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Thread: Brand new salinity probe inaccurate

  1. #1
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    Brand new salinity probe inaccurate

    I finally got around to setting up my new Apex 2016 and my salinity probe is way off. I have calibrated it three times and it’s still off. I know for a fact my water is 34 ppt (using multiple calibrated refratometers and the digital Milwaukee one too). The probe is reading 41 ppt. Anyway to manually calibrate it?

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    Did you enable temp compensation and float your packet before and during calibration? Did you lightly rinse and pad dry for the dry step or did you try to let it dry for multiple hours like the BRS video says (the BRS video is wrong)?

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  3. #3
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    No I did not, so I follow the instructions on the packet and start up guide and there is more to calibrating the probe?

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    Quote Originally Posted by Heavymman View Post
    No I did not, so I follow the instructions on the packet and start up guide and there is more to calibrating the probe?
    Yes. The instructions don't adequately explain the importance of matching temperature (conductivity is extremely sensitive to temp) and many people confuse what dry really means in the calibration. If the follow the instructions but keep the following in mind, calibration goes much smoother.

    1. Make sure the probe has soaked for at least overnight before calibrating and the values have leveled out (this can sometimes take a few days)

    2. Lightly rinse the probe in RODI and pad dry with a paper towel for the dry step. It should not be completely dry, but it also shouldn't be dripping

    3. The calibration solution must exactly match tank temp or the readings will be skewed. Float the packet for 30 minutes (if you dont do this, error up to 6 ppt is possible) and it's also helpful to make sure the packet is touching water while the value settles (if you don't do this last part, it will only cause about 0.1-0.2 ppt error)

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    Thanks for the help, it just sucks that I have to spend to get new calibration solution.

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    Quote Originally Posted by Heavymman View Post
    Thanks for the help, it just sucks that I have to spend to get new calibration solution.
    If you want to just get the value real close, Randy Holmes Farley has a DIY calibration solution recipe that you can make at home for about a penny worth of table salt. If you don't have a highly accurate digital scale, it will only get you within 1 ppt, but it's a nice stopgap until you get more packets.

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  7. #7
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    Thank you

  8. #8
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    Ok, I strictly followed the instructions. The probe is saying my salinity is 41.1 when it is 34. Could it be the probe because this is getting kind of ridiculous.

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    Quote Originally Posted by Heavymman View Post
    Ok, I strictly followed the instructions. The probe is saying my salinity is 41.1 when it is 34. Could it be the probe because this is getting kind of ridiculous.
    Possibly, but it's usually something else like interference or mistake in calibration procedure.

    Does it read the same in a cup of tank water outside the tank?

    Are you absolutely certain you dislodged all bubbles during the wet step?

    Did the probe read 35 in the calibration solution?

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  10. #10
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    I'm all over the place too. I had to submit a ticket and I'm currently in the process of getting things worked out. For me the dry readings weren't within range (60-90). They recommended that I blow the probe dry with a can of air, and after that didn't work, i'm in the process of restarting my apex and see if that puts the dry side within specs.

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    Yes it reads the same in a cup of tank water.

    As best as I can.

    It has to be the probe, measuring mid 40s in calibration solution.

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    Quote Originally Posted by Heavymman View Post
    Yes it reads the same in a cup of tank water.

    As best as I can.

    It has to be the probe, measuring mid 40s in calibration solution.
    Did you "reset" the probe? If not, unplug the probe and quickly scroll through a manual calibration. There is anecdotal evidence that a reboot after doing this can be helpful as well. It also sounds like there might have been a bubble during your last wet step that didn't get dislodged fully, so taking extra care to ensure they are all dislodged may help.

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    I have reset the probe and I can’t see how I would have not dislodged any bubbles (tapped and flicked the probe). I am beyond frustrated, I submitted a ticket.

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    If it reads mid 40s in calibration solution, it was not calibrated properly.

    After you finish calibrating, leave it in the solution and confirm that it reads 35 or very close to that on the dashboard. You may have to wait a few minutes if doing it from the Fusion dashboard.


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    Thanks, I did that and confirmed it’s not 35 but mid 40s. The probe is not calibrating correctly, it won’t even meet the dry number when trying to do an automatic calibration now.

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    What is the dry reading when doing manual Calibration


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    I believe 772

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    Quote Originally Posted by Heavymman View Post
    I believe 772
    Then you probably didn't plug it back in all the way before you calibrated after the reset. That indicated that your dry and wet reading are almost the same voltage.

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    No I did, double checked. Manual calibrations has always been 772 dry and 691 in calibrations solution. I mean, I don’t think I’m a complete idiot but calibration of this probe shouldn’t be this difficult. I’m very thorough with everything I do, and have done everything to the “t”, as far as suggestions.

    - - - Updated - - -

    I was getting 772 prior to the reset too

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    Quote Originally Posted by Heavymman View Post
    No I did, double checked. Manual calibrations has always been 772 dry and 691 in calibrations solution. I mean, I don’t think I’m a complete idiot but calibration of this probe shouldn’t be this difficult. I’m very thorough with everything I do, and have done everything to the “t”, as far as suggestions.
    You should be getting around 0 dry and around 500-700 wet.

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  21. #21
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    Even when i re calibrated with new solution I am getting 772 dry. I blow dried the probe as well and guess what... 772.

  22. #22
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    reboot the apex, I had to reboot it twice when I was calibrating. first numbers (during calibration) were above the required range, but the second numbers were within range. after rebooting the apex and 2 failed calibration attempts the dry calibration was in range while the wet calibration (in the solution) was below the range.

    Reboot your apex and do the calibration again. you'll probably get it calibrated the first time after reboot.

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