Nitrox tables

[pilot fish]

And actually, there is a setting in the Set 2 area of the computer, called "FO2 50" which you can toggle on or off. When on, you must set your O2 percentage for each dive after diving nitrox, or else it will default to a 21% for nitrogen loading, but 50% for O2 loading... to try to keep you safe on both sides since you didn't tell the poor computer what the next gas was...

If you toggle this feature off, it will always default to your last dive settings as long as it was recent enought that the computer is still on... So for example, if you know you are always going to get the same mix tank after tank, Set FO2 50 off, and then you can just set it before the first dive of the day, and the settings stay for your repetitive dives.

OK, I've done that so it will stay at the % of my last 02 mix. Thanks

 

[pilot fish]

Now you begin to see why you have to learn the gas laws, the formulas, and how it all applies. Once you understand all of this good stuff, you become master of the computer rather than it being your master. You are on the road to creating a useful tool out of what could have become a dangerous monster.
In most cases, you change your O2 percent to match your dive, in some cases, after you understand what's going on, you may make decisions that change your safety margins, hopefully (usually) to the more conservative side.

Tom

I'm the Master of my puter, I'm the Captain of my gas blend. Thanks

 

[The Kraken]

Pilot,
Here is a list of the formulae which I like to play with from time to time and that I also go through when planning my dives.
Hope you will take them and put them to good use.
All of the abbreviations are listed at the end of the list of formulae.

Atmosphere Absolute:
ATA = (D/33) + 1

Best Mix
BM = PO2 / fG

Depth
D = (ATA - 1) x 33

Equvalent Air Depth
EAD = (((1 - fG) / .79) x (D + 33)) - 33

Maximum Operating Depth (Of O2)
MOD = PO2 / fG

Pressure of Gas
PG = fG x ATA

Surface Air Comsumption Rate
SAC = (((Pb - Pe) / Pb) x ((Pb / Pw) x V) / T) / ((D / 33) + 1)

Gas Used at Depth
USE = SAC x T x ((D / 33) + 1)

Time of Dive Based on Available Volume of Breathing Gas
TIM = V / ((D / 33) + 1) x SAC

Volume (Actual Volume of Gas Based Upon Fill Pressure)
VOL = (Pb / Pw) X Vn

Where:
ATA = Atmosphere Absolute
BM = Best Mix
D = Depth
EAD = Equivalent Air Depth
fG = Fraction of Gas (ie .32 or 32%)
Pb = Beginning Pressure of Tank
Pe = Ending Pressure of Tank
Pw = Working Pressure of Tank
PO2 = Partial Pressure of Oxygen
SAC = Surface Air Consumption Rate
T = Time
V = Volume
Vn = Nominal Volume of Tank

Hope these help . . .

Safe dives, safer ascents . . .

 

[Nomaster]

Pilot,
Here is a list of the formulae which I like to play with from time to time and that I also go through when planning my dives.
Hope you will take them and put them to good use.
All of the abbreviations are listed at the end of the list of formulae. . .

Hope these help . . .

Safe dives, safer ascents . . .

Kraken,
I copied them, but now have to translate them to metric.
I can not understand why we in the US insist on using imperial,
it is sssooo confusing.

Tom

 

[The Kraken]

We were supposed to have converted completely to metric years ago, but . . . .

 

[Nomaster]

We were supposed to have converted completely to metric years ago, but . . . .

Yeah, but my feelings about that mess belong in "Whine and Cheese."
Tom

 

[LazyKevin]

Equvalent Air Depth
EAD = (((1 - fG) / .89) x (D + 33)) - 33

You had a typo....

Equvalent Air Depth
EAD = (((1 - fG) / .79) x (D + 33)) - 33

Kevin

 

[The Kraken]

Thank you, very, very much !!!!
Good eye, there . . .
I'll edit and make the correction.

Anyone that copied these formulae, PLEASE, PLEASE take note and make the change to the correct percentage.

 

[Charlie99]

Rather than use an equivalent air depth table, I find it more convenient to go the other way, using an equivlent NITROX depth table.

As the name implies, it converts the even 10' increments of air depth found on most tables into the equivalent depth when using various nitrox mixes.

Equiv. Nitrox Depth (in ft) = {[(air depth + 33') * 0.79]/(1-FO2)} - 33'

YMMV

Charlie

 

[The Kraken]

Agreed, but doing with the EAD and using The Wheel you can work to 5' depth increments.

To each our own . . .