View Poll Results: How many sensors, less than 1 year old, failed on you last year

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  • 0

    113 54.85%
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    42 20.39%
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    21 10.19%
  • 3

    13 6.31%
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    17 8.25%
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Thread: Sensor failure data

  1. #21
    Fake Diver Jeff Pack will become famous soon enough Jeff Pack will become famous soon enough Jeff Pack will become famous soon enough Jeff Pack will become famous soon enough Jeff Pack's Avatar
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    Re: Sensor failure data

    example


    ATA/ mv/ Expected mv/ percentage difference

    2.0/ 94.4/ 101.7/ -7.7%

  2. #22
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    Re: Sensor failure data

    Quote Originally Posted by Jeff Pack  View Original Post
    example


    ATA/ mv/ Expected mv/ percentage difference

    2.0/ 94.4/ 101.7/ -7.7%
    and what is your reference point? 0.21 or 1.00?
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  3. #23
    Cave Country Dive Shop Jim Wyatt is an unknown quantity at this point Jim Wyatt's Avatar
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    Re: Sensor failure data

    No failures with the rEvo cells.

  4. #24
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    Re: Sensor failure data

    Quote Originally Posted by paulraymaekers  View Original Post
    and what is your reference point? 0.21 or 1.00?
    It appears the software takes mv @21%, and uses that to match to a table of values up to 2 bar. If cell at each point varies greater than 2% from this value it fails.

  5. #25
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    Re: Sensor failure data

    Quote Originally Posted by Jeff Pack  View Original Post
    It appears the software takes mv @21%, and uses that to match to a table of values up to 2 bar. If cell at each point varies greater than 2% from this value it fails.
    not very scientific, as when you calibrate your unit, you set your ref point at 1.00
    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. #26
    Steve Sprague 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster's Avatar
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    Re: Sensor failure data

    Quote Originally Posted by Jeff Pack  View Original Post
    It appears the software takes mv @21%, and uses that to match to a table of values up to 2 bar. If cell at each point varies greater than 2% from this value it fails.
    Since this is kind of my fault if you are using the Narked@90 cell checker spreadsheet....

    Yes, it uses air as the reference and then extrapolates an expected mV at tested PO2 from that reference. There is a good argument that it would be better to use O2 as a reference since it is closer to the operating range in which we are interested. Paul is in the O2 as a reference gas camp I believe. I had an email exchange with John at Narked@90 recently and the decision was made at that time to leave their spreadsheet with air as the reference gas for operational reasons, namely air is fairly easy to get for reference. You may not truly know what is in that O2 bottle, especially if you are away from a trusted O2 supplier.

    If you keep in mind where the numbers are coming from that is OK. The shape of the curve is more important than the slope angle. If it is out of expected mV a few percent but the curve is a straight line then its most likely a calibration error. If the curve has a significant bend to it one way or the other the cell is suspect.

  7. #27
    RBW Member Kristen24060 is on a distinguished road Kristen24060 is on a distinguished road Kristen24060's Avatar
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    Re: Sensor failure data

    Quote Originally Posted by 4ster  View Original Post
    You may not truly know what is in that O2 bottle, especially if you are away from a trusted O2 supplier.

    If you keep in mind where the numbers are coming from that is OK. The shape of the curve is more important than the slope angle. If it is out of expected mV a few percent but the curve is a straight line then its most likely a calibration error. If the curve has a significant bend to it one way or the other the cell is suspect.

    Exactly my thoughts. If we were being scientific, we would have certified reference O2 or a certified reference O2 sensor. Either of those is a little out of my reach, so I like the air extrapolation better and also just look at the curve to see if it is bending over or not.

    We just bought a used Poseidon Mk 6 that came with a whole bunch of vintage cells. Some fail the tests the unit does and some dont. It will be nice to see how they do with the Narked cell checker. I'm wondering if I can find some examples of cells clearly failing the checker, but are passed by the Mk 6....

  8. #28
    Fake Diver Jeff Pack will become famous soon enough Jeff Pack will become famous soon enough Jeff Pack will become famous soon enough Jeff Pack will become famous soon enough Jeff Pack's Avatar
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    Re: Sensor failure data

    Meg Old Cells - a set on Flickr

    Is the data and graph of the cells.

    I dont see any significant slope issues, but again, this is the first time I've looked at this data.

  9. #29
    Steve Sprague 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster is a glorious beacon of light 4ster's Avatar
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    Re: Sensor failure data

    Looking at your test sheet, the cells graphs squiggle a bit - but they all squiggle in a similar manor. That is from a small error in recording the pressure, or in the pressure gauge itself. So if you take the squiggles out the cells look like they are linear.

    The readings are below expected mVolts (from the mV in air reference) as well. I notice that the "O2 in air" number is 21.0. I usually find mine to be around 20.7 (barometric pressure and humidity affect this number). If 20.7 were used the divergence from expected would be less. It could also be that your particular pressure gauge reads a few percent low.

    To get back on topic...
    I have had 2 cell failures in cells less than a year old. It was when there was the Teledyne withdrawal from market and I was trying a new brand of cell because they were offered a little cheaper... Max305s. Serves me right.

  10. #30
    RBW Member Labrax is an unknown quantity at this point Labrax's Avatar
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    Re: Sensor failure data

    No problems with my JJ R17 (Vandagraph) during the first year of use. They are still "flying" like the most trained aerobatic patrol. I am replacing them, one by one, after near two years of service.

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