Teric and Nitrox diving - Rec divers take care re method of changing gas (affects MOD).

[stuartv]

F/W version 11? Shame on you!

Yeah, yeah. I have been reading the Release Notes and waiting for a change that I thought I would actually benefit from. I don't like to risk breaking computers by upgrading firmware for no known good reason.

But, I am updating my first one to v16 right now...

 

[Jay]

If I'm understanding the situation, it sounds like FW16 works the way it should. If I'm breathing air and I do a gas switch to EAN32, I would be doing that because I'm using EAN32 as a deco gas. In which case, it should apply the Deco MOD.

The way it works on my Terics is really not the way I think it should work.

Yes, as SW said to me in my OP "You should only have gasses you are carrying and plan to use on the current dive turned on. Only one of these gasses are usually used on the working (bottom) part of the dive, the leanest mix. So that mix will use MOD PPO2 while all other mixes are assumed to be decompression gasses that will use the Deco PPO2 limit.".

FW16 seems to have been designed to rectify that for Deco diving, but for single tank Rec Nitrox divers the way we've been changing gases (inter dive) in the past (would seem) it didn't have a MOD consequence, now it does.

I must admit I'm still not certain if prior, or now, for all aspects of the dive (descent, bottom, ascent) for a given gas, is it a consistent PPO2 (either MOD or Deco) used (ref posts 2-5). I would assume it is but good points are raised above.

 

[Jay]

Yeah, yeah. I have been reading the Release Notes and waiting for a change that I thought I would actually benefit from. I don't like to risk breaking computers by upgrading firmware for no known good reason.

But, I am updating my first one to v16 right now...

Hey ... you can remove TTS now (at least on one Teric!!).

If you desire, you can re-run that test and compare. You're probably the only person who's got two of them on SB! (so far)

 

[stuartv]

I just finished the update on the 1st one and now the MOD3 (per my earlier post) is 133, instead of 112.

 

[Joneill]

Hey ... you can remove TTS now (at least on one Teric!!).

Exactly - I’ve been waiting since launch for that change and happy to have it now!

 

[Jay]

SW have responded and my OP is correct. They said "With v16, the Teric will use the OC DECO PPO2 limit to calculate the MOD on all phases of the dive for all decompression gasses. That is, all gasses that are not your leanest mix. So, in the example you give, your nitrox MOD will be calculated both on the surface and throughout your dive using the OC DECO PPO2 limit (default = 1.61). "

The example I gave was the same in this thread, that is, leaving Air On, and having Nitrox Active (achieved by using the (quicker) Select Gas menu).

SW did say they'll be working on things to improve the Teric for Rec divers.

Meanwhile, for my diving (Non-stop, single gas), I'm going to make OC Deco PPO2 = OC MOD PPO2. I can't see any issues doing that for my type of diving. [Edit - see post immediately below] Please do let me know if you think there's a potential pitfall of doing this. It's a 'work-around' and is merely to help with faster (inter dive) gas 'switches', and I know I'll probably forget do correctly switch the long way prior to next FW, (and it's nice to have the computer tell me if I should ever not pay attention to my depth).

 

[stuartv]

SW have responded and my OP is correct. They said "With v16, the Teric will use the OC DECO PPO2 limit to calculate the MOD on all phases of the dive for all decompression gasses. That is, all gasses that are not your leanest mix. So, in the example you give, your nitrox MOD will be calculated both on the surface and throughout your dive using the OC DECO PPO2 limit (default = 1.61). "

The example I gave was the same in this thread, that is, leaving Air On, and having Nitrox Active (achieved by using the (quicker) Select Gas menu).

SW did say they'll be working on things to improve the Teric for Rec divers.

Meanwhile, for my diving (Non-stop, single gas), I'm going to make OC Deco PPO2 = OC MOD PPO2. I can't see any issues doing that for my type of diving. Please do let me know if you think there's a potential pitfall of doing this. It's a 'work-around' and is merely to help with faster (inter dive) gas 'switches', and I know I'll probably forget do correctly switch the long way prior to next FW, (and it's nice to have the computer tell me if I should ever not pay attention to my depth).

If you are diving on Air, but you have told your computer that you are also carrying EAN32, the calculated TTS and (I think) the NDL will be wrong. I think you don't care about seeing your TTS, but obviously you do care about your NDL.

If the computer thinks you are carrying EAN32, then it's going to assume you are going to switch to it during your ascent. So, when it calculates what your tissue loading will be when you arrive at the surface, it's going to think you'll have less inert gas than what you really will. Thus, I think it will give you a longer NDL than it should.

If you are diving with Air and EAN32 off, and then doing a second dive with EAN32 and leaving Air turned on, I can't see a problem, off the top of my head (as far as resulting incorrect calculations), but it's still a bad habit.

Bottom line: Use your computer correctly. Don't tell it that you are carrying gases that you are not carrying. Going through the menus "the long way" to turn one gas on and another one off just isn't that time-consuming. Especially on a Teric.

If you do that, then you will have no reason to change the ppO2 limit settings.

If changing the computer "the long way" is too tedious, then just dive Nitrox all the time...

 

[Jay]

If you are diving on Air, but you have told your computer that you are also carrying EAN32, the calculated TTS and (I think) the NDL will be wrong. I think you don't care about seeing your TTS, but obviously you do care about your NDL.

If the computer thinks you are carrying EAN32, then it's going to assume you are going to switch to it during your ascent. So, when it calculates what your tissue loading will be when you arrive at the surface, it's going to think you'll have less inert gas than what you really will. Thus, I think it will give you a longer NDL than it should.

If you are diving with Air and EAN32 off, and then doing a second dive with EAN32 and leaving Air turned on, I can't see a problem, off the top of my head (as far as resulting incorrect calculations), but it's still a bad habit.

Bottom line: Use your computer correctly. Don't tell it that you are carrying gases that you are not carrying. Going through the menus "the long way" to turn one gas on and another one off just isn't that time-consuming. Especially on a Teric.

If you do that, then you will have no reason to change the ppO2 limit settings.

If changing the computer "the long way" is too tedious, then just dive Nitrox all the time...

Ohhh good point - Thanks!!!. Okies, yes, for sure good words to heed, "use your computer correctly".

 

[Jay]

A question for Perdix owners: is it possible to incorrectly use the Select Gas menu on the Perdix as one could do on the Teric? (or put a long way, If a Nitrox Rec diver had Air and Nitrox both listed with Air Active and Nitrox Off, and then selected Nitrox from the Select Gas menu, would that leave Air on?).

I'm suspecting it would work the same way but want to check.

 

[rongoodman]

I have Air and Nitrox in the gas list on my Perdix in Rec mode. Switching from one to the other in the Select Gas menu always displays the appropriate MOD. I was surprised to find out that it doesn't work that way on the Teric.