Quickest way to change gas on Perdix AI?

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hazmat

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What's the quickest way to change gas? For example, I'm on a dive trip and using Nitrox. Every tank could be a little different, so one might be 31%, the next 32%, etc. What's the best way to just go increment the gas by 1% or 2%?

Thanks.
 
You could set up a bunch of gases (say 31-36%) and just activate which ever one you are using in the gas switch menu. Although I wouldn't recommend diving with active gases that you aren't actually diving with.
 
You could set up a bunch of gases (say 31-36%) and just activate which ever one you are using in the gas switch menu. Although I wouldn't recommend diving with active gases that you aren't actually diving with.
What he said. Although, in recreational mode, the only effect having multiple gases turned on is when using the NDL planner (it will always use the optimal gas)

Honestly, though, if I analyse gases between 31 and 32 %, thats all well within the accuracy of the instrument / user error anyway. I don't feel that for NDL diving, having the computer set to 32 and diving 31 will make any real difference. I generally set 31 and use that for everything from 31 to around 33. Obviously if you are planning to dive right to MOD or expecting very big CNS exposures, take the time to set the correct gas but that IME is a vanishingly small percentage of most rec diving.
 
Dive Setup - Define Gas
You can also go through System Setup, but I think the Define Gas method is the fastest. Since I only dive single tank, NDL recreation dives I predefine Air EAN32 and EAN36 in System Setup then I can tweak them in Define Gas. I only turn on one gas at a time. If you leave multiple gases turned on, the computer will want to change gases in some circumstances.

Cheers - M² :scubadiver:
 
You can define multiple gas, but don't turn them all ON unless you're really diving with those gases, or the computer will assume that all those gases are with you during the dive, and it will ask you to switch to the optimal gas.
You can just adjust the O2 in the gas definition menu of the current gas, It's a matter of seconds, u can do it right before the dive(s).
 
I set it for 32% and leave it alone unless there's a significant change, e.g., when they blend a weaker mix for a specialty dive such as the Blue Hole off Belize. The mix always comes in between 31% and 33% on the LOBs I've been on.
 
pick the range that you have most common, for most divers it's typically 31-33%, set the computer for 31, and call it a day. Unless you are diving those gases where the ppO2 is 1.6, the EAD is not going to be that different for NDL's.
You said +2% and mentioned 31 and 32. So from 29-34

MOD is the most important thing to abide by here, and at 1.4, the MODs are below. You obviously have to be very careful when venturing below 100ft on Nitrox for what gas mix you're getting due to oxtox risk.
EAN29-126
EAN30-121
EAN31-116
EAN32-111
EAN33-107
EAN34-103

For NDL purposes, you need to be cognizant of EAD since that is essentially what the computer is tracking and is the benefit you get in NDL's while on Nitrox. Let's assume a 110ft/33m dive because it makes the math easy for me. The EADs are below. As you can see we have less than a 10ft range across the entirety of the mixes which is not going to equate to any real change in the NDL's. Heck, even on the NAUI dive tables, the difference in that dive is only going to be 3 minutes of NDL time if you are following it strictly. The difference between actual depth and EAD is obviously even less as you get shallower.
EAN29-94
EAN30-93
EAN31-91
EAN32-89
EAN33-87
EAN34-86

For what to really do? If you are regularly getting mixes in the 30-33% range, and are not at risk of violating the MOD's of any of the mixes, just set the computer to EAN30 and be done with it. No need to change gases in the computer for 1-2% in your mix. On 50/70 which is what I dive, Decoplanner says 14mins at 108ft on EAN29 is NDL, 16mins on EAN32, and I get 17mins on EAN34. Hardly worth the effort in my opinion to change gases for a minute here of there. If you are running more aggressive GF settings, then it will spread out a bit more, but not by more than a few minutes. To me that isn't worth the hassle of changing gases, and running a bit more conservative never hurt anyone.
 
pick the range that you have most common, for most divers it's typically 31-33%, set the computer for 31, and call it a day.
<snip>
For what to really do? If you are regularly getting mixes in the 30-33% range, and are not at risk of violating the MOD's of any of the mixes, just set the computer to EAN30 and be done with it. No need to change gases in the computer for 1-2% in your mix.
<snip>
To me that isn't worth the hassle of changing gases, and running a bit more conservative never hurt anyone.
^^^What he said^^^
My computer is usually left on 30, and I stay above 100 ft. I'm good with that to 34%, which I've never had from a resort/diveboat that supplies "32%". But I always check the percentage....
 
You could set up a bunch of gases (say 31-36%) and just activate which ever one you are using in the gas switch menu. Although I wouldn't recommend diving with active gases that you aren't actually diving with.
Doesn't rec mode only let you set up a max of three gases?
 
Thanks, all. This is really helpful. I'm fairly new to the Perdix, mostly used to my old Oceanic Atom. So far I've only used the Perdix with Air, so changing Nitrox values hasn't come up yet. Interesting to me is about just leaving the O2% at one value for differing actual readings of about +/-1%, but it makes sense with respect to MOD. In this case it's just for rec diving in Cozumel.
 

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