Automated Alkalinity Measurement

Discussion in 'DIY' started by rygh, Jan 27, 2015.

  1. rygh

    rygh Supporting Member

    So as part of designing my water-exchange system, I was thinking about Alk, and
    that it might be possible to integrate a simple ALK measurement device.
    There were others interested, so here it is.

    This is NOT something that does fancy automated titration, and gives you a dKH number.
    (Although I do have some ideas on that also)
    This is simpler. It really just tells you if your ALK has deviated much from a set level.
    But that is what you really need most of the time anyway.

    And a BIG caveat: I have not built and tested it yet, and might never do it. It may not work at all.

    The design is attached as a PDF.

    Water exchange thread here:

    Attached Files:

    jonmos75 likes this.
  2. rygh

    rygh Supporting Member

    Comments welcome, especially if you see a problem.
  3. tygunn

    tygunn Webmaster

    I'm definitely interested in this. So have you figured out the ranges of error at the various stages to get an idea of roughly how close the number you get will be to actual?
  4. rygh

    rygh Supporting Member

    I have not experimented yet, no.
    Main error causes:

    * PH probe drift
    Minimal, since we can compensate by using the first measurement.

    * Inconsistency in Acid solution
    Might need to shake that occasionally.

    * Inconsistency in amount of Acid solution added
    Peristaltic pumps are decent, but far from exact.

    * CO2 effects
    Not sure about that one.

    * Non-linear PH/Alk curves
    If we are not in a fairly and steep part of the curve, a small error can throw
    the measurement off quite a bit.

    I have a lot of things ahead of this in my to-do list, so it will be a while.

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