Additional tests for colorimeter (pH, alkalinity, calcium hardness, etc.)

  • @briansone

    Are you willing to share the API results (bromothymol blue)?

    I have pH calibration for API pH 6.0-7.6 and API High Range pH 7.4 to 8.8. The curves are non-linear (polynomial), especially for the high range. I am new to IO Rodeo Forum and I am wondering if there are discussions regarding non-linear calibrations (I looked and didn't find any).

    Here's our calibration:
    Colorimeter Data
    K.Jin, A.Aufdenkampe, B.Fisher
    LED red
    API pH 6.0-7.6 bromothymol blue
    pH | Absorbance
    5.8 0.00
    6.0 0.02
    6.4 0.07
    6.8 0.24
    7.2 0.40
    7.6 0.56
    7.8 0.65
    8.0 0.69

  • @fisherba

    I imported your data into the colorimeter-plot program and tried looking at a couple a nonlinear calibrations. The 4-th order polynomial fit looks pretty reasonable.

    nonlinear fit

  • Thanks @Will-Dickson! I also just discovered that I have to select the fit type before plotting and it all works. Doing this should help @briansone get around the issue of the plot trying to intercept with (0,0).

  • @Will-Dickson

    Hmm... the colorimeter software won't let me fit beyond 3rd order.

    pH curve screen shot

  • @fisherba

    Any error message? or are the radio buttons disabled?

  • @Will-Dickson

    There isn't an error message. When I select 4th order and hit the plot button, nothing happens. But I choose linear, 2nd order, or 3rd order it works fine. Same data I posted, same that you used. I'm using that Mac OS software version 4, which appeared to be the current version when I looked yesterday.

    (Thanks so much for your responsiveness!)

  • @fisherba

    Yes I think you are getting hit with a bug in the nonlinear fitting which I fixed on (2016-09-04).

    The fix is in the source in the repository (, but I don't think I have packaged up new stand alone versions for Mac or Windows since the fix.

    I'll try to put together some new standalone versions this weekend.

  • Hi @Will-Dickson, I haven't noticed a bitbucket update in the downloads, and I'm afraid I don't have sufficient Python experience to update it myself. Keep me posted and I look forward using the updated version. Thanks!

  • @fisherba

    Sorry about the delay. I've put new versions of colorimeter software (colorimeter-v05) for Windows and Mac OS here Let me know if you have any issues.

  • @Will-Dickson Thank you! I very much appreciate your help!

  • Is there any changelog available ?

  • @poseidon

    I don't have a change log, but this is probably something I should start doing. There are the repository commits here The new release incorporates all the changes starting at 2016-09-04

  • @Will-Dickson Hi. We bought io rodeo colorimeter kit last week and we downloaded your new software which is the version 5. We seem to have a problem. When we click the start button of the measurement program, the program exits. But we don't find this issue when using the version 4 software. I am using a Windows 10 OS.

  • @aleyah

    I can reproduce the issue you are seeing. I will look into it this week and see if I can fix the problem.

  • This post is deleted!

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