Vaisala DM500 - Manual (Page 132)

User's Guide ______________________________________________________________________
130 _________________________________________________________________ M210205EN-D
in air at that particular temperature. It is defined below as the ratio of
the water vapor pressure P
w
to the saturation water vapor pressure P
ws
.
% 100 / ⋅ =
ws w
P P RH (4)
Air temperature (ºC) Dewpoint temperature (ºC)
0 10 20 30 40 50 60 70 80 90 100
100
80
60
40
20
0
-20
-40
160
140
120
100
80
60
40
20
0
-20
-40
Relative humidity (%RH)
Figure 26 Water Vapor Saturation Curves
Mixing Ratio (x)
Mixing ratio (x) is mass of water vapour per unit mass of dry air with
which it is associated.
w tot
w
P P
P
x
-
9907 . 621 ⋅ = (5)
where
P
w
= water vapor pressure (Pa)
P
tot
= total process pressure (Pa)