+ Reply to Thread
Page 2 of 4 FirstFirst 1 2 3 4 LastLast
Results 11 to 20 of 39

Thread: Understanding Oxygen Sensors by Paul Raymaekers

  1. #11
    CEO DiveNav, Inc. DiveNav will become famous soon enough DiveNav will become famous soon enough DiveNav will become famous soon enough DiveNav will become famous soon enough DiveNav's Avatar
    Join Date
    Nov 2008
    Location
    USA
    Posts
    243

    Re: Understanding Oxygen Sensors by Paul Raymaekers

    Very good report (please put a number next to the figures) .... but scary data

    Now ..... maybe I am saying something stupid here but ...... isn't there a way to "predict" the demise of the sensor?

    Let me explain:

    1) In your paper you said: "... This means that current limiting seems to happen more after the sensor has been used for some time, near the (theoretical) end of life of a sensor, so the likelihood of failure due to current limiting increases when the sensor gets older...."

    2) If (1) is true, then we could extrapolate that a sensor with a lower current limit (your type 3) has an higher likelihood of "passing out" than a sensor with an higher current limit (your type 1).

    3) if (2) is true, then we could "measure" the current limit of the sensor (basically create for each sensor in the rebreather a current/ PPO2 curve - and store it in the dive computer) and use the data for: a) correcting the algorithm calculating the PPO2, and b) warn user of when is time to change a specific O2 sensor.

    4) How do we measure the current limit of the sensor? Easy: calibrate the sensor at the surface with O2 100%, leave O2 100% in the rebreather, grab the old same old OC kit (yes, that noisy tank), make a slow descent to 10m (that should be more than plenty) - WHILE BREATHING FROM THE TANK FILLED WITH AIR.
    Now let your dive computer do all the heavy data crunching (kind of) and spit out a nice curve for each sensor with estimate date (and time) for replacement.

    Repeat (4) every XX number of days

    Again, I apologize If I said something stupid ..... I only dive a virtual rebreather and so far I never had an O2 sensor failure

    Alberto (aka eDiver)





  2. #12
    rEvo's daddy
    paulraymaekers has a reputation beyond repute paulraymaekers has a reputation beyond repute paulraymaekers has a reputation beyond repute paulraymaekers has a reputation beyond repute paulraymaekers has a reputation beyond repute paulraymaekers has a reputation beyond repute paulraymaekers has a reputation beyond repute paulraymaekers has a reputation beyond repute paulraymaekers has a reputation beyond repute paulraymaekers has a reputation beyond repute paulraymaekers has a reputation beyond repute paulraymaekers's Avatar
    Join Date
    May 2005
    Location
    belgium
    Posts
    4,073
    rEvo

    Re: Understanding Oxygen Sensors by Paul Raymaekers

    Quote Originally Posted by DiveNav  View Original Post
    ...
    3) if (2) is true, then we could "measure" the current limit of the sensor (basically create for each sensor in the rebreather a current/ PPO2 curve - and store it in the dive computer) and use the data for: a) correcting the algorithm calculating the PPO2, and b) warn user of when is time to change a specific O2 sensor.

    4) How do we measure the current limit of the sensor? Easy: calibrate the sensor at the surface with O2 100%, leave O2 100% in the rebreather, grab the old same old OC kit (yes, that noisy tank), make a slow descent to 10m (that should be more than plenty) - WHILE BREATHING FROM THE TANK FILLED WITH AIR.
    Now let your dive computer do all the heavy data crunching (kind of) and spit out a nice curve for each sensor with estimate date (and time) for replacement.

    Repeat (4) every XX number of days

    Again, I apologize If I said something stupid ..... I only dive a virtual rebreather and so far I never had an O2 sensor failure

    Alberto (aka eDiver)


    real divers do this test when they dive as it says in the article: on a regular basis you check your sensors for current limiting

    as for perfect prediction: in the ideal world maybe yes, in the real world, as in the article, there are more failure types then only current limiting..
    www.rEvo-rebreathers.com
    ...."Yes you have to pre-breathe to activate the scrubber sorb, anyone who says different doesn't know what they are talking about!"...
    .... to get more accurate CO2 injection in the breathing machine we put 2 mass flow controllers in series ...
    .... The noise is a few tens of nano-volts, so DL were able to reduce the output voltage ...
    .... radial scrubbers give longer dwell time than axials...
    .... the earth is flat and ...

  3. #13
    RBW Member Packhorse is a glorious beacon of light Packhorse is a glorious beacon of light Packhorse is a glorious beacon of light Packhorse is a glorious beacon of light Packhorse is a glorious beacon of light Packhorse is a glorious beacon of light Packhorse is a glorious beacon of light Packhorse is a glorious beacon of light Packhorse is a glorious beacon of light Packhorse is a glorious beacon of light Packhorse is a glorious beacon of light Packhorse's Avatar
    Join Date
    Jan 2008
    Location
    Auckland New Zealand
    Posts
    1,647
    rEvoIII mini hCCR

    RG-UMF,IDA 71,rEvo mCCR

    Re: Understanding Oxygen Sensors by Paul Raymaekers

    Quote Originally Posted by DiveNav  View Original Post


    4) How do we measure the current limit of the sensor? Easy: calibrate the sensor at the surface with O2 100%, leave O2 100% in the rebreather, grab the old same old OC kit (yes, that noisy tank), make a slow descent to 10m (that should be more than plenty) - WHILE BREATHING FROM THE TANK FILLED WITH AIR.
    Now let your dive computer do all the heavy data crunching (kind of) and spit out a nice curve for each sensor with estimate date (and time) for replacement.

    Repeat (4) every XX number of days

    Again, I apologize If I said something stupid ..... I only dive a virtual rebreather and so far I never had an O2 sensor failure

    Alberto (aka eDiver)


    Or build a small pressure pot, put your cells in it and fill will O2 to a pressure of2 bar absolute.

    http://www.rebreatherworld.com/showthread.php?t=29787

  4. #14
    Phil Siswick, Tango PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick's Avatar
    Join Date
    Apr 2006
    Location
    Oxford, UK
    Posts
    1,742
    JJ-CCR

    APD Inspiration, Evolution

    Re: Understanding Oxygen Sensors by Paul Raymaekers

    Quote Originally Posted by Packhorse  View Original Post
    Or build a small pressure pot, put your cells in it and fill will O2 to a pressure of2 bar absolute.

    http://www.rebreatherworld.com/showthread.php?t=29787
    Or, if you're not technically gifted (or at least not to deal with the pressures involved), buy a unit that has a head that can do cell testing or an external cell checker.

    IIRC, the HH has a cell checker, as does the Narked@90 Deep Pursuit. I went for the Narked@90 Mini Checker - a very nice bit of kit indeed.

    Paul,

    Thanks for an excellent article - it summarises the issue(s) very nicely.

    Cheers,

    Phil

  5. #15
    rEvo's daddy
    paulraymaekers has a reputation beyond repute paulraymaekers has a reputation beyond repute paulraymaekers has a reputation beyond repute paulraymaekers has a reputation beyond repute paulraymaekers has a reputation beyond repute paulraymaekers has a reputation beyond repute paulraymaekers has a reputation beyond repute paulraymaekers has a reputation beyond repute paulraymaekers has a reputation beyond repute paulraymaekers has a reputation beyond repute paulraymaekers has a reputation beyond repute paulraymaekers's Avatar
    Join Date
    May 2005
    Location
    belgium
    Posts
    4,073
    rEvo

    Re: Understanding Oxygen Sensors by Paul Raymaekers

    Quote Originally Posted by PhilSiswick  View Original Post
    Or, if you're not technically gifted (or at least not to deal with the pressures involved), buy a unit that has a head that can do cell testing or an external cell checker.

    IIRC, the HH has a cell checker, as does the Narked@90 Deep Pursuit. I went for the Narked@90 Mini Checker - a very nice bit of kit indeed.

    Paul,

    Thanks for an excellent article - it summarises the issue(s) very nicely.

    Cheers,

    Phil
    just remind that connectors only have a limited number of connections/disconnetions

    as far as I remember from the molex data sheet: gold plated connectors have a 50 connection/disconnetion cycle lifetime

    and be sure that if you take out sensors, do not drop them...
    www.rEvo-rebreathers.com
    ...."Yes you have to pre-breathe to activate the scrubber sorb, anyone who says different doesn't know what they are talking about!"...
    .... to get more accurate CO2 injection in the breathing machine we put 2 mass flow controllers in series ...
    .... The noise is a few tens of nano-volts, so DL were able to reduce the output voltage ...
    .... radial scrubbers give longer dwell time than axials...
    .... the earth is flat and ...

  6. #16
    It's Hammertime! Pawel Szopinski is a name known to all Pawel Szopinski is a name known to all Pawel Szopinski is a name known to all Pawel Szopinski is a name known to all Pawel Szopinski is a name known to all Pawel Szopinski is a name known to all Pawel Szopinski is a name known to all Pawel Szopinski is a name known to all Pawel Szopinski is a name known to all Pawel Szopinski is a name known to all Pawel Szopinski is a name known to all Pawel Szopinski's Avatar
    Join Date
    Feb 2008
    Location
    London, United Kingdom
    Posts
    783
    Hammerhead

    Megalodon, Inspiration

    Re: Understanding Oxygen Sensors by Paul Raymaekers

    Quote Originally Posted by paulraymaekers  View Original Post
    and be sure that if you take out sensors, do not drop them...
    What about hundreds of cells posted in envelops and abused in transit?
    Hammerhead CCR Instructor
    Hammerhead Repair Facility
    Golem Gear Dealer
    www.silentthrill.com

  7. #17
    RBW Key Holder
    Curt Bowen has a reputation beyond repute Curt Bowen has a reputation beyond repute Curt Bowen has a reputation beyond repute Curt Bowen has a reputation beyond repute Curt Bowen has a reputation beyond repute Curt Bowen has a reputation beyond repute Curt Bowen has a reputation beyond repute Curt Bowen has a reputation beyond repute Curt Bowen has a reputation beyond repute Curt Bowen has a reputation beyond repute Curt Bowen has a reputation beyond repute Curt Bowen's Avatar
    Join Date
    Jun 2005
    Location
    USA, Florida
    Posts
    2,980
    KISS CLASSIC

    Megalodon, Kiss Sport

    Re: Understanding Oxygen Sensors by Paul Raymaekers

    Narked at 90 Mini-Check©


    See Narked at 90 personal cell checker above

  8. #18
    RBW Member Packhorse is a glorious beacon of light Packhorse is a glorious beacon of light Packhorse is a glorious beacon of light Packhorse is a glorious beacon of light Packhorse is a glorious beacon of light Packhorse is a glorious beacon of light Packhorse is a glorious beacon of light Packhorse is a glorious beacon of light Packhorse is a glorious beacon of light Packhorse is a glorious beacon of light Packhorse is a glorious beacon of light Packhorse's Avatar
    Join Date
    Jan 2008
    Location
    Auckland New Zealand
    Posts
    1,647
    rEvoIII mini hCCR

    RG-UMF,IDA 71,rEvo mCCR

    Re: Understanding Oxygen Sensors by Paul Raymaekers

    Quote Originally Posted by paulraymaekers  View Original Post
    just remind that connectors only have a limited number of connections/disconnetions

    as far as I remember from the molex data sheet: gold plated connectors have a 50 connection/disconnetion cycle lifetime

    and be sure that if you take out sensors, do not drop them...
    Paul,

    what are you thoughts on a sealable high quality plug so you could unplug the entire cell tray from the rEvo and place it in a cell checker. I guess you could use a in line fisher plug and socket?

  9. #19
    Brent - Narked at 90
    divetheworld has a reputation beyond repute divetheworld has a reputation beyond repute divetheworld has a reputation beyond repute divetheworld has a reputation beyond repute divetheworld has a reputation beyond repute divetheworld has a reputation beyond repute divetheworld has a reputation beyond repute divetheworld has a reputation beyond repute divetheworld has a reputation beyond repute divetheworld has a reputation beyond repute divetheworld has a reputation beyond repute divetheworld's Avatar
    Join Date
    Mar 2005
    Location
    Prescot, England
    Posts
    2,423
    Deep Pursuit or a Camelion

    and 11 others inc. a UT-240

    Re: Understanding Oxygen Sensors by Paul Raymaekers

    Quote Originally Posted by paulraymaekers  View Original Post
    just remind that connectors only have a limited number of connections/disconnetions

    as far as I remember from the molex data sheet: gold plated connectors have a 50 connection/disconnetion cycle lifetime
    Which is a bit strange in my opinion.

    The SMB Amphenol/Tyco/Radiall all give about 500 mating cycles durability and have the same micron thickness of gold on them.
    We found that the worst change in connector impedance was 10milliohms after exceeding the manufacturers spec. But the Molex is rated to 1/10th of the same durability.
    It's a poor connector IMHO and we should have got away from them ages ago.

    Back to the document.
    I think it's a superb compendium of the information on cells in one document.
    Applause for publishing it.

    Brent
    Copying skips understanding. Understanding is how you grow. You have to understand why something works or why something is how it is. When you copy it, you miss that. WWW.NARKEDAT90.COM
    www.puwer.co.uk PUWER and Machinery CE Marking www.ce-eu.com

  10. #20
    RBW Member Mike_Eitel is an unknown quantity at this point Mike_Eitel's Avatar
    Join Date
    May 2006
    Location
    Switzerland
    Posts
    221
    MeCCRxWi

    MeRAY, MeTravox,MeCCRV"x,Inspi

    Re: Understanding Oxygen Sensors by Paul Raymaekers

    Congratulations Paul

    I only want to add something i learnde from an old developer from AII labs.

    The sensors hate to get revers currents. Means they get easily damaged when your electronics "reinjects" current into the sensor. ( even low or short spikes ).

    After I learned that , I modified my electronics .... Less defecive sensors, lasting longer.

    Mike

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts