameter. Regardless of whether it's most severely limited by deco, gas supply, gas contents, etc., remember the most severe limit.

[/confused]

MOD isn't important for air because you won't come close to it at any sort of recreational dive. If you are planning dives that might exceed 1.4 for EAN21 You have a lot more to worry about than the toxicity of the oxygen component.

 

[syntaxerrorsix]

MOD isn't important for air because you won't come close to it at any sort of recreational dive. If you are planning dives that might exceed 1.4 for EAN21 You have a lot more to worry about than the toxicity of the oxygen component.

MOD is always important because it is part of your plan.

 

[fire_diver]

MOD is always important because it is part of your plan.

If you are diving air to recreational depths, you will not come close to any tolerance threshold toxity. It can be ignored because you know you are not coming close to a MOD violation for CNS or pulmonary.

 

[syntaxerrorsix]

If you are diving air to recreational depths, you will not come close to any tolerance threshold toxity. It can be ignored because you know you are not coming close to a MOD violation for CNS or pulmonary.

You're missing/missed his point.

MOD is ALWAYS a part of the plan. Not just for nitrox diving.

 

[DevonDiver]

You're missing/missed his point.

MOD is ALWAYS a part of the plan. Not just for nitrox diving.

Max Depth is always part of the plan. But MOD (Max Operating Depth), a different term, specifically refers to the characteristics of a gas being used for diving.

For recreational divers using air, the MOD is so far below the recommended limits for diving that it would be fruitless to include that factor within a dive plan. I mean...come on... 185'... just for the sake of mentioning it?!?