using "hand-held" type O2 analyzers for deco mixes

[nadwidny]

DGX does not recommend using hand-held O2 analyzers for technical diving applications, and instead recommend using "technical-grade" analyzers have built in compensation for humidity, barometric pressure .

I worked with laboratory grade O2 analyzers that cost $5000 -$7000. None of them had built in compensation for humidity and barometric pressure. We had to do that manually every morning at startup plus calibration with a certified calibration gas (20 cuft of that grade of O2 cost us around $300 IIRC). For DGX to suggest their "technical" grade analyzers can do all that accurately is kinda, well, bs.

 

[seeker242]

Properly calibrated before use, they work fine.
"Properly calibrated" means using a 2 point calibration.

Michael

Alright, but can a typical HH recreational o2 analyzer even do 2 point calibration to begin with?

 

[tursiops]

The impact from humidity is pretty darn minor.

 

[tbone1004]

Alright, but can a typical HH recreational o2 analyzer even do 2 point calibration to begin with?

some of them can yes. Cootwo could though is gone, and there's at least one more who's escaping me that can. It's not really that critical though. 21% is close enough for recreational nitrox mixes, and 100% is close enough for deco mixes. 2 point is really only useful for like 50% deco mixes, but don't need great accuracy for that.

 

[fsardone]

View attachment 586926

Please forgive me for pointing this out but you are not analyzing atmosphere you are analyzing a very dry gas that have been through filters, compression, dehumidification then filtration with a molecular sieve and mixed with pure oxygen.

Now if you have anything more than dry gas in your tank, then you have bigger problems than the oxygen content.

Just my 2c

cheers

 

[tursiops]

Please forgive me for pointing this out but you are not analyzing atmosphere you are analyzing a very dry gas that have been through filters, compression, dehumidification then filtration with a molecular sieve and mixed with pure oxygen.

Now if you have anything more than dry gas in your tank, then you have bigger problems than the oxygen content.

Just my 2c

cheers

Forgive me for pointing out we are talking about calibration, not analysis.

 

[fsardone]

Forgive me for pointing out we are talking about calibration, not analysis.

Well calibrate it with compressed air if you trust the compressor ... and the air it is pumping.
Also the barometric pressure becomes compensated if you calibrate at the same altitude at which you are measuring (unless at the tropics while the eye of a cyclone is going through in which case humidity and change of pressure might kill you other than for the content of oxygen in the tank ...)

 

[tursiops]

Well calibrate it with compressed air if you trust the compressor ... and the air it is pumping.

Good idea, but few of us have compressors, whereas many of us have analyzers that need calibration, and the warm, humid atmosphere is always there for us to use. The corrections I posted aren't hard to apply; do you need instruction?

 

[fsardone]

Good idea, but few of us have compressors, whereas many of us have analyzers that need calibration, and the warm, humid atmosphere is always there for us to use. The corrections I posted aren't hard to apply; do you need instruction?

that is exactly my point. you calibrate to the table for temp and humidity and you measure dry for sure gas. All of us have a breathable air tank ... at least to inflate the dry suit unless of course you live in the tropics were you would need it most for the calibration and not the inflation!

 

[Manatee Diver]

I keep a partially used AL80 with air to calibrate my O2 tester.