Calculate Saturation and Actual Vapour Pressures (SVP). All calculations assume Temp (t) in Celcius


1)    Saturation VP = 6.11*10^((7.5t)/(t+237.3))
          i.e. SVP for (t) at 10.0 degC = 12.283mb


2)    Actual Vapour Pressure (VP) can now be calculated 
      using the (RH) reading
                Actual VP = (SVP*RH)/100


3)    Calculate Dewpoint Temperature for current RH value

      => dewpoint temp = 237.3A/ (7.5 - A)
      A = log10 (AVP / 6.11)