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Total Measurement system error calculation

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  • #48830

    Tierradentro
    Participant

    I need to figure out how much system error is inherant in a pH measurement system. The measurement system is comprised of a pH probe, pH meter and a standard. I am just trying to see if the system is capable of meeting out requirments of +/- 0.01 pH
    Thanks, John

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    #165668

    Chris Seider
    Participant

    You need to do a precision and accuracy study.  You can find many topics on this site.  Let the data speak for itself but I have never a pH probe give a total variation of only +/- 0.01. 
    Don’t forget to include the person using the probe since I’m assuming this is not an in-line system.  People can have an impact on pH readings.
    Good luck.

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    #165681

    Tierradentro
    Participant

    I am trying to prove or disprove the validity of the online water chemistry panels. I was also ask to prove that the standard meter is capable of providing +/- .01 variation.
    Thank You for the response..

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    #165683

    Gary Kellogg
    Participant

    Initially, I would prep for a simple gage R&R using sample solutions  prepped in numbered beakers.  Prep samples ranging from the lowest to highest pH for which you use the system (but not really caring at all what the true pH is for each sample).  Then perform repeated measurements in random order and compare the variation of indicated values within each sample.  The issue could be cross-contamination by the probe, but use your standard probe cleaning method and you will be capturing your systems true measurement variation.   

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