Prh p, Pp p ppm – Vaisala DMT340 User Manual
Page 181
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Appendix A _______________________________________________________ Calculation Formulas
VAISALA _______________________________________________________________________ 179
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)
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