Question How to check an analyser O2 cell?

[Agro]

Because the math is a single point of failure. The analyzer is a backup to the math.

Math is not the only mistake you can make.
- Poor gauge. Math sais 200 bar, gauge sais 200 bar, infact it is any other pressure.
- Wrong reading on gauge.
- Wrong Gas, He instead fo O2.
- and so on, and so on.
Yes, I agree, these mistakes should not happen. But in real life they do happen. In this case the analyser is the only one to safe my life.

 

[RedSix]

In this case the analyser is the only one to safe my life.

It is not the only one. There is much more and it is the combination of all these things to make it safe: Maths / good training, reliable gear (gauges, compressor,...), a reliable calibrated analyzer and last but not least your brain. At some points (e.g. blending gases for others or a huge project) it is also of advantage to even have second brain / four eyes.
Every single one can fail. But if all line up, it get's safer.

 

[Agro]

It is not the only one.

You misunderstand me intentionally. I never wrote it's the only one. I wrote the opposite

- Poor gauge. Math sais 200 bar, gauge sais 200 bar, infact it is any other pressure.
- Wrong reading on gauge.
- Wrong Gas, He instead fo O2.
- and so on, and so on

IF these mistakes happen, THEN the analyser is the only one to safe my life.

 

[J-Vo]

A good analyser compansates barometer pressure. Divesoft analysers do so.

I have never seen an analyzer that didn't have a calibration nob. This is both for barometric pressure and cell drift. I've used mine as high as 12,000' (3650m) without even being close to outside the calibration range.

 

[Manatee Diver]

Basically when you can't turn up the calibration to meet 100% (as a known gas) the cell is past its useful life for tech diving. It may have a little life left as a recreational 32% cell analyzer but that's when you replace the cell

Finally got a chance to test to see if it calibrates with oxygen, and it does. So I might have a few months left on this sensor.

 

[Agro]

I have never seen an analyzer that didn't have a calibration nob. This is both for barometric pressure and cell drift. I've used mine as high as 12,000' (3650m) without even being close to outside the calibration range.

ATA Analyser does not compensate for barometric pressure.

 

[broncobowsher]

ATA Analyser does not compensate for barometric pressure.

Yes and no.
Is there an automatic barometric compensation? No.
There is a manual calibration, and this will compensate for barometric pressure. so Yes, it does compensate.

If you get to the basics of it, an analyzer does NOT measure the percentage of O2. It reads partial pressure of O2. Displays a percentage based on calibration. What calibration gas (typically air or pure O2) and pressure (ambient, which may vary with altitude and barometric pressure) make up the calibration. If you change the pressure you test at compared to the pressure you calibrate at, you have garbage data.

 

[Agro]

Yes and no.
Is there an automatic barometric compensation? No.
There is a manual calibration, and this will compensate for barometric pressure. so Yes, it does compensate.

If you get to the basics of it, an analyzer does NOT measure the percentage of O2. It reads partial pressure of O2. Displays a percentage based on calibration. What calibration gas (typically air or pure O2) and pressure (ambient, which may vary with altitude and barometric pressure) make up the calibration. If you change the pressure you test at compared to the pressure you calibrate at, you have garbage data.

I do not call this compensation. It assumes that you always calibrate at exactly the same barometric pressure as you use your analyser. This is no compensation, this is calibration.

Barometric pressure 1 bar:
pO2=0.2, 20% Oxygen, 10mV
pO2=1.0, 100% Oxygen, 50mV
Calibration.
Now we go to altitude, barometric pressure 0.5 bar:
pO2=0.1, 20% Oxygen, 5mV.
Analyser sais 10% Oxygen according to calibration, so it does not compensate for barometric pressure.

Barometric pressure 0.5 bar:
pO2=0.1, 20% Oxygen, 5mV
pO1=0.5, 100% Oxygen, 25mV
Calibration.
Now you analyse your gas at the same barometric pressure, everything is fine. Go down to higher barometric pressure and result is wrong again.

A good analyser does compensate for barometric pressure. Divesoft analyser is measuring barometric pressure and takes it into calculation. You get no garbage data when barometric pressure changes. That's what I call compensation.

You may have different barometric pressure at the same location because of natural change. Who is thinking about that and does recalibrate the analyser? You should do it every 3 hours, wheater including barometric pressure can change as fast as that. Use a Divesoft analyser and forget about barometric pressure.