Vaisala DMT340 - Manual (Page 180)

User's Guide _______________________________________________________________________
178 __________________________________________________________________ M210704EN-G
Absolute humidity:
T
P
a
w ⋅ =
68 . 216
(3)
Enthalpy:
x x T h
⋅ + ⋅ + ⋅ − =
5 . 2 ) 00189 . 0 01 . 1 ( ) 15 . 273 (
(4)
The water vapour saturation pressure P
ws
is calculated by using two
equations (5 and 6):
∑
=
− = Θ
3
o i
i
i
T C T
(5)
where:
T = temperature in K
Ci = coefficients
C0 = 0.4931358
C1 = -0.46094296 * 10-2
C2 = 0.13746454 * 10-4
C3 = -0.12743214 * 10-7
∑
− =
Θ + Θ =
3
1
4
ln ln
i
i
i ws
b b P
(6)
where:
bi = coefficients
b-1 = -0.58002206 * 104
b0 = 0.13914993 * 101
b1 = -0.48640239 * 10-1
b2 = 0.41764768 * 10-4
b3 = -0.14452093 * 10-7
b4 = 6.5459673