Krypton KH2O problems

Environmental Forum Forums EddyPro Krypton KH2O problems

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This topic contains 3 replies, has 2 voices, and was last updated by  FCO2 5 months, 3 weeks ago.

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  • #10336

    Jucilene
    Participant

    I’m trying to set up the Krypton gas analyser (KH20) and I don’t have any result concerning for measuring water vapor fluctuations. Raw data are in LN(mV), I do have Gain and Offset values. The results of ET (mm/h), water_vapor_density (Kg/m3) and e (Pa) are -9999. Please, could someone help me?
    Thank you very much

    #10337

    FCO2
    Participant

    EddyPro can only do linear conversion for voltages. The millivolt output from the Krypton hygrometer is converted to density (g/m3)
    Here is what I have seen from the manual of the Krypton hygrometer

    Const x = 1 ‘Unique path length of the KH20 [cm].
    Const kw = -0.150 ‘Unique water vapor absorption coefficient [m^3 / (g cm)].
    Const xkw = x*kw ‘Path length times water vapor absorption coefficient [m^3 / g].
    VoltDiff (kh_mV,1,mV5000,1,TRUE,200,250,1,0)
    ln_kh = LOG(kh_mV)
    rho_w = ln_kh/xkw

    if your data file has the ln_kh value, then you need to divide it with xkw, which is unique for each instrument. So in that case, it will be a linear conversion with a slope of 1/xkw and an offset of 0. The output of this conversion will have units of g/m3
    But if the raw H2O data in your file is just mV, then this conversion has to be done outside EddyPro as EddyPro can only do linear conversions.
    Hope this helps

    #10338

    Jucilene
    Participant

    Hi, FCO2
    Thank you very much for your reply.
    In fact , my raw data is LOG (kh_mV) ( natural logaritm LN(kh_mV).
    I have inserted the slope = (-1/0.205) and offset = 8.033. How ever when I look to
    (eddypro_EDDY_essentials_2019-01-23T175227_exp.csv) generated data, I can not see the value water_vapor_density (Kg/m3) , which it is -9999.0

    Thank you,
    Jucilene

    #10340

    FCO2
    Participant

    The issue could be also related to any other setting in your metadata file or project file. I think it would be easier to troubleshoot send your project file, metadata file and a sample data file to envsupport@licor.com and we can get back to you fast.
    Thanks

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