uwxplorer
Contributor
Take a 6 ft long piece of tubing, seal one end with a transparent window, fill it with water, set your computer to OC pure O2, dunk it in the tube with display facing down, and voila!
Thoughts on a new computer function
- Thread starter boulderjohn
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atdotde
Contributor
Fun fact: Several years ago, it was a bug in some dive computer (IIRC an early incarnation of Aladin nitrox computers) that did exactly that: They forgot to switch back to air while on the surface and computed the off gassing with the nitrox mix you were breathing through the dive. That of course let in general to too aggressive repetitive diving profiles and was soon fixed.
My guess would be that the altitude thing suffers the same problem as the no fly time: It is pretty ill defined and is not computed with the same model assumptions as the dive as otherwise the no fly times would be radically shorter (it would be hard, according to the Bühlmann with GF model to get much more than say 90min of no fly time even taking loss of cabin pressure into account. But recommendations are more like 12-24 hours. Those of course factor in that once in a plane at altitude it can be more difficult to get to proper treatment compared to while on the ground).
If you wanted, you could compute this in Subsurface: Plan the dive as usual (or read it out from your dive computer) then "Edit in planner", change the surface pressure to the altitude level you are worried about (the pass you want to drive over) and manually add a long stop at a very shallow depth where the depth corresponds to the pressure difference between on the shore and at altitude
My guess would be that the altitude thing suffers the same problem as the no fly time: It is pretty ill defined and is not computed with the same model assumptions as the dive as otherwise the no fly times would be radically shorter (it would be hard, according to the Bühlmann with GF model to get much more than say 90min of no fly time even taking loss of cabin pressure into account. But recommendations are more like 12-24 hours. Those of course factor in that once in a plane at altitude it can be more difficult to get to proper treatment compared to while on the ground).
If you wanted, you could compute this in Subsurface: Plan the dive as usual (or read it out from your dive computer) then "Edit in planner", change the surface pressure to the altitude level you are worried about (the pass you want to drive over) and manually add a long stop at a very shallow depth where the depth corresponds to the pressure difference between on the shore and at altitude
I don’t believe it would lead to more issues. As it currently stands, if you deco out on O2 then the computer switches to air for calculations on the surface but the selected gas remains. My Perdix will stay on the last gas selected so it is still an important step to select the correct gases afterwards.
My Poseidon M28 will surface deco on air BUT if I then switch to 100% it will continue to calculate on that gas.
The Cochran computers allow surface gas selection along with a genuine time to elevation counter. That’s to accommodate military divers who may need to fly somewhere shortly after dives but will suit for our purpose as well.
My Poseidon M28 will surface deco on air BUT if I then switch to 100% it will continue to calculate on that gas.
The Cochran computers allow surface gas selection along with a genuine time to elevation counter. That’s to accommodate military divers who may need to fly somewhere shortly after dives but will suit for our purpose as well.
Is there any effect on total CNS o2 time by breathing 100% o2 on the surface? Would or could it shorten your repeditive dives not based on nitrogen but rather CNS o2 limits?
TrimixToo
Contributor
I wouldn't mind if it were a user-selectable option, but I wouldn't use it personally. I try to guard against opportunities for error that I think are not needed, and for me (not necessarily for anyone else) this falls into that category. I'll take the few minutes of extra deco on Dive 2 to limit the chances that I'll forget to switch the computer back to air when I get out of the water and have it recommend less deco than I need or trim the margins I want to have. Also, I would need to have air defined as an active gas for that dive, which I don't often have.
OP
You don't have air as an active gas now when the computer switches to it for surface mode. I am just suggesting that you be allowed to override that to indicate that you are breathing something other than air.
J-Vo
Contributor
The idea that someone is trained to do trimix cave diving, but can't be responsible with there surface interval is silly. The more information I have the safer I am. I would rather make an educated guess than a just a guess. If someone is going to do something without proper training, they will do it with or without a fancy PDC feature.
J-Vo
Contributor
Maybe the solution is for it to default to air on the surface and you have to manually select a "surface" gas that is fully independent of your dive gas?
It could display a big red warning sign whenever anything but 21% is selected in surface mode.
It could display a big red warning sign whenever anything but 21% is selected in surface mode.
I like this idea and have occasionally wished for this feature.
I think it would be handy even for NDL diving, just to facilitate breathing a richer mix on the surface between NDL dives, in order to have a longer NDL on the 2nd dive.
I think it would be handy even for NDL diving, just to facilitate breathing a richer mix on the surface between NDL dives, in order to have a longer NDL on the 2nd dive.
As @RainPilot mentioned, Cochran found this an idea worth implementing. If enough of us request it, perhaps the other technical dive computer manufacturers will roll it out as a feature as well (ideally without needing a laptop).
It's a rare scenario where I personally would use the feature. I do have dive buddies who stay on a ccr loop while in dry passages sump diving caves, that sounds an ideal scenario for using this feature along with the other situations already described up thread.
It's a tool I would enjoy having available if my dive plan or contingencies require it. I like control.
Cameron
It's a rare scenario where I personally would use the feature. I do have dive buddies who stay on a ccr loop while in dry passages sump diving caves, that sounds an ideal scenario for using this feature along with the other situations already described up thread.
It's a tool I would enjoy having available if my dive plan or contingencies require it. I like control.
Cameron
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