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Desigtn schwematic for a ref pH and Kh method for CO2 determination:

Discussion in 'Articles' started by Tom Barr, Oct 18, 2006.

  1. Tom Barr

    Tom Barr Founder
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    View attachment 205

    Here's a simple generalized design for a pH probe and reference KH solution to measure CO2 accurately in an aqurium with tannins, ADA soil, or weird tap water with non bicarbonate alkalinity.

    The larger the tank -ref solution interface/surface area, the faster and better the response times will be.

    Interference with the CO2 mist rising into the catch part of the air gap can produce false positives, but never false negatives.

    This means you will read more CO2 than is truly in solution, rather than the reverse!

    Regards,
    Tom Barr
     
  2. Professor Myers

    Professor Myers Guru Class Expert

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    Ya Tease !

    Where's the Illustration ? :confused:
     
  3. Tom Barr

    Tom Barr Founder
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    click on the file

    Regards,
    Tom Barr
     
  4. Professor Myers

    Professor Myers Guru Class Expert

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    Nada ???

    Click-ed File. I see words without illustration ? Wonder if my word program is shhcrewwy ? :( No Joy...
     
  5. Tom Barr

    Tom Barr Founder
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    PHP:
    C:\Documents and Settings\Tom\Local Settings\Temporary Internet Files\Content.MSO\WordWebPagePreview\5819B506.mht
     
  6. turbomkt

    turbomkt Lifetime Charter Member
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    Tom,
    I've got a modification to your schematic that may appeal to those who want less to show up in their tanks. Specifically, make this to hang over the edge of the tank like a HOB filter or overflow. Something like this (CD-790065 at DrsFosterSmith.com) should give an idea of what I'm talking about.

    The reference solution and probe can be outside the tank, while only a little would reach inside.
     
  7. David Hui

    David Hui Lifetime Charter Member
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    Tom,

    Where is the water sample measure? I don't get it.

    Thanks

    David
     
  8. VaughnH

    VaughnH Lifetime Charter Member
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    No, you don't want the reference solution and probe outside the tank. Unless the reference solution is at the same temperature as the tank water at all times there will be distillation going on, with water moving from the warmer water to the colder water. That would alter the KH of the reference solution. Much better to just minimize the size of the unit in the water.
     
  9. VaughnH

    VaughnH Lifetime Charter Member
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    Tom, it is likely to take more than a grommet to adequately seal the point where the probe enters the drop checker. That connection has to be air tight, or the device doesn't work. Something more like the sealing nuts used for wires going into a sealed device would be best. And, given the relatively short life of the probes, you can't just use silicone sealant to seal it. I think the best design would be made from two sizes of acrylic pipe - the inner one about twice the diameter of the probe, the outer one about twice the diameter of the inner one, and the inner one with a bottom piece that extends to attach the two together. At the top would be a solid piece of acrylic with a liquid tight pass thru fitting from Heyco, Handles, Thumb Screws Captive Panel Screws, Stand offs, Handles, Connector Hardware, Lyn-Tron, Inc. - Spacers, Thumb Screws, Captive Panel Screws, Standoffs, Handles, Connector Hardware - Bolt Products Inc., Fasteners, Cable Ties, Distributor Standar, which fits the probe diameter.

    [​IMG]
     
  10. Tom Barr

    Tom Barr Founder
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    Vaughn,

    I have 500 grommets that are rated at 30 psi sittng here, they are very air tight!:D

    I used them on the CO2 reactors I use to make.

    They fit the probe nicely.
    I'll make on and show folks how to with some pics.

    Regards,
    Tom Barr
     
  11. VaughnH

    VaughnH Lifetime Charter Member
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    That should be a very interesting DIY project. I personally prefer the colored water approach, but for those with color vision problems or a desire for more precise numbers this would be ideal. I'm assuming the grommets are a donut with a slit around the outside to grip the "sheet metal" they go thru, and an undersized hole in the middle to grip the probe? That would be much cheaper and simpler than the Heyco devices, so it sounds great. You can make 500 of these devices now and make a million bucks on ebay!
     
  12. Tom Barr

    Tom Barr Founder
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    The Viewtainers have a good rubber seal that's good enough for the reactors, and they cheap, 1.99$ easily melted and formed with a lighter etc, a suspended cap is all that needs to be added.

    They(Viewtainer) also make smaller ones so you can add one inside the other etc.

    No need for a grommet, but if you wanted to make a nice heavy duty pH measurement checker out of Acrylic, which is a material I most often tend to think with, I would have a use for them thar grommets:)

    I might make a nice acrylic version for a client etc.
    I'll also need to make them 5 liters of Reference solution also:)


    Regards,
    Tom Barr
     
  13. Tom Barr

    Tom Barr Founder
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    Doh!

    a simple U shape and a PCV or acrylic tubing bent in a U shape with a cap on one end.


    IIIIII
    III III
    III III

    The capped end would have the ref solution, the other open to the tank.

    You'd just leave an air gap on the top of the U.
    You do not need to see the solution other than to make sure it's there etc and add a pH probe to this.

    They already make pH in line probe assemblies.

    A 1" PCV elbow(the one's with the flat end, not curved) and a grommet would likely work well.

    Regards,
    Tom Barr
     
  14. Professor Myers

    Professor Myers Guru Class Expert

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    Good Stuff !

    This and VaughnH's orginal thread are really good stuff fellas ! :)
     
  15. turbomkt

    turbomkt Lifetime Charter Member
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    Makes sense. Thanks!
     
  16. yme

    yme Lifetime Charter Member
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    great stuff guys!

    I placed a link to this thread at a dutch aquarium forum: Veni Vidi Vissie :: Begin.
    everybody should know this!


    greetz,

    yme
     
  17. VaughnH

    VaughnH Lifetime Charter Member
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    A PVC tee and a PVC elbow, joined at the side outlet of the tee would also work, with a cap on the bottom outlet of the tee, and the probe entering the top outlet of the tee. The elbow would point down into the water to establish the air gap. About $1 worth of fittings. Getting the probe sealed where it enters the tee would be the only mildly hard part.
     
  18. IUnknown

    IUnknown Lifetime Members

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  19. VaughnH

    VaughnH Lifetime Charter Member
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    The way I would modify that DIY controller is to nod my head knowingly, then do a google search for a cheap pH monitor. I know a bit about electronics, but not enough to tackle that. The way I have modified meters before is to add another scale to them that reads the correct values, but that only works with analog meters.
     
  20. VaughnH

    VaughnH Lifetime Charter Member
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    Have you had a chance to prototype this yet? This could be the ultimate CO2 checker. You need to keep the pH probe wet all of the time anyway, so this could act as storage device for the probe too - just remove it from the tank water and leave it in a small cup of other water. This will also cure acne, hives, and lumbago, and accurately forecast the weather! Really. (Maybe I need to reduce my meds?)
     

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