Vytec Nitrox PP O2 question

[Henry]

I have yet to figure this out and have read the manual several times. I am hoping someone can explain this to me.

When entering the mix for my nitrox (say 33%), the Vytex allows me to alter the pp O2 from 0.5 to 1.6. When I press the up and down buttons to do so, it changes the max depth.

Up to now, I have just left it at 1.4. But I am curious, what is the point of this?

For example, I dove today with 33% nitrox. The pp O2 is 1.4 at 102 feet. If I changed it to 1.5, it goes to 112 feet. Is it an alarm setting?

Thanks for helping out.
Henry

 

[grazie42]

The point is that, for example while doing deco, you might feel it acceptable with a higher ppo2 like 1.5 or 1.6. Obviously changing that setting makes it possible to change mix on the comp earlier/deeper. It simply wont allow you to switch earlier than the max depth for whatever mod you´ve selected and also increasing ppo2 let´s you go deeper on the same mix without it complaining...

As I´m sure you know the recommended working pp02 is 1.4 and dont exceed the limits of your training,[insert disclaimers of your choice here] and so on.

Hope this helps...

 

[Henry]

The point is that, for example while doing deco, you might feel it acceptable with a higher ppo2 like 1.5 or 1.6. Obviously changing that setting makes it possible to change mix on the comp earlier/deeper. It simply wont allow you to switch earlier than the max depth for whatever mod you´ve selected and also increasing ppo2 let´s you go deeper on the same mix without it complaining...

As I´m sure you know the recommended working pp02 is 1.4 and dont exceed the limits of your training,[insert disclaimers of your choice here] and so on.

Hope this helps...

Yes I was aware that Vytex will not allow me to change to a mix that is not appropriate for my depth (ie. 100% O2 at 80 feet). So the abilty to change the pp O2 in my question only effects when I can do gas switching?

In my example if I am set for 33%, 1.4pp O2, 102 feet. I can't switch to this mix until 102 feet or shallower. But If I entered my mix as 33%, 1.6 pp O2, 122 feet. I can switch to this mix as earlier as 122 feet?

Is this all it does?

Thanks
Henry

 

[sharkbaitDAN]

By setting the PPO2 to a higher number, 1.4 to 1.6, you will have the computer yelling at you a little later. All of the Suunto Nitrox capable computers have the same function. For the rest, it beeps and flashes that you are too deep on a given mix. I found the Suunto calculation to be slightly off (too shallow) of mine, so I set the PPO2 to the depth that I want, and am careful not to go deeper. I think it was put there largely for wall dives and blue water dives, where divers can find themselves way too deep if they're not paying attention.

 

[miketsp]

Henry,
I am not sure if you are getting the message. The 1.4 is a safety limit (recommended by most agencies). If you raise it you are not just choosing an arbitrary number, you are increasing your risk. If you lower it you are increasing your safety margin.
You must be clear on this.

Mike.

 

[Henry]

Henry,
I am not sure if you are getting the message. The 1.4 is a safety limit (recommended by most agencies). If you raise it you are not just choosing an arbitrary number, you are increasing your risk. If you lower it you are increasing your safety margin.
You must be clear on this.

Mike.

Mike,

I know what 1.4 is. Please read my original question. I am trying to find out why Vytec allows me to enter pp O2 value between 0.5 and 1.6.

Also the Suunto fsw is shallower then my calculations. In my example, 1.4 pp O2 for 33% is only 102 feet instead of 107 feet. Hence the question for adjusting the pp O2.

I am not asking if 1.4 pp O2 or higher is dangerous for me.

Henry

 

[miketsp]

Mike,

I know what 1.4 is. Please read my original question. I am trying to find out why Vytec allows me to enter pp O2 value between 0.5 and 1.6.

Also the Suunto fsw is shallower then my calculations. In my example, 1.4 pp O2 for 33% is only 102 feet instead of 107 feet. Hence the question for adjusting the pp O2.

I am not asking if 1.4 pp O2 or higher is dangerous for me.

Henry

Ok, fine, that makes me happier. It's just that I didn't see anybody actually saying this in the replies.

As for 102ft against 107ft, the salinity of salt water varies somewhat within the oceans and can be much higher in some inland seas. I suppose a worst case would be the Dead Sea. Higher salinity would give less than 33ft per ATM so Suunto are probably playing safe.

 

[Soggy]

Also the Suunto fsw is shallower then my calculations. In my example, 1.4 pp O2 for 33% is only 102 feet instead of 107 feet. Hence the question for adjusting the pp O2.

Yeah, Suunto somehow forgot how to do basic math. If you dive it in Gauge mode, you can avoid the whole problem. Or, alternatively, you could raise it .1 over what you actually want. I keep mine set at 1.5, but never exceed a "real" 1.4.

 

[rab]

Just doin' the math, it looks like 34% and ppO2 of 1.4 has MOD of 102ft. Is this consistent? I.e., Suunto actually gives the MOD of the next higher O2 mix? Henry's example of 33% 1.6ppO2 of 122ft (rather than 127ft) seems to agree with this, 34% 1.6 ppO2 is 122ft. (It might also always take off 5ft...)

-Rob

 

[Henry]

Ok,

I phoned Suunto and they give me this answer:

The reason the pp O2 is adjustable is because Suunto realizes that different agencies teaches different things. Such as PADI teaches 1.4 ppO2 is the the max depth but NAUI teaches 1.5 is the max depth. Suunto lets you play with the ranges from 0.5 to 1.6 to let you have some flexibility.

The only thing it does is changes the depth at which the alarm will go off.

But the fsw is burn in to the circuit board and can't changed. In my example, the 102fsw, 33%nitrox, 1.4pp O2. The 102 is a fixed number in relation to the 1.4. If you wish to increase the fsw, you would haev to change the pp O2 to 1.5 which would give you 112 fsw.

The fsw calculation is about 5 feet shy of the real value (my Vytec is set at 50% RBGM) due to built in conservatism.

Hope this helps
Henry