What ppO2 do you use and why?

[NAM001]

try it out and correct me if i am wrong. But wouldnt the 1% error be on the depth presure and not the ppo2.

ie if at 100 ft or 4atm on .32 wouldnt the error be 1% of the 4 atm , not the ppo2 0r .04 in this case not 1.28 ppo2 I agree not detail to war over butwould cause enough of an error to be perhaps 1/2 %.

1% error remains 1% error even at depth. So your 1.4 could become a 1.414 at most. Not a 1.5.

 

[dfx]

try it out and correct me if i am wrong. But wouldnt the 1% error be on the depth presure and not the ppo2.

ie if at 100 ft or 4atm on .32 wouldnt the error be 1% of the 4 atm , not the ppo2 0r .04 in this case not 1.28 ppo2 I agree not detail to war over butwould cause enough of an error to be perhaps 1/2 %.

I would love to either agree or disagree with this, but I don't understand a word of it.

 

[NAM001]

the error is incurred on the depth ie at 100 ft the depth would be 4 atm and not the resultant of ppo2 od 1.28

 

[gcarter]

The measurment error is on FO2, NOT PPO2. For 32% @100', PPO2 is 1.29, for 31% it is 1.25, and for 33% it is 1.33. the delta in PPO2 is +/- .04 for a 3.1% error.

---------- Post added August 5th, 2013 at 04:51 PM ----------

The measurment error is on FO2, NOT PPO2. For 32% @100', PPO2 is 1.29, for 31% it is 1.25, and for 33% it is 1.33. the delta in PPO2 is +/- .04 for a 3.1% error.

All of with means little if diving with appropriate conservatism.

 

[gekodivebali]

Main thing with analysers is the calibration. Most divers ignore that when calibrated in normal air, analysers should not always be set to 20.8 or 20.9.
Temperature and humidity will affect the readings. In warm, moist climes the calibration setting should be as low as 20.5 or 20.6. That makes a huge difference on the reading displayed by the analyser for the actual mix.
This is not taught in most Nitrox courses. Agencies pass the responsibility onto the manufacturers by saying one should read the instructions. At the same time, most divers do not own analysers and have no access to manuals...
This is much more worrying than a +-1% reading tolerance!

---------- Post added August 6th, 2013 at 03:11 PM ----------

Also not sure what analysers display no decimals. Please let me know, I'm curious...

 

[ajduplessis]

Huh? Lets say an O2 analyzer has an error of 1%, so instead of NTX32 you are diving NTX33. For a 130 foot dive, the 32 will give you a 1.58 PPO2. The 33% will give you a 1.63 PPO2. Partial Pressure is not described in terms of percentages, so an analyzer error wouldn't correspond directly with a change in PPO2.

Well in your case a 1% error is going to have a even bigger impact!! Still not sure about the PADI, SDI comment.

2.0 on deco
1.8 during the dive
1.6 if I'm working (hydraulic drilling, etc.)

I only dive warm water, so cold water limits would be moot.

Who teaches 1.4? I'm a PADI and SDI nitrox instrustor, and I teach 1.6.

 

[Dr. Lecter]

In warm, moist climes the calibration setting should be as low as 20.5 or 20.6.

The easy way to fix that issue is to calibrate using tank air at the same flow rate as the rate at which you'll be testing.

 

[gekodivebali]

True but most don't! & you need to be 100% sure to have 21% in the tank.
In practice, most divers calibrate to 20.9% in ambient air. That includes instructors.

 

[NAM001]

I sometimes usae a tank of cal gas. Nothing more than a 3 cu ft bottle of compressed air. No humidity issue as it is the same as in the tank being checked. If i am diving less than 1.0 ppo2 ,, i dont bother with it. I just use atmosphere.

 

[Wookie]

Well in your case a 1% error is going to have a even bigger impact!! Still not sure about the PADI, SDI comment.

I looked it up. Both PADI and SDI recommend 1.4. It's been a while since I taught Nitrox. Longer since I learned it. When I took a nitrox class, PADI still was hell bent against it.