Calibrating Analox O2EII - How often do you need to calibrate the analyzer?

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BoltSnap

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Does one need to calibrate the analyzer after each Tank Nitrox Test and start from 20.9% in the same session (after the initial calibration and first Nitrox Tank test, do I need to go back and calibrate the analyzer at 20.9% before I can test the next Nitrox Tank)?
 
If I'm checking a bunch of tanks I usually recalibrate every 3 to 4 tanks. Unless I get an unexpected reading- then I'll recalibrate and recheck that tank.
 
Do you wait for the reading in the analyzer to go down to a certain reading or you just go on the next tank regardless?
 
I don't wait for it to get all the way back to 20.9, I'll usually go to the next one once it gets in to the lower 20's.

I should note note that when I'm doing this it's on tanks that are filled from premixed banks. They will normally be within a half percent or so over the whole batch. If you're checking tanks that are individually mixed then it's probably better to zero out after each one.
 
If you recalibrate the analyzer between nitrox tanks you are likely to be uncalibrating it. It takes awhile for the sensor to return to 20.9 when it has been in a high oxygen environment and calibrating at that time will tell the analyzer that the higher o2 level is 20.9. If you then wait awhile with the sensor in air it will go below 20.9 or if you check another nitrox tank it will read it as lower than it is.
 
At the LDS where I get my fills there is usually a fan running near the fill station. Placing the analyzer in the edge of the air stream drops it quickly, remove from the air stream and let settle for a couple of seconds, and good to go. Fills are from banked gas.
 
If you recalibrate the analyzer between nitrox tanks you are likely to be uncalibrating it. It takes awhile for the sensor to return to 20.9 when it has been in a high oxygen environment and calibrating at that time will tell the analyzer that the higher o2 level is 20.9. If you then wait awhile with the sensor in air it will go below 20.9 or if you check another nitrox tank it will read it as lower than it is.

and BRT is our WINNER! :D

The O2EII only needs to be calibrated once per session, regardless of how many tanks you are checking. Turn it on, calibrate it, then check 1 or 50 tanks...do NOT wait :no: for the analyzer to settle back to 20.9 between checks as the O2 content of the next tank will flush out the last tank reading automatically.

Dive Safe!
 
and BRT is our WINNER! :D

The O2EII only needs to be calibrated once per session, regardless of how many tanks you are checking. Turn it on, calibrate it, then check 1 or 50 tanks...do NOT wait :no: for the analyzer to settle back to 20.9 between checks as the O2 content of the next tank will flush out the last tank reading automatically.

Dive Safe!

I was afraid to admit that I just moved it from tank to tank like that but it always seems to give good readings.
 

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