Just calibrated two Refractometers

Discussion in 'Water Chemistry' started by Av8Bluewater, Oct 30, 2013.

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  1. Av8Bluewater

    Av8Bluewater Giant Squid

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    I was wondering if my old cheap ebay refractometer was doing it's job properly so I ordered a new one from BRS. It comes with 1.026 calibration fluid.
    The one from BRS comes with a note taped to the box that says " do not calibrate with RO water".
    So I calibrated it with the fluid and then calibrated it again with RO water to see the results. Turns out that note is there for a reason. When I calibrate it with RO water it will show about two units too high.. (according to the calibration fluid).

    With my old one either method seems to work just fine. Calibrated with RO water then checking with the 1.026 solution it shows 1.026.

    So there you have it.... just a little something to be aware of.
    Buy the way the BRS refractometer will be the one that gets used. Simply because I could never get the other one in perfect focus. This new one is super clear.
     
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  3. Marshall O

    Marshall O Giant Squid

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    Yup, same with mine. I tried calibrating with RO/DI and as you found read 2-3 PPT too high. So I calibrate everytime I use it with 35PPT solution.
     
  4. Renee@LionfishLair

    Renee@LionfishLair 3reef Sponsor

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    Is this what people are doing? Calibrating with RO/DI water?!
     
  5. Marshall O

    Marshall O Giant Squid

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    Far too many unfortunately. I recommend to everyone that they calibrate every time with 35PPT solution. Like I said, I did a test with RO/DI and found it to be off by 2-3PPT. You definitely need to calibrate with the solution closest to what your sample is (i.e. if you wanted to test "clean" water, then I would recommend to calibrate with RO/DI; saltwater - 35PPT all the way).
     
  6. ivanbosk

    ivanbosk Feather Duster

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    My old refractometer clearly states to calibrate with ro/di
     
  7. Marshall O

    Marshall O Giant Squid

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    Keep in mind not all refractometers are made to read the same range. If it says to calibrate with RO/DI, then it was not "made" to read saltwater. Not saying it can't be used as such, but rather that was not the intention. As already stated, no matter what you are measuring, you need to calibrate with solutions closest to what you are measuring. For example, you would never want to calibrate a pH probe to measure saltwater with 4.0 solution.
     
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  9. ivanbosk

    ivanbosk Feather Duster

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    Ok, all i know is it reads accurately.
     
  10. Av8Bluewater

    Av8Bluewater Giant Squid

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    How do you know?
    The only way to know for sure is if you calibrate it with a calibration fluid.
     
  11. Todd_Sails

    Todd_Sails Giant Squid

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    I won't multi quote, was about to.

    Nice thread.

    Was the RO/DI water 0 TDS? If not, it won't read 0.

    This also means you have to assume (and it probably/should be accurate), that the stuff in the bottle is what it says it is- exactly.

    My refractometer has only been done with RO.
    But I had planned soon to compare it to fellow reefers refractometers soon- one's that have the magic calibration fluid.

    I'll try and do it soon and post back on this thread of yours.
     
  12. Av8Bluewater

    Av8Bluewater Giant Squid

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    My RO/DI water is zero TDS. Just got a brand new 6 stage Chloramine plus system from BRS.
    Basically:
    Old Refractometer: Fine using RO water (A little hard to read though since mine is blurry)
    New one: Needs Calibration fluid.