Vaisala DRYCAP DMT340 SERIES, User Manual, Page: 185 / 196

Appendix A ______________________________________________________ Calculation Formulas
VAISALA ______________________________________________________________________ 183
The water vapor pressure is calculated using:
100
ws
w
P
RH P
 
(7)
Parts per million by volume is calculated using:
 
w
w
v
P p
P
ppm

 
6
10
(8)
Symbols:
Td = dewpoint temperature (°C)
Pw = water vapour pressure (hPa)
Pws = water vapour saturation pressure (Pa)
RH = relative humidity (%)
x = mixing ratio (g/kg)
p = atmospheric pressure (hPa)
a
= absolute humidity (g/m3)
T = temperature (K)
h = enthalpy (kJ/kg)