Pp p ppm – Vaisala HMT330 User Manual
Page 199
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Appendix B _______________________________________________________ Calculation Formulas
VAISALA _______________________________________________________________________ 197
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:
T
d
=
dewpoint temperature (°C)
P
w
=
water vapor pressure (hPa)
P
ws
=
water vapor 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)
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