Calculating total dive times for multiple depths

[sungod357]

Does this sound correct to anyone else?

Using air tables, we know that the amount of nitrogen absorbtion is multipied by the number of bar you dive.

33+ft (2 bar)= 2 x surface nitrogen
66+ft (3 bar) =3 x surface nitrogen
99+ft (4 bar)= 4 x surface nitrogen

So if

a dive to 100ft(4 bar) means you are absorbing 4 x the amount of nitrogen as the suface.

and a dive 50ft(2 bar) means you are absorbing 2 x the amount of nitrogen as the surface.

Then does it stand to reason that

If I multiply the time spent at lower depth by the multiple of the rate of nitrogen absorption (2,3,4 bar) at lower depth. I now have an equivalent nitrogen absorption time.

Dive to 100ft(4 bar)for 5 min, then accend to 50ft(2 bar) for ? minutes

5 min @ 100ft x 4 (bar) = 20 min @ 50ft(2 bar)

5 min x 4 bar =20 min @ 2 bar

Then I subtract that amount of time from the planned shallow dive time

50ft for 40min- 20min = 20 min left @50ft.

I have already included my safty stop by knock back the 50ft planned dive time from max to 40min.


just checking if that is right.

sungod

 

[Dive-aholic]

No. I think you're trying to figure out how to use the table as a wheel. You don't need to do any mathematical calculations. Plan your initial depth for the length of time you plan on spending there. Then plan your next depth as a 2nd dive with no surface interval. You will need to subtract the residual nitrogen from the NDL at the new depth to come up with your adjusted NDL. Don't forget air consumption. It can shorten your dive times.

Finally - 50ft is not 2 bar, 33ft is 2 bar (look at your own table). 50ft is 2.51 bar.

 

[TeddyDiver]

Does this sound correct to anyone else?

Using air tables, we know that the amount of nitrogen absorbtion is multipied by the number of bar you dive.

33+ft (2 bar)= 2 x surface nitrogen
66+ft (3 bar) =3 x surface nitrogen
99+ft (4 bar)= 4 x surface nitrogen

Nope! They are just multiplied partial pressures (PN2) of the inhaled air. The amount of nitrogen absorption comes when you take PN2air at depth-PN2 of the selected tissue and multiply it with the Time spend at certain depth/halftime of the tissue Then make same calculation with 15 other tissue types and vola! To get the calculation accurate enough take it again every minute...

 

[budgy]

Obviously most of us are never going to do those sums in our heads.

 

[sungod357]

Nope! They are just multiplied partial pressures (PN2) of the inhaled air. The amount of nitrogen absorption comes when you take PN2air at depth-PN2 of the selected tissue and multiply it with the Time spend at certain depth/halftime of the tissue Then make same calculation with 15 other tissue types and vola! To get the calculation accurate enough take it again every minute...

Hmmm, Well alright. Ok people! I need the tables for nitrogen tissue absorption and half life for ALL human tissue, an abacus, A multi function calculator, A team of math whizzes, 50 gallons of 2.51 bar coffee and five cartons of parliment lights.

Dive-aholic was right, I thought tables could be used as a wheel. Thanks for the info.

be safe and happy diving

 

[sungod357]

No. I think you're trying to figure out how to use the table as a wheel. You don't need to do any mathematical calculations. Plan your initial depth for the length of time you plan on spending there. Then plan your next depth as a 2nd dive with no surface interval. You will need to subtract the residual nitrogen from the NDL at the new depth to come up with your adjusted NDL. Don't forget air consumption. It can shorten your dive times.

Finally - 50ft is not 2 bar, 33ft is 2 bar (look at your own table). 50ft is 2.51 bar.

I stand corrected. Thanks

 

[SeaHorseWoman]

Or just buy a good conservative computer and stay well within its limits....