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Thread: Who do you believe? Refractometer or Conductivity probe?

  1. #1
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    Who do you believe? Refractometer or Conductivity probe?

    So my conductivity probe readings are all over the place. I've calibrated it multiple times (With the solution the same temperature as water) and it reads correct in the calibration solution. Out of the solution and in the tank the salinity swings from 32.5 to 35. But typically swings 32.5 to 33.

    When I double check it with my $20 refractometer it reads 1.026 each time no mater what the conductivity probe says. The refractometer has also been calibrated multiple times.

    So which do I trust? All inhabitants seem to be doing perfect. But the difference 1.022 and 1.026 seems out of the norm.

  2. #2
    Frequent Contributor zombie's Avatar
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    Did you enable temp compensation?

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

  3. #3
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    I have. 2.2 %. Shouldn't that also reflect in any refractometer reading I do?

  4. #4
    Frequent Contributor zombie's Avatar
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    Did you calibrate the refractometer with calibration fluid or zero with RO?

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

  5. #5
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    I've done it with both actually...

  6. #6
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    Is the cable for your probe separated from any power cords?

  7. #7
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    Yes it is

  8. #8
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    How did the calibration worked out? Or still the same?


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  9. #9
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    Hasn't. The probe is still way off.

    Quote Originally Posted by basonder14 View Post
    How did the calibration worked out? Or still the same?


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  10. #10
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    Quote Originally Posted by mtordie View Post
    Hasn't. The probe is still way off.
    Do you think that your probe died or any others ideas?


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  11. #11
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    The probe is still good considering it will still read the calibration fluid. Other then that I am out of ideas...

  12. #12
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    Your typical swing of 32.5 to 33 translates to 1.0245 to 1.0249.

    That is within 0.001 sg. Your refractometer cannot measure to that resolution.

    As to the difference in reading, it is mostly likely due to the difference in the way both Instruments measure Salinity.


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  13. #13
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    32.5 at 78 degrees does not equal 1.025 that shows on the refractometer regardless of when I test it. Likewise it shows 37 right now at 78 degrees. Yet the refractometer that has been calibrated shows 1.025. Either way its still a couple thousands off but a couple thousands I can deal with. Still would be nice for it to be more accurate then a refractometer.

  14. #14
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    Just to clarify, are you saying the scale on the refractometer does not show that 32.5 = 1.025 or that the water @ 32.5 as measured by the probe does not read 1.025 on the refractometer?

    Is the change in reading cyclic?

    If you overlay the temp graph over the probe graph, do they correlate?

    Are you logging all your outlets?

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