Nitrox: How to calibrate/analyze

[Upwelling]

I recently passed a Nitrox course; at the shop I was taught to analyze by attaching the analyzer to a tank of regular air, adjusting the dial on the analyzer until it reads "20.9" or thereabouts, and then remove the analyzer and place it on the tank containing the EANx mix.

However my friend was telling me that you can just leave the analyer in the open air and calibrate it that way--would anyone be able to give me a step by step procedure for doing it that way? thanks!

 

[The Kraken]

You take the analyzer, hold it up in the plain air and push the "calibrate" button.

 

[OE2X]

When you analyze your gas, you can do it either way. If you do bring the analyzer back to 21% with ambient air, just make sure you are in a room with normal clean air. Ie... you don't want to be in your garage with you car running or on the back of a diesel belching dive boat. Using a tank filled with 21% works fine as well. If you are doing multiple Ean filled tanks it is faster to bring your analyzer back to 21% by putting on a tank with air. Make sure you do so in between tanks filled with Ean.

Calibrating either way is easy. If on the tank, just open the valve until a small steady stream of air goes into the analyzer. When the digital readout becomes fixed on a certain percentage then you adjust the knob until you get the correct readout of 21%. Now your guage is calibrated. You can achieve the same results with your ambient air by holding the analyzer and gently waving it back and forth through the air. This is a bit slower than using the tank method.

 

[Upwelling]

thank you!

When you analyze your gas, you can do it either way. If you do bring the analyzer back to 21% with ambient air, just make sure you are in a room with normal clean air. Ie... you don't want to be in your garage with you car running or on the back of a diesel belching dive boat. Using a tank filled with 21% works fine as well. If you are doing multiple Ean filled tanks it is faster to bring your analyzer back to 21% by putting on a tank with air. Make sure you do so in between tanks filled with Ean.

Calibrating either way is easy. If on the tank, just open the valve until a small steady stream of air goes into the analyzer. When the digital readout becomes fixed on a certain percentage then you adjust the knob until you get the correct readout of 21%. Now your guage is calibrated. You can achieve the same results with your ambient air by holding the analyzer and gently waving it back and forth through the air. This is a bit slower than using the tank method.

 

[matt_unique]

I never calibrate based on a tank because I don't know what's in it. I always calibrate with open air (turn on analyzer, adjust to 20.9, then connect to EAN tank and continue with the process specific to your analyzer). I prefer those with the flow control.

--Matt

 

[Web Monkey]

Since the reading changes with the flow rate, you need to calibrate it to 20.9% using air at the same flow rate as will be used for testing the tank.

Calibrating with non-moving air will give you a reading that's off by several percent.

Terry

I recently passed a Nitrox course; at the shop I was taught to analyze by attaching the analyzer to a tank of regular air, adjusting the dial on the analyzer until it reads "20.9" or thereabouts, and then remove the analyzer and place it on the tank containing the EANx mix.

However my friend was telling me that you can just leave the analyer in the open air and calibrate it that way--would anyone be able to give me a step by step procedure for doing it that way? thanks!

 

[Jason B]

how do you get the correct flow rate across the sensor just holding it in air?

edit: web monkey must have posted as I was posting. Thanks for confirming my thoughts.

Jason

 

[Web Monkey]

You can't. You need to calibrate it against a tank known to contain normal air, and adjust the flow rate using the flow meter (should be there with the O2 analyzer).

The shop will typically have a calibration air cylinder next to the o2 checker just for this purpose.

Terry

how do you get the correct flow rate across the sensor just holding it in air?

edit: web monkey must have posted as I was posting. Thanks for confirming my thoughts.

Jason

 

[emtdan]

Do you think it makes sense to buy a personal analyzer? Should i trust shop analyzers much? I have always thought that they are not sensitive enough.... and have had problems calibrating before because they are faluty....

 

[DPJ]

Do you think it makes sense to buy a personal analyzer? Should i trust shop analyzers much? I have always thought that they are not sensitive enough.... and have had problems calibrating before because they are faluty....

In addition to the issue you raised about the shop, you may need your own if you are provided tanks on a boat. They may or may not have one available for you on the boat.