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Thread: Conductivity probe issues after calibration?

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    Conductivity probe issues after calibration?

    Greeting fellow hobbyists,

    I have the PM2 w/ conductivity probe hooked up into my sump. I only have a single temp probe (hooked up to PM1) right next to it in the probe holder with the pH probe. I had finished calibrating the conductivity probe in the 53,000/uS solution, after which I went into the fusion dashboard and the conductivity reading says 25 ppm (while still in the calibration solution?) How's this possible? Shouldn't it read 35?

    Thanks in advance

  2. #2
    Master Control Freak RussM's Avatar
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    My hunch is that you have temperature compensation enabled for the PM2's conductivity probe. In order to use temp comp., you MUST have a temperature probe connected to the PM2.
    Please do not send me PMs with technical questions or requesting assistance - use the forums for Apex help. PM me ONLY if the matter is of a private or personal nature. Thanks.

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    I followed the steps exactly on the BRS how-to video. Meaning, I had set the temp comp to 0.0 during the calibration process, should I hook up the temp probe to the PM2 and remove from the PM1?

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    Frequent Contributor zombie's Avatar
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    Did you let the probe soak for a week or did you just calibrate it immediately? The video doesn't mention this and I just chewed them out for not mentioning it so they can fix their video.

    You might be an engineer if...You have no life and can prove it mathematically.

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    Quote Originally Posted by zombie View Post
    Did you let the probe soak for a week or did you just calibrate it immediately? The video doesn't mention this and I just chewed them out for not mentioning it so they can fix their video.

    You might be an engineer if...You have no life and can prove it mathematically.
    I put the probe in the solution and calibrated within a few mins


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  6. #6
    Frequent Contributor zombie's Avatar
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    That's probably the issue then. The conductivity probe needs to build a hydrated layer before it calibrates and holds the calibration properly. I would order some more calibration fluid (get plenty as the probe needs calibration every 2-3 months) and leave it in your sump til it arrives.

    You might be an engineer if...You have no life and can prove it mathematically.

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    I have spare fluid and my probe is in the sump right now

    Your recommend drying the probe, then leave the probe in the calibration fluid for 1 week then recalibrate?

    The problem with that is that the calibration instructions say that a dry probe needs to settle then the probe in solution needs to settle


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  8. #8
    Frequent Contributor zombie's Avatar
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    No. Leave it in your sump for a week. Then lightly rinse in RO and let dry for like 30 minutes. After that follow the calibration instructions.

    You might be an engineer if...You have no life and can prove it mathematically.

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    That's what I had done (I had gotten my PM2 used and just left it in my sump without calibration)

    I'll try the rinsing in RO next time


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  10. #10
    Frequent Contributor zombie's Avatar
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    Soaking in your sump fills the pores of the glass and coats the outside in a thin layer of fluid that allows the calibration to work correctly and stay correct.

    You might be an engineer if...You have no life and can prove it mathematically.

  11. #11
    Master Control Freak RussM's Avatar
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    Both the "soak it in tank water for a week" and "let it dry for ## minutes or ## hours" are conductivity probe myths which have been perpetuated for years.

    The first one is a twisted transference of the fact that an ORP probe needs about a week to "settle in" & become conditioned, which somehow became erroneously associated with the conductivity probe. For a new conductivity probe, immersion in tank water for several hours or overnight is sufficient to hydrate the new, dry probe. Give it a full day if you want.

    It is not necessary or beneficial to let the conductivity probe dry out. Before doing step 1 of the calibration, rinse well in RO/DI, and gently shake off excess water; gently blot with the tip of a paper towel if you care to. The goal of the rinse and shake is to remove conductive saltwater for the calibration step1 (setting the zero point), and that's it.
    Please do not send me PMs with technical questions or requesting assistance - use the forums for Apex help. PM me ONLY if the matter is of a private or personal nature. Thanks.

  12. #12
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    Quote Originally Posted by RussM View Post
    Both the "soak it in tank water for a week" and "let it dry for ## minutes or ## hours" are conductivity probe myths which have been perpetuated for years.

    The first one is a twisted transference of the fact that an ORP probe needs about a week to "settle in" & become conditioned, which somehow became erroneously associated with the conductivity probe. For a new conductivity probe, immersion in tank water for several hours or overnight is sufficient to hydrate the new, dry probe. Give it a full day if you want.

    It is not necessary or beneficial to let the conductivity probe dry out. Before doing step 1 of the calibration, rinse well in RO/DI, and gently shake off excess water; gently blot with the tip of a paper towel if you care to. The goal of the rinse and shake is to remove conductive saltwater for the calibration step1 (setting the zero point), and that's it.
    Any reason why the dashboard reading is not 35 when the probe is still in the calibration solution?


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