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Par meter with and without water?

Discussion in 'Talk to Tom Barr' started by splash, May 12, 2011.

  1. splash

    splash Lifetime Members
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    I got the Par meter and was wondering if there would be any significant difference if I would measure without water?
    I am finishing up the prototype of the lamp using CREE XM-Ls, while the tank will not be ready for some time. Any advice? Tank is 24x24x48"
     
  2. Gerryd

    Gerryd Plant Guru Team
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    I think the values out of water would be meaningless unless you are growing emersed...

    There is a big difference in values in and out of water...
     
  3. pepetj

    pepetj Lifetime Members
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    Let me add that the difference in measurements with or without water may look negligible when filling a tank with new water for the first time, more so for experimental measurements when a bare bottom tank is used.

    In my planted tanks I get noticeable difference in measurements taken just before a huge water change and once I complete the water change, so assuming one reading represents the actual amount of PPF is, at least in my tanks, an error since it's just a measure at that moment. The log function works well to estimate an average value here.

    I use the leveling plate every time I take measurements; sometimes the air bubble is hard to center.

    Pepetj
    Santo Domingo
     

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