Looking for CNS Formula

[scubanimal]

Does anyone know the formula for calculating CNS%? I tried several searches but have not found one yet.
Thanks,

 

[jtivat]

%CNS = Time at Depth / NOAA Single Exposure Time at PO2 for Specific Depth x 100

 

[Charlie99]

As usual, Erick Baker comes to the rescue ....

 

[Diver0001]

There are also tables you can use. What the tables/formulas don't tell you is that 80% is the maximum CNS you should work with for one day.

R..

 

[WarmWaterDiver]

As usual, Erick Baker comes to the rescue ....

Thanks Charlie. Nice attachment.

What year was this written? Seeing suggested FORTRAN programming code evoked some nostalgia. I haven't programmed anything using FORTRAN since 1990.

 

[scubanimal]

Thanks guys, I must be old, I stopped using fortran in '85. I tried the formula, but the numbers I get are way different then my tables. Not sure why. I'm trying to create a excel spreadsheet for my dive slate (plan).

Any other thoughts?

Thanks again.

 

[Diver0001]

Thanks guys, I must be old, I stopped using fortran in '85. I tried the formula, but the numbers I get are way different then my tables. Not sure why. I'm trying to create a excel spreadsheet for my dive slate (plan).

Any other thoughts?

Thanks again.

If you're just making a spreadsheet then you don't need a formula. Just use a lookup table. I have an old diveplanner I made in excel that does it like that. You're welcome to have it if you want.

R..

 

[Charlie99]

If you're just making a spreadsheet then you don't need a formula.

that basically what Erik Baker did in that article. He used the NOAA limits that NOAA provides at 0.1ata increments, and linearly interpolated for points between them. To do that in Fortran he generated a series of intercepts and slopes for the various straight line segments.

That 80% max limit for repetive dives seems to be an IANTD thing. NOAA has separate tables for 24 hour limit and single dive limits.

For example, NOAA has single dive limit of 45 minutes at 1.6ppO2, but allows 150 minute over a 24 hour period. For 1.4ppO2, the limits are 150 minutea nd 180 minutes.

Repetive dive CNS calculations get even more interesting if one chooses to assume that the effects decay exponentially with a half time of either 90 minutes (as do a lot of dive computers) or 60 minutes (as do some Suunto computers).