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An exercise in PH readings - paper VS electronic

stevep Member Posts: 37
I wanted to compare the results of PH paper to an electronic meter to get a better feel for the paper's accuracy in boiler water when the water is contaminated with a dye (Steamaster tablets).

For the test I used the following PH paper that a few others on this board are using:

<a href="http://www.amazon.com/dp/B0045I6IE0/ref=biss_dp_t_asn">http://www.amazon.com/dp/B0045I6IE0/ref=biss_dp_t_asn</a>

The meter I used was this Hanna PH pen:

<a href="http://www.marinedepot.com/Hanna_Instruments_Checker_pH_Pen_Single_Item_Monitors_Controllers_for_Saltwater_Aquariums-Hanna_Instruments-HN1135-FITEMOID-vi.html">http://www.marinedepot.com/Hanna_Instruments_Checker_pH_Pen_Single_Item_Monitors_Controllers_for_Saltwater_Aquariums-Hanna_Instruments-HN1135-FITEMOID-vi.html</a>

When I received the meter it came with a signed certificate of calibration, but I checked it and it was WAY out of calibration. Either the QC person didn't care, or this instrument requires constant calibration; who knows. In any event, the meter calibrated very successfully in both 7.01 and 10.01 buffer solutions so I'm confident the readings I took with it are accurate.

The below pictures should show, in order:

1) Reading taken with PH paper in 7.01 buffer

2) Reading taken with PH paper in 10.01 buffer

3) Reading taken with Hanna meter in 7.01 buffer

4) Reading taken with Hanna meter in 10.01 buffer

The above results told me that the paper is pretty accurate in a buffer solution (calibration solution).

Continuing the pics, in order:

5) Reading taken with PH paper in boiler water

6)Reading taken with Hanna meter in boiler water

The boiler water tested at 8.5 with paper. The boiler water tested at 10.8 with the Hanna meter. I though these results were interesting and figured others on this board might appreciate the info especially considering all the talk of Steamaster tablets lately.


  • Mark N
    Mark N Member Posts: 1,115

    I just gave this a bump because Steam Master tablets are being discussed again. It seems as there may be an issue with getting an accurate reading of boiler water with PH test strips
  • Mike Kusiak_2
    Mike Kusiak_2 Member Posts: 604

    Yes, but which test gives the accurate reading? I don't think that you can automatically assume that the electronic meter's reading is accurate and the test paper is wrong. Both methods seem to give the same reading with calibrated test solutions

    Without some other means of testing to confirm the actual PH reading of the boiler water, all you really know is that the readings don't agree.
  • Mark N
    Mark N Member Posts: 1,115

    Sure would be nice to check the water in an untreated boiler. Is the coloration of the treated water affecting the reading with the test strips?
  • Mike Kusiak_2
    Mike Kusiak_2 Member Posts: 604

    I have  a feeling the dye has very little effect on the paper's accuracy, as the color seems very weak. You could try putting a strip of plain paper into the treated boiler water and see if it stains the paper significantly.

    I have used the PH test paper to check car antifreeze which is sometimes dyed either green or red and the readings do not seem to be be significantly different with either color.
  • Joe V_2
    Joe V_2 Member Posts: 234

    electronics have +\- tolerances that require periodic calibrations. it's the nature of the beast. handling during shipping can knock it out. since you have buffer solutions, you can tweak it back in.

    i use the same model probe to check ph meters in our waste water neutralization system. they are accurate enough. i imagine paper has a shelf life
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