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Thread: Calibration trouble (2nd probe) - Hanna HI 98129 - Am I doing something wrong?

  1. #1
    Join Date
    Jul 2011
    Posts
    3

    Default Calibration trouble (2nd probe) - Hanna HI 98129 - Am I doing something wrong?

    Hi everyone,

    I'm on my second HI 98129 combo probe (from Amazon) after thinking the first one was defective. How I'm wondering if I have a second bad probe... here's why:

    1. Received probe - soaked overnight in HI 70300 storage solution
    2. Rinsed with clean distilled water
    3. Pulled up 2 point calibration mode
    4. Waited for stabilization icon (little clock) to disappear
    5. calibrated with 7.01 and waited for 4.01 prompt
    6. rinse in clean distilled water again
    7. calibrated with 4.01
    8. LCD says 'OK' and goes directly to pH monitoring mode and begins measuring the 4.01 solution it's already in - reading starts diving down and keeps going well past 3.5 after several minutes

    So I'm thinking I just need to 'reboot' the thing and try again so....

    1. Turn off and back on
    2. in pH mode, wait for stabilization icon to go away
    3. measure 4.01 again - stabilization icon comes back on like I expect it should do, but when the reading reaches roughly 3.85 the clock goes away but the reading keeps going down until it again reaches somewhere around 3.5 and then shuts off on its own (again several minutes)

    Am I screwing this up or is something else amiss?

    I had similar results with the 1st meter I returned - which seems a bit odd.

    The buffer solutions were purchased a few weeks ago with the seal intact (Flora Hydroponics brand)... I know its a possibility these could be trash but looking for some other ideas before I go out and buy more.

  2. #2
    Join Date
    Aug 2011
    Location
    Ohio
    Posts
    22

    Default

    Here is an awesome article from max yield about pH and EC probe care, also from what I understand you are never supposed to use Distilled water on pH probes.
    http://www.maximumyield.com/article_...eatureVar=true

  3. #3
    Join Date
    Jul 2011
    Posts
    19

    Default

    It's OK to rinse the electrodes with distilled or RO water, in fact, that is standard laboratory practice between samples. You just don't want to leave a probe soaking in distilled water for the reasons mentioned in the maximumyield article.

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