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Thema: Conductivity Probe values drifting down

  1. #1
    Registriert seit
    20.02.2017
    Beiträge
    4

    Standard 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
    Registriert seit
    08.11.2016
    Beiträge
    8

    Standard

    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
    Registriert seit
    20.02.2017
    Beiträge
    4

    Standard

    Zitat Zitat von clumeng Beitrag anzeigen
    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
    Registriert seit
    23.10.2016
    Beiträge
    48

    Standard

    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
    Registriert seit
    21.02.2017
    Beiträge
    18

    Standard

    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
    Registriert seit
    19.02.2017
    Beiträge
    17

    Standard

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

  7. #7
    Registriert seit
    18.02.2009
    Ort
    Kaiserslautern
    Beiträge
    7.064

    Standard

    Hi

    I can't find any errors in our test systems in regards to salinity. We also have meanwhile several hundred of new P4 owners, I doubt that there is a system error.
    The values in our test systems are plausible and without significant drifting.

    The hardware and firmware parts of the conductivity measurement (incl. temp. compensation) are practically the same as found in the P3, and the P3 is working fine for over 9 years now ...

    The conductivity measurement is extremely depending on a correct temperature measurement for the compensation, maybe there is the reason.

    The temp. during the calibration must be 100% correct (best way to do so: have the calibration fluid bottle floating in your tank for a few hours so it has the same temp. as the tank water).

    Later the cond. probe must be very close to the temp. probe during operation.

    Maybe calibrate again.


    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 have no logical explanation for this. The probe just measures the resistance of the water between 2 electrodes, nothing else.
    If you remove the probe out of the tank the probe temp. will change.

    Or maybe moving the probe eliminated coincidentally the real problem, like air, algaes, snails, ...
    No support or warranty issues over PM! Please send PMs to the moderators only if you have general problems with using the forum! Thanks for helping us to keep the support efficient.
    Kein Support oder Reklamationsabwicklung über PM! Bitte senden Sie an die Moderatoren nur PMs bei allgemeinen Problemen mit der Verwendung des Forums! Danke dass Sie uns dabei helfen, den Support effektiv zu gestalten.

  8. #8
    Registriert seit
    19.02.2017
    Beiträge
    17

    Standard

    i will do another calibration tonight with method of floating bottles.. but i have 23 C in tank.. must setup this temp on calibration request?? (standard set at 25 for reference solution)

  9. #9
    Registriert seit
    18.02.2009
    Ort
    Kaiserslautern
    Beiträge
    7.064

    Standard

    you must enter the temp. your fluid has in the moment of the calibration
    No support or warranty issues over PM! Please send PMs to the moderators only if you have general problems with using the forum! Thanks for helping us to keep the support efficient.
    Kein Support oder Reklamationsabwicklung über PM! Bitte senden Sie an die Moderatoren nur PMs bei allgemeinen Problemen mit der Verwendung des Forums! Danke dass Sie uns dabei helfen, den Support effektiv zu gestalten.

  10. #10
    Registriert seit
    19.02.2017
    Beiträge
    17

    Standard

    yes yesterday i do with my own digital thermometer .. but also today swirl down around 0.5 psu ..

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