Residual Groups and Computers

[landlocked]

Just a quick question. When planning a repetitive dive, and diving with a computer, how do you account for residual nitrogen and thereby determine how long and how deep your next dive can safely be?

 

[mikelegurra]

if i understand the question, wouldn't it be easier to use the tables ??

 

[H2Andy]

your computer will tell you. it calculates the new max depth/max time for the next dive every minute of the surface interval and it displays that information for you.

mine, for example, will not do so for the first ten minutes of the surface interval, but then it will start showing me my max times at the diffrent depths, from 40 to 140 feet.

you can also learn how to calculate multi-level diving profiles by hand (with the wheel or such), but regular tables won't work for this.

 

[dutch-scuba-kid]

Yeah...
What's wrong with them?
I'm not sure I can even calculate something like that without the help of whatever you could use.

 

[H2Andy]

if i understand the question, wouldn't it be easier to use the tables ??

well, unless they are multi-level tables, they will not
give him the maximum dive times that a computer can
by virtue of calculating the multi-level nitrogen intake.

 

[mikelegurra]

well, unless they are multi-level tables, they will not
give him the maximum dive times that a computer can
by virtue of calculating the multi-level nitrogen intake.

that's why i thought i might be missing the point.
as you pointed out in your previous post, the computer already tells you what the allowed dive time is for the current depth, or using the planing function if you're above water.

 

[H2Andy]

ok i'm confused now...

happy?

 

[simbrooks]

So what do you do with those nice little PADI tables that let you put in pressure groups at the end of your dive in your log????

 

[rab]

Your dive computer might have a "PLAN" mode (as my Suunto Mosquito does) that lets you preview the NDL time at various depths as H2Andy said. As for backing up the computer with tables and/or Wheel, how closely did you follow your plan? If you planned to do multi-level (and dove it that way), you can work the Wheel to give your pressure group. You can use the PADI table for a multi-level dive by treating each part of the dive separately with a 0:00 surface interval. If you know the rules for the minimum depth change for the "multi-" parts, then the result between PADI's Wheel and RDP Table will be the same (perhaps the tables will show a bit more conservatism due to "rounding", but close enough). There is (at least) one difference that the Wheel makes plain and that's the reduced NDL times on multi-level dives so if you're taking the dive all the way to the NDL, you can get pretty far off of the computer. (Since as others have pointed out, it can track your actual profile, not just an approximation.)

-Rob

 

[scubafool]

Regarding Sim's post, I note tank pressure & NDL from the table at max depth (if I know what the depth is) on a slate before I get wet. I also wear a watch, so if something weird like forgetting to turn computer on were to happen, (hey I've only done it once) I'd have SOME idea where I stood.