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I dove at Paradise Springs today, I dove a single tank with a AI computer and my NITEK 3. It was a nice dive I used 1/2 of the 120cf of 21% during the 52 min dive with 14 min at 99ft.
My dive profile was slow down to 99ft 14 min there, then began working my way back up spent 5 min at 15ft before exiting. Both my computers showed I stayed in the no Deco limits, and I knew before getting wet that my absoulte bottom time was 20 Min @100ft.
When I was on my SI, I tryed to figure out what my pressure group was and well, I couldn't. So my question is how do I figure this? I know my profile was acceptable and I based my SI on past experances, and watching my computers off gas.
Is there a correct way to calculate my pressure group or am I out of luck once I exceed the published PADI tables? What am I missing here?
Is this something that would be covered using software such as V-planner, and then I just ignore the pressure group for repetitive dives?
It's pretty much impossible to figure out a pressure group based on what you did on a multi level dive with a computer... but you can sorta' wing it after the fact.
What you can do is start dive planning as soon as you come up. Let's suppose you check your computer and it says that after that dive, if you want to do a 60 ft dive now, you can only stay down 10 minutes... Well, then just turn to your tables and figure out what group would put you there... That would make you about an R on a Padi table.
Depending on which computers you are using, this may or may not be all that accurate, and I'd tell you don't worry about putting in a pressure group in your log as it's going to be a guess after a multi level profile - unless you call it a big square profile, in which case... head directly to chamber. But if you want to put a letter group in there... this seems to be the closest way to come up with one that is pretty close.
Thanks, I searched the threads and seen some usable advice on older threads. I never considered it before but was diving with a new buddy who is a new diver and he ask questions of the SI time so I went to my charts and relized I never have addressed this before because I use multiple computers and at least 1-1.5 SI every time.
If you get "The Wheel" you can back into a pressure group if you have a close estimate of the times you spent at different depths. It won't be perfect, but you'll be pretty close then you can drop down another PG for safety.
Go to your Nitek 3 and read the profile mode setting of your dive. It will tell you what time you actually spent at 100 feet. The tables are based on the time you descended and the time you actually spent at depth aka Bottom time. Your computer (s) provides your actual dive information and gives credit for the ascent (running time). You can base your PG from the time you actually spent at depth (computer in profile mode) as tables donot account for the time of ascent with any accuracy. The Wheel can provide you a comparison of table to computer read outs.