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Thread: Conductivity Probe values drifting down

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  1. #1
    Join Date
    21.02.2017
    Posts
    7

    Default Conductivity Probe values drifting down

    I have set up the Profilux 4 to monitor conductivity with a goal of 53mS. I have it assigned temperature compensation as "Temperature 1". I have ATO with Tunze and Temp stable at 26 degrees. When I set up the probe the conductivity reads 53.2 and slowly drops over a day or two to where it is now 52mS. I have checked the aquarium (Reefer XL 450) for leaks and it is intact. I haver looked for salt creep and find none.
    I therefore am concluding that there is an issue with the probe or software reading it. Can I get assistance with this?

  2. #2
    Join Date
    08.11.2016
    Posts
    8

    Default

    Conductivity should be roughly proportional to salinity so you need to check this with a calibrated refractometer. That being said I think that it's mainly useful for trends - meaning that my tank will have a different conductivity than yours even with the same s.g.

    My tank is stable at 60.5mS with SG of 1.026 with a calibrated refractometer. I noticed it creep up to 61.3 over a day or so and found that my ATO was set a bit low and SG had crept up to 1.028. Later after a 10% water change my conductivity changed to the 61 range at the same S.G.

  3. #3
    Join Date
    21.02.2017
    Posts
    7

    Default

    Quote Originally Posted by clumeng View Post
    Conductivity should be roughly proportional to salinity so you need to check this with a calibrated refractometer. That being said I think that it's mainly useful for trends - meaning that my tank will have a different conductivity than yours even with the same s.g.

    My tank is stable at 60.5mS with SG of 1.026 with a calibrated refractometer. I noticed it creep up to 61.3 over a day or so and found that my ATO was set a bit low and SG had crept up to 1.028. Later after a 10% water change my conductivity changed to the 61 range at the same S.G.
    I really appreciate that you are trying to help but I think that the temperature corrected calibration fluid should be the most scientific way to calibrate a brand new probe. The refractometer is not temperature corrected and may itself be in error. I believe that something is happening to the probe but I don't know what. When I lift it out of the water and shake it and place it back in, the level goes back up. I have it placed in an area of high current aw2ay from air bubbles. and my ATO keeps the s.g. extremely stable.

    I really would;d like to hear from the company on this and may have to go directly to support. I thought that this was the appropriate way to get help from them but perhaps it is not.

  4. #4
    Join Date
    23.10.2016
    Posts
    55

    Default

    I have the same issue.
    My ATO is stable, my salt level also.
    I messured over years with an IKS Aquastar and IKS platin probe without the effect of down drifting conductivity.
    As I got the brand new PL4 set, I followed the calibration instructions and compared the result with the old IKS platin probe messures. It was nearly the same.
    After a few days, sometimes hours - the conductivity level drops drifts down a lot.
    Also I have place both probes in the same holder to test if there is an issue with the GHL probe.
    The IKS probe stays stable and the GHL probe drifts down after 1-3 days. If i shake the GHL probe - both levels are the same.
    There are no air bubbles, algae or something else near to the probes.
    If needed, I can shoot some comparism pictures of both computers and their measurements.

    Whats the cause for that? I also add an extra shielding (alluminium) for testing without any effects...

  5. #5
    Join Date
    21.02.2017
    Posts
    24

    Default

    It's a bug in the system. It must be. I'm having the exact same issue. You can "reset" the downward drifting by pulling the conductivity probe out of the water for a second and putting it back in. When I do this, it resets the downward drifting effect.

    I calibrated my brand new conductivity probe correctly (floating the 50 ms solution to equal the right temp) and when I initially put the probe in the tank, it reads correctly (matching with my freshly calibrated refractometer).
    Over the course of about 12 hours, the salinity slowly drifts downward on the conductivity probe. I rechecked the measurement with the refractometer and everything was exactly the same.
    I recalibrated the probe and put it back in, it now matched the refractometer again perfectly.
    Over the course of 12 hours, the probe again drifted downward, from about 1.0265 to 1.0235 (a pretty big downward drift).
    I pulled the probe out of the water for a second and put it back in. It now reads correctly, but I'm assuming it's going to drift downward again.

    Definitely either a batch of defective sensors or defective software.

  6. #6
    Join Date
    19.02.2017
    Posts
    18

    Default

    i also notice this thing.. same issues with my PL4

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