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Thread: pH meter issues . . .

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    BigBella's Avatar
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    pH meter issues . . .

    To those of you familiar with pH meters, I would like to pose an odd question. For some reason, I have recently had some difficulty in calibrating my HM Digital pH-200 meter with any of the testing solutions. When I attempted it, I could not manually calibrate the numbers by a long shot -- 4.01; 7.0; 10 -- even though I have tried different batches of the solutions, as well as different brands; have also figured in the temperature differences in terms of pH; and even the auto-calibration function is miles off.

    The probe itself is undamaged and the tip had been replaced within the last year. To further confuse things, when I placed the probe in distilled water, it registered an an ideal pH 7.0 at 20˚ C -- exactly what to expect from distilled or deionized water . . .
    “Sì perché l'autorità dell'opinione di mille nelle scienze non val per una scintilla di ragione di un solo . . ."

    -- Galileo "Biff" Galilei

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    kulamauiman's Avatar
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    electrode going funky. might have some mineral deposits on them. I actually remember doing rinses in distilled water and sanding things in the old days

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    BigBella's Avatar
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    Quote Originally Posted by kulamauiman View Post
    electrode going funky. might have some mineral deposits on them. I actually remember doing rinses in distilled water and sanding things in the old days
    Mach, I thought so too; but even with a powerful loupe, there is absolutely no trace of any deposit to be seen; and I religiously rinsed the probe in distilled or deionized water after each use . . .
    “Sì perché l'autorità dell'opinione di mille nelle scienze non val per una scintilla di ragione di un solo . . ."

    -- Galileo "Biff" Galilei

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    kulamauiman's Avatar
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    battery going bad? internal hardware issue with corrosion?


    in the distilled water try take a reading swirling it around

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    BigBella's Avatar
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    Quote Originally Posted by kulamauiman View Post
    battery going bad? internal hardware issue with corrosion?


    in the distilled water try take a reading swirling it around
    Battery indication is fine; so too the display, so I don't expect internal corrosion. When swirling in distilled water, it drops into the pH 5.4-5.6 range, then settles to 7.0 or 7.01 after a minute or so . . .
    “Sì perché l'autorità dell'opinione di mille nelle scienze non val per una scintilla di ragione di un solo . . ."

    -- Galileo "Biff" Galilei

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    Formerly known as Pineapple Nepenthesis's Avatar
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    Not to derail the thread, but I was going to get a cheapo pH meter to test the pH of my nep soil and I didn't want to get a bum one... What is the best brand?

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    BigBella's Avatar
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    Quote Originally Posted by Pineapple View Post
    Not to derail the thread, but I was going to get a cheapo pH meter to test the pH of my nep soil and I didn't want to get a bum one... What is the best brand?
    It is difficult to get a reliable pH reading from compost, since the probes basically measure hydrogen ion concentration in solutions. You're far better off getting a ballpark figure of the pH from the leachate in your drainage trays.

    There are many on the market, but I would suggest one that allows push-button calibration over those that require a screwdriver . . .
    Last edited by BigBella; 05-16-2012 at 08:02 PM.
    “Sì perché l'autorità dell'opinione di mille nelle scienze non val per una scintilla di ragione di un solo . . ."

    -- Galileo "Biff" Galilei

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    Hello, I must be going... Not a Number's Avatar
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    Back in the college lab days the probe on the pH meters we used had to be kept wet at all times in a storage solution when not in use. Letting them dry out meant ruining the probe. No idea with current units.
    Grand Hotel... always the same. People come, people go. Nothing ever happens.

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