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Thread: Conductivity probe dilemma

  1. #1
    Frequent Visitor mebeknob's Avatar
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    Question Conductivity probe dilemma

    Conductivity probe currently reads ~31.
    I have calibated it automatically with the same result (reads 35 in calibration fluid)
    I have calibrated in manually with 2.2 offset with the same result (reads 34-35 in calibration fluid)

    I have calibrated my refractometer with calibration fluid (35ppm) but that shows the water to be at 35.

    So either my probe is wrong and the water is at 35ppm
    or my refractometer is wrong and the water is at ~31ppm.
    or I've lost my marbles.
    What should I trust?! and what should I do next?

  2. #2
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    Where do you have the probe?
    Micro bubbles can mess with the reading


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  3. #3
    Frequent Contributor zombie's Avatar
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    Did you warm the packet to match tank temp exactly before calibrating? If not, that's why you have a discrepancy.

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    Frequent Visitor mebeknob's Avatar
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    Quote Originally Posted by TheArsalan View Post
    Where do you have the probe?
    Micro bubbles can mess with the reading
    Good point. Although I don't think this is the issue. I previously had the probes in the main display with the same issue. They are currently in the return chamber.

    Quote Originally Posted by zombie View Post
    Did you warm the packet to match tank temp exactly before calibrating? If not, that's why you have a discrepancy.
    I let the packet sit in the aquarium overnight and let the probe dry out overnight as well.

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    Frequent Visitor mebeknob's Avatar
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    Quote Originally Posted by zombie View Post
    Did you warm the packet to match tank temp exactly before calibrating? If not, that's why you have a discrepancy.
    The weirdest part is the probes read @35 in the calibration fluid right after calibrating. Then change once in the saltwater. So this leads me to believe it's a true reading and the saltwater is low.
    But then I check the saltwater with the calibrated refractometer and it shows @35ppm.

    I should take a sample of saltwater to my LFS to verify the reading. This should solve what instrument is telling the truth.

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    Conductivity probe dilemma

    Quote Originally Posted by mebeknob View Post
    I let the packet sit in the aquarium overnight and let the probe dry out overnight as well.

    I could be wrong but I thought these probes arenít supposed to get dried out. Thatís why they come with a moisture/liquid holding cap and thatís how they should be stored.





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    Frequent Visitor mebeknob's Avatar
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    Quote Originally Posted by TheArsalan View Post
    I could be wrong but I thought these probes arenít supposed to get dried out. Thatís why they come with a moisture/liquid holding cap and thatís how they should be stored.
    That is true for the ph and ORP probes.
    You have to dry out the conductivity probe to calibrate it.


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    Master Control Freak RussM's Avatar
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    Quote Originally Posted by mebeknob View Post
    You have to dry out the conductivity probe to calibrate it.
    This is incorrect. Please read this post: https://forum.neptunesystems.com/sho...ll=1#post96587
    I'm not a Neptune support rep. 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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    Frequent Visitor mebeknob's Avatar
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    Quote Originally Posted by RussM View Post
    This is incorrect. Please read this post: https://forum.neptunesystems.com/sho...ll=1#post96587
    Well that's not confusing at all. I'm not using a PM2 module though, rather Terrance's youtube video and the prompted instructions on ApexFusion. They should include this little bit of info "dry it off. It is not necessary to let the probe dry out – just gently shake off excess water and blot the tip with the corner of a paper towel."

    So if you let the conductivity probe truly dry out, does it damage the probe?

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    Frequent Contributor zombie's Avatar
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    Quote Originally Posted by mebeknob View Post
    Well that's not confusing at all. I'm not using a PM2 module though, rather Terrance's youtube video and the prompted instructions on ApexFusion. They should include this little bit of info "dry it off. It is not necessary to let the probe dry out Ė just gently shake off excess water and blot the tip with the corner of a paper towel."

    So if you let the conductivity probe truly dry out, does it damage the probe?
    It wont damage the probe, but it will remove the thin saltwater film that forms on the probe and require it to be soaked for a few hours to reform it. This film can have about a 3ppt effect on the readings.

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    Frequent Visitor mebeknob's Avatar
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    Quote Originally Posted by zombie View Post
    It wont damage the probe, but it will remove the thin saltwater film that forms on the probe and require it to be soaked for a few hours to reform it. This film can have about a 3ppt effect on the readings.
    So the probe has been in the tank all day today and I assume it'll be back to normal.
    What do you recommend I do now?

  12. #12
    Frequent Contributor zombie's Avatar
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    Quote Originally Posted by mebeknob View Post
    So the probe has been in the tank all day today and I assume it'll be back to normal.
    What do you recommend I do now?
    Warm the packet back up, remove the probe and rinse in RODI then pad dry lightly with a paper towel. Do the dry step in manual calibration, then do the wet step. During the wet step it's really easy to get air bubbles so be cognizant of that.

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    Frequent Visitor mebeknob's Avatar
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    Quote Originally Posted by zombie View Post
    Warm the packet back up, remove the probe and rinse in RODI then pad dry lightly with a paper towel. Do the dry step in manual calibration, then do the wet step. During the wet step it's really easy to get air bubbles so be cognizant of that.
    Are these the settings you would use during manual calibration?
    Calibrate.PNG

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    Frequent Contributor zombie's Avatar
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    Quote Originally Posted by mebeknob View Post
    Are these the settings you would use during manual calibration?
    Calibrate.PNG
    The alarms are irrelevant for calibration. I personally don't use them at all and use code in the email alarm instead so I can suppress certain alarms at specific times and customize the delay.

    The TC at 2.2 is a good starting point. It can vary between 1.9 and 2.4 depending on exact tank chemistry, but you can't tell until it has run for at least a few heater cycles.

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    Frequent Visitor mebeknob's Avatar
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    Quote Originally Posted by zombie View Post
    The alarms are irrelevant for calibration. I personally don't use them at all and use code in the email alarm instead so I can suppress certain alarms at specific times and customize the delay.
    Good idea. I might do the same
    Quote Originally Posted by zombie View Post
    The TC at 2.2 is a good starting point. It can vary between 1.9 and 2.4 depending on exact tank chemistry, but you can't tell until it has run for at least a few heater cycles.
    Do I have to re-calibrate if I want to change the TC factor?

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    Frequent Contributor zombie's Avatar
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    Quote Originally Posted by mebeknob View Post
    Good idea. I might do the same


    Do I have to re-calibrate if I want to change the TC factor?
    If the calibration was performed with the tank at exactly 77F, then changing the TC will not change the calibration point. If calibrated at a different temp, changing the TC can skew the readings a small amount, but the amount is small enough, most people dont care.

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    Frequent Visitor mebeknob's Avatar
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    Quote Originally Posted by zombie View Post
    If the calibration was performed with the tank at exactly 77F, then changing the TC will not change the calibration point. If calibrated at a different temp, changing the TC can skew the readings a small amount, but the amount is small enough, most people dont care.

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    So I recalibrated the probe tonight.... first like you said. Same issue. I then did it again a time second with the automatic button. Same issue. In the calibration fluid it reads 35 and in my water it reads 31-32.

    Iím guess since it reads the calibration fluid correctly... my refractomerer has to be off.... or itís just not very accurate.

    Iíll take my water into the LFS tomorrow to check.


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    Quote Originally Posted by mebeknob View Post
    So I recalibrated the probe tonight.... first like you said. Same issue. I then did it again a time second with the automatic button. Same issue. In the calibration fluid it reads 35 and in my water it reads 31-32.

    I’m guess since it reads the calibration fluid correctly... my refractomerer has to be off.... or it’s just not very accurate.

    I’ll take my water into the LFS tomorrow to check.


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    Have you got any refractometer calibration solution? I strongly recommend keeping some on hand. I recently found my refracto calibration was off and I had calibrated mine against my LFS which was reading 1.025 and it turns out it was really about 1.015... So I personally don't trust what the LFS refracto reads...

  19. #19
    Frequent Visitor mebeknob's Avatar
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    Quote Originally Posted by mebeknob View Post
    So I recalibrated the probe tonight.... first like you said. Same issue. I then did it again a time second with the automatic button. Same issue. In the calibration fluid it reads 35 and in my water it reads 31-32.

    Iím guess since it reads the calibration fluid correctly... my refractomerer has to be off.... or itís just not very accurate.

    Iíll take my water into the LFS tomorrow to check.


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    Yeah my first post explains it. But basically either my refractometer (calibrated with 35 fluid) is correct or the salinity probe is correct.... they donít read the same.





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  20. #20
    Frequent Visitor mebeknob's Avatar
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    I noticed a decent amount of buildup inside the probe. Is it okay to put the probe in vinegar for awhile to try and clean off some of the crud?

  21. #21
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    Quote Originally Posted by mebeknob View Post
    I noticed a decent amount of buildup inside the probe. Is it okay to put the probe in vinegar for awhile to try and clean off some of the crud?
    Yes. You can also lightly scrub with a soft bristled toothbrush.

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