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Thread: Pondering simplicity: analog o2 monitoring?

  1. #1
    Thinker n Tinkerer Sparedone is an unknown quantity at this point Sparedone's Avatar
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    Pondering simplicity: analog o2 monitoring?

    Welcome to a post where the 1950s meet a youngsters musings as I'm adding a ppo2 monitor to a o2 breather build.

    Concept: Use analog mv readings for ppo2 monitoring.

    Benefit: fewer failure points due to reduced components.

    Design concept: Cell, potentiometer at the cell, cable gland, cable, potted needle gauge.

    Even the most basic digital ppo2 meter adds complexity to the simple process of displaying a calibrated a mv reading off the cell.

    Why not a potted analog needle guage run off a cell directly? No battery to change, flood or fail. No lcd display to burn out, no circuitry to corrode. Sure, you can't expect accuracy from an needle gauge while invertered or after smashing it with a rock. Also they also don't like water, but with no battery to change they could be epoxy entombed.

    What else am I needing to learn before I stick two on my build?

    Thanks for considering a tinkerer's pondering.

    Regards,
    Cameron

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    RBW Member Sven Becker is an unknown quantity at this point Sven Becker's Avatar
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    Re: Pondering simplicity: analog o2 monitoring?

    Has been done on Prism Topaz.
    See this link
    http://www.therebreathersite.nl/05_R...rebreather.htm

    Check also the abbrevation PRISM in the text!!!
    Regards
    Sven Becker

    Skickat från min E6553 via Tapatalk

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    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: Pondering simplicity: analog o2 monitoring?

    The conversations I've had with PRISM divers about the analog gauge have had two main points:

    1) It is about as simple as you can get, and thats a good thing.

    2) The meter itself is delicate and care must be taken against accidental knocks, which is hard to do with dive equipment.

    I think I would put the analog meter in something where I could replace it if it got damaged instead of potting it so that everything had to be replaced if the meter were damaged.

  4. #4
    Thinker n Tinkerer Sparedone is an unknown quantity at this point Sparedone's Avatar
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    Re: Pondering simplicity: analog o2 monitoring?

    Thanks for the post, and welcome to this forum.

    The prism acronym is a great piece of trivia!

    Thanks for the topaz reference, I'll try searching the forum for more feedback about their backup gauge.

    Good to know it was implemented by some brilliant builders in the somewhat recent history. Makes me feel less crazy to suggest it's advantages.

    All the best,
    Cameron


    Ps. Is there somewhere I can learn more about your sidemount kiss unit?

  5. #5
    Reads fine print (mostly) Skipbreather has a brilliant future Skipbreather has a brilliant future Skipbreather has a brilliant future Skipbreather has a brilliant future Skipbreather has a brilliant future Skipbreather has a brilliant future Skipbreather has a brilliant future Skipbreather has a brilliant future Skipbreather has a brilliant future Skipbreather has a brilliant future Skipbreather has a brilliant future Skipbreather's Avatar
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    Re: Pondering simplicity: analog o2 monitoring?

    Quote Originally Posted by Sven Becker  View Original Post
    Has been done on Prism Topaz.
    See this link
    http://www.therebreathersite.nl/05_R...rebreather.htm
    Which was a modernization of this:

    http://www.therebreathersite.nl/11_C...5/DSCN2545.jpg

    What the OP is asking about was done a half century ago as the PPO2 readout of the original Biomarine CCR 1000/ MK 15. For those not familiar, the analog readout was powered solely by the output of the cells, which was one of the reasons they used high output 25 mv cells. The calibration procedure did indeed require, as OP envisioned, accessing potentiometers and adjusting them w/ a small screwdriver.

  6. #6
    Thinker n Tinkerer Sparedone is an unknown quantity at this point Sparedone's Avatar
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    Re: Pondering simplicity: analog o2 monitoring?

    Quote Originally Posted by 4ster  View Original Post
    The conversations I've had with PRISM divers about the analog gauge have had two main points:

    1) It is about as simple as you can get, and thats a good thing.

    2) The meter itself is delicate and care must be taken against accidental knocks, which is hard to do with dive equipment.

    I think I would put the analog meter in something where I could replace it if it got damaged instead of potting it so that everything had to be replaced if the meter were damaged.

    Thank you for saving me a ton of digging through conversations.


    With the fragile nature of the gauge might they be housed ambiently on the breathing loop like a HUD since I'm decent at not swimming headfirst into rocks generally?

    That doesn't help me sitting on it, or someone's weightbelt dropping on it while topside.

    On the topic if accidental knocks, do you recall if they mentioned if a predive check and calibration show it's been damaged or might it not show up till the needle sticks at a higher reading when things go pearshaped? I'd like to avoid the hassle of checking the full meter range predive if failure isn't that subtle.

    Thanks for adding to the collective thought.
    Cameron

  7. #7
    Thinker n Tinkerer Sparedone is an unknown quantity at this point Sparedone's Avatar
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    Re: Pondering simplicity: analog o2 monitoring?

    Quote Originally Posted by Skipbreather  View Original Post
    Which was a modernization of this:

    http://www.therebreathersite.nl/11_C...5/DSCN2545.jpg

    What the OP is asking about was done a half century ago as the PPO2 readout of the original Biomarine CCR 1000/ MK 15. For those not familiar, the analog readout was powered solely by the output of the cells, which was one of the reasons they used high output 25 mv cells. The calibration procedure did indeed require, as OP envisioned, accessing potentiometers and adjusting them w/ a small screwdriver.

    Yes sir! Or rather BINGO!

    ....And thanks for stopping by. What are your thoughts on going this route.

  8. #8
    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: Pondering simplicity: analog o2 monitoring?

    Quote Originally Posted by Sparedone  View Original Post
    With the fragile nature of the gauge might they be housed ambiently on the breathing loop like a HUD since I'm decent at not swimming headfirst into rocks generally?

    On the topic if accidental knocks, do you recall if they mentioned if a predive check and calibration show it's been damaged or might it not show up till the needle sticks at a higher reading when things go pearshaped? I'd like to avoid the hassle of checking the full meter range predive if failure isn't that subtle.
    Think about if a mechanical device with a jeweled movement for the needle would do well in a high humidity environment. I don't think it would. I think it would be better in a sealed environment.

    I think the mechanical gauge would pretty much either function or not and that you could tell that when you calibrate. That only comes from my limited experience with wig-wag volt meters, not from diving one.

  9. #9
    Thinker n Tinkerer Sparedone is an unknown quantity at this point Sparedone's Avatar
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    Re: Pondering simplicity: analog o2 monitoring?

    Excellent reminder. Thank you.

    Would an old can light head be the ideal enclosure?

    As for the voltmeter....

    Screenshot_2016-06-19-15-03-44.jpg

    Any cautions?

  10. #10
    RBW Member michael-fisch is on a distinguished road michael-fisch is on a distinguished road michael-fisch's Avatar
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    Re: Pondering simplicity: analog o2 monitoring?

    a zero to 2V voltmeter is not usable with a 25mv O2 sensor since a high pO2 of 1.6bar would yield slightly less than 200mv or less than 1/10 of the full range deflection on the voltmeter. Also as long as the impedience of the voltmeter is not quite high, it will end up destroying the O2 cells within a short time.

    Michael

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