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Humidity definitions and measurement devices

  1. Apr 14, 2015 #1
    I know there are three definitions of humidity. Absolute , relative and specific. Can you tell me if on a typical commercial device (such as the one i have in a clock i have) that measures humidity as percentage is it the relative humidity that it measures? Can the percentage become greater than 100%?
  2. jcsd
  3. Apr 14, 2015 #2


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    When measured as a percentage, its a reference to RH - relative humidity its measuring the relative difference between absolute humidity ( actual water content) and the maximum water content that the air can have at a given temperature

    not that I have ever seen or heard of

    ... in non tropical climates, 100% would usually mean its raining. In tropical climates, I have often seen 95 - 100% and still not raining, but ohhhh gosh, the air is just so unbearable and "sticky"
    Air temperature and pressure have a large bearing on this

    It never ceases to amaze me how much moisture the air can hold as invisible vapour

  4. Apr 14, 2015 #3
    More precisely, it's the ratio of the water vapor partial pressure in the air to the equilibrium vapor pressure of water at the air temperature.

  5. Apr 14, 2015 #4


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    LOL yup .... didn't want to go too deep :wink:
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