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Thread: Pondering simplicity: analog o2 monitoring?

  1. #31
    King of the Geeks
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    Re: Pondering simplicity: analog o2 monitoring?

    Quote Originally Posted by Sparedone  View Original Post
    .....snip.....

    And if you indeed respawned I seem to be missing my equipment loadout, something you can rectify along with your investment in my million dollar business strategy.


    In other news, here's the guage.
    Attachment 41685

    You're right there... I've always said, when I die, there will be one HELL of a Garage Sale going on...

    Gauge looks cool. Keep us posted!

    Kevin.

  2. #32
    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?

    Quote Originally Posted by heyydude  View Original Post
    You're right there... I've always said, when I die, there will be one HELL of a Garage Sale going on...

    Gauge looks cool. Keep us posted!

    Kevin.
    Don't forget the prayer "Oh God, when I die, don't let my wife sell my dive gear for what I told her I paid for it."

    Michael

  3. #33
    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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    Unhappy Re: Pondering simplicity: analog o2 monitoring?

    Quote Originally Posted by michael-fisch  View Original Post
    Don't forget the prayer "Oh God, when I die, don't let my wife sell my dive gear for what I told her I paid for it."

    Michael

  4. #34
    One Breath From Death testuser is an unknown quantity at this point testuser's Avatar
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    Re: Pondering simplicity: analog o2 monitoring?

    Quote Originally Posted by Sparedone  View Original Post
    Sadly not... an impedance issue if I were to hazard a guess. Give a man a fish?

    And yes, thankfully the irrelevance of ppo2 comment was tongue in cheek.
    Yes you could think of it as an impedance issue. The output of one of these (high output: http://aii1.com/product/rebreather-o...-psr-11-33-nm/) galvanic PO2 cells is ~25mV in air, but unfortunately that's with almost no current. I can't find a spec easily, but as I recall they are in the range of microAmps. They are not really 'ideal' voltage sources (i.e. they have an internal series resistance) to start with, and most have a temperature compensation resistor divider on the output as well.

    So as a thought expirament, let's say .25mV/10uA = 2.5kOhm internal resistance. If you remember KVL, you're adding the readout gauge resistance to the internal resistane and measuring the voltage across the gauge resistance. So our theoretical 25mv cell, now driving a 10kOhm load will be down to like ~20mV. which is, I'm sure you'd agree, a bad thing. Now if you had a magic circuit with a 1MOhm resistance (say, like most Op-Amps), then your voltage would be like 24.9mV and you're happy.

    All these numbers are notional but the theory is the same. You can see the reason they had to make jeweled movements so they could get the drive current down low enough to not impact the measurement.

    HTH,
    -James

    P.S. if you are looking for a RB loop etc. to make a project O2rig out of, I have a nearly complete Dolphin I bought off eBay for some other pneumatics a year ago I'd be willing to sell cheaply. I think all it's missing is the 1st stage and OPV, though I've never had a full one to start with.

  5. #35
    RBW Member AndrewDonn is on a distinguished road AndrewDonn is on a distinguished road AndrewDonn's Avatar
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    Re: Pondering simplicity: analog o2 monitoring?

    Quote Originally Posted by wedivebc  View Original Post
    I assume from your posts here you have some steam punk fetish or something.


    I don't know why 'yall are knocking the Mk15 secondary. I still dive mine!

  6. #36
    Thinker n Tinkerer Sparedone is an unknown quantity at this point Sparedone's Avatar
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    Re: Pondering simplicity: analog o2 monitoring?

    On the topic of ambient housings and taking my toaster for a swim.

    Discovered another analog gauge setup:

    http://www.therebreathersite.nl/11_C...lectrolung.htm

    "The electronics compartment was vented via a small canister of silicagel with the rest of the system. A standpipe for the vent orifice prevented any accumulated moisture in the canister plenum from being pushed into the electronics"

    I've placed the orders on fleabay to build a traditional digital monitoring system but this project I'll see through.

    Currently planning dual analog guages mounted ambient along with the sensors next to the DSV with a sponge and silica packs for the moisture. A HUD's ugly cousin for redundancy. Off to the rebreather plumbing store once it all arrives for a couple Ts and 90°s.


    With this latest design turn I think a mandatory apology to the homebuild community is needed. However, thank you all for helping educate me.

    Regards,
    Cameron

    Ps. The bp240 build is finally bubble free and trimming nicely. Got 3 hours of fairly calm diving in after the testing and tweaking stage. Simple rig but I'm hooked on the satisfaction of having a hand in the assembly process of what I'm diving.

  7. #37
    Chett Lehrer Chett.L has much to be proud of Chett.L has much to be proud of Chett.L has much to be proud of Chett.L has much to be proud of Chett.L has much to be proud of Chett.L has much to be proud of Chett.L has much to be proud of Chett.L has much to be proud of Chett.L has much to be proud of Chett.L has much to be proud of Chett.L has much to be proud of Chett.L'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.
    Yes it's true the Prism Topaz analog secondary is delicate, but with extra care works fine as there are many still out in the field today in use. Robert Landreth who now lives in Spain use to work at steam machine Hermossa beach California, makes a very custom stronger modified version of the analog secondary. I can dig up a picture of this if you would like to see it.

    Best regards,
    Chett. L

  8. #38
    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 Chett.L  View Original Post
    Yes it's true the Prism Topaz analog secondary is delicate, but with extra care works fine as there are many still out in the field today in use. Robert Landreth who now lives in Spain use to work at steam machine Hermossa beach California, makes a very custom stronger modified version of the analog secondary. I can dig up a picture of this if you would like to see it.

    Best regards,
    I would appreciate that.

    Cheers!
    Cameron

  9. #39
    Chett Lehrer Chett.L has much to be proud of Chett.L has much to be proud of Chett.L has much to be proud of Chett.L has much to be proud of Chett.L has much to be proud of Chett.L has much to be proud of Chett.L has much to be proud of Chett.L has much to be proud of Chett.L has much to be proud of Chett.L has much to be proud of Chett.L has much to be proud of Chett.L's Avatar
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    Re: Pondering simplicity: analog o2 monitoring?

    Quote Originally Posted by Sparedone  View Original Post
    I would appreciate that.

    Cheers!
    Cameron
    Enclose is a link to my old Prism Topaz. This is most custom BADASS Prism Topaz ever put together. There are pictures of the tecRB analog secondary made by Robert Landreth for you to look at. This unit is now in Australia owned by a guy that already has two other prism topaz units. If you look very closely you can see how this unit somewhat morphed into the Hollis Prism 2.

    http://www.rebreatherworld.com/showthread.php?32113

    Best regards,
    Last edited by Chett.L; 4th July 2016 at 04:03.
    Chett. L

  10. #40
    Thinker n Tinkerer Sparedone is an unknown quantity at this point Sparedone's Avatar
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    Re: Pondering simplicity: analog o2 monitoring?

    Simply a magnificent build! Love seeing a well thought out rig based on an already excellent design. The immaculate condition in the photos speak volumes as well. You wouldn't happen to have it's twin collecting dust by chance?

    With this inspiration I now have encapsulated strontium aluminate on it's way for glow paint to add to my build.

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