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

Discussion in 'Technical Diving Specialties' started by Narcoz, May 7, 2020.

  1. nadwidny

    nadwidny Instructor, Scuba

    # of Dives: I just don't log dives
    Location: Cranbrook, BC
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    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.
     
    EireDiver606, Dark Wolf and rjack321 like this.
  2. seeker242

    seeker242 DIR Practitioner

    # of Dives: 200 - 499
    Location: Pompano Beach, FL
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    Alright, but can a typical HH recreational o2 analyzer even do 2 point calibration to begin with?
     
  3. tursiops

    tursiops Marine Scientist and Master Instructor ScubaBoard Supporter

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    Analox Table.JPG
     
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  4. tbone1004

    tbone1004 Technical Instructor ScubaBoard Supporter

    # of Dives: I'm a Fish!
    Location: Greenville, South Carolina, United States
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    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.
     
  5. fsardone

    fsardone Solo Diver ScubaBoard Supporter

    # of Dives: I just don't log dives
    Location: Rome, Italy
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    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
     
    hsinhai, Dark Wolf and Graeme Fraser like this.
  6. tursiops

    tursiops Marine Scientist and Master Instructor ScubaBoard Supporter

    # of Dives: 2,500 - 4,999
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    Forgive me for pointing out we are talking about calibration, not analysis.
     
    fsardone likes this.
  7. fsardone

    fsardone Solo Diver ScubaBoard Supporter

    # of Dives: I just don't log dives
    Location: Rome, Italy
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    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 ...)
     
  8. tursiops

    tursiops Marine Scientist and Master Instructor ScubaBoard Supporter

    # of Dives: 2,500 - 4,999
    Location: U.S. East Coast
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    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? :)
     
  9. fsardone

    fsardone Solo Diver ScubaBoard Supporter

    # of Dives: I just don't log dives
    Location: Rome, Italy
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    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 :wink: unless of course you live in the tropics :cool: were you would need it most for the calibration and not the inflation!
     
  10. Manatee Diver

    Manatee Diver Stop throwing lettuce at me! ScubaBoard Supporter

    # of Dives: None - Not Certified
    Location: Tampa Bay, FL
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    I keep a partially used AL80 with air to calibrate my O2 tester.
     

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