Refractometer Calibration

Discussion in 'Test Kits, Controllers, Reactors and Dosers' started by Warr7207, 22 Feb 2008.

  1. Warr7207

    Warr7207

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    Forgotten how to calibrate my Refractometer. It had something to do with a certain amount of RO water and salt. Please help.
     
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  3. Rod

    Rod

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    Refractometer

    This may help.
     
    Last edited: 27 Feb 2009
  4. Alan

    Alan Admin MASA Contributor

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    Warren if i am not mistaken you use RO/DI to get it to the bottom reading ie 0. May be wrong here as i have never done it.
     
  5. Tobes

    Tobes Retired Moderator

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    Warr, you take a few drops of RO/DI and put it on the prism - no salt - close and look into it. Adjust it till back at 0 (small screw on top). Suck up tank water and test - accurate reading.
    I calibrate mine everytime before I measure my tank and the make-up water - just to be safe. I rinse the prism with the new water to be tested by holding the refractometer with the prism facing down and slow squirt water over prism and tilting glass - just to get rid of dust and/or drops from "other" water and so my readings aren't affected. I sometimes calibrate, test tank water and then make-up water all after each other. :wave2:
     
  6. Warr7207

    Warr7207 Thread Starter

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    Thanks Rod, I now have a manual :thumbup:
     
  7. Warr7207

    Warr7207 Thread Starter

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    Guys I only have a reading of 1 as the lowest. Is this a mistake on your part or does my Refractometer have a digit missing ?
     
  8. Geordie

    Geordie

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    the very bottom line should show

    specific gravity 1.000................ ppm 0

    Calibrate it to this line mate
     
  9. Warr7207

    Warr7207 Thread Starter

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    Have those 2 numbers, cool
     
  10. Rory

    Rory Admin MASA Contributor

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    Calibration so that RO or RO/DI or distilled water = 0 is one way to calibrate but not the best because the refractometer could still be a bit out if say 1ppm shows as 1.1ppm, by the time you're looking at 35 ppm it will show as 38.5ppm. The better way to calibrate is using a sample with a known ppm around the range you would usually be testing at, ie 35 or so. This is why the "experts" calibrate with a mixture of known quantities rather than at 0.
     
  11. Warr7207

    Warr7207 Thread Starter

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    That sounds like what I was originally told. But what is the measurements of the mixture that needs to be made up?
     
  12. Rory

    Rory Admin MASA Contributor

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    35 parts salt and 999965 parts water...
     
  13. Rory

    Rory Admin MASA Contributor

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    You will need a rather accurate scale. Look at what it says you must mix the salt to on the packet/box/bucket, ie. 35g per liter or something then do that really accurately, mix properly and test.
     
  14. Warr7207

    Warr7207 Thread Starter

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    I'll try it out
     
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