How accurate is an analyser at high % of oxygen?

[rjack321]

I agree that for most diving it is not required but extremely deep dives need a lot of accuracy (not that I'm doing those, just sayin').

Well when you're doing doc deep level dives the best thing you can do is get your gasses professionally filled by weight. So you aren't in a position where 0.5% kind of discrepancies are flaws.

I did not know divesoft now had up to 3 point calibration.

 

[kensuf]

O2 cells are essentially batteries. Any amount of oxygen turns them "on." The greater the number of oxygen molecules, the higher the output voltage. However, like all batteries, they eventually start to wear down and that upper voltage dwindles. And like all batteries, they eventually die and need to be replaced.

I tend to get about 18 months out of the cell in my analyzer.

 

[Saniflush]

sensors are quite accurate, but they are only considered accurate when close to their calibration gas. I.e. if you calibrate in air and try to analyze O2, then the analysis is not considered accurate due to the lack of linearity in the cells. If you calibrate with pure O2 and try to analyze air, then it's going to be just as wrong. Cells can be off by 5-10% easily, but can also be current limited and not be able to calibrate properly in pure O2.

If you are trying to use your analyzer to analyze a tank with O2 in it, you need to calibrate that analyzer against one of the O2 bottles that they are getting from the gass supplier which will be 99.9%+.

Thank you for answering a question that I was going to pose today. I just had this happen this weekend with a tester calibrated to 21% on a bottle that I knew was 98%-99%. The tester was running about 8% off in it's reading.