Vaisala HMT130 - Manual (Page 91)

Appendix A _______________________________________________________ Calculation Formulas
VAISALA ________________________________________________________________________ 89
Water Vapor Pressure
Vapor pressure refers to the vapor pressure of water in air or other gas.
Water vapor has a partial pressure Pw which is part of the total pressure
of the gas.
The water vapor pressure is calculated using:
100
ws
w
P
RH P ⋅ =
[ ]
hPa
(8)
Accuracies of Calculated Variables
Accuracies of the calculated variables depend on the calibration accuracy
of the humidity and temperature sensors; here the accuracies are given
for ± 2 %RH and ± 0.2 °C.
Accuracy of Dewpoint Temperature °C
Relative humidity
Temp. 10 20 30 40 50 60 70 80 90 100
-40 1.86 1.03 0.76 0.63 0.55 0.50 0.46 0.43 — —
-20 2.18 1.19 0.88 0.72 0.62 0.56 0.51 0.48 — —
0 2.51 1.37 1.00 0.81 0.70 0.63 0.57 0.53 0.50 0.48
20 2.87 1.56 1.13 0.92 0.79 0.70 0.64 0.59 0.55 0.53
40 3.24 1.76 1.27 1.03 0.88 0.78 0.71 0.65 0.61 0.58
60 3.60 1.96 1.42 1.14 0.97 0.86 0.78 0.72 0.67 0.64
80 4.01 2.18 1.58 1.27 1.08 0.95 0.86 0.79 0.74 0.70
100 4.42 2.41 1.74 1.40 1.19 1.05 0.95 0.87 0.81 0.76
120 4.86 2.66 1.92 1.54 1.31 1.16 1.04 0.96 0.89 0.84
140 5.31 2.91 2.10 1.69 1.44 1.26 1.14 1.05 0.97 0.91
160 5.80 3.18 2.30 1.85 1.57 1.38 1.24 1.14 1.06 0.99
Accuracy of Mixing Ratio g/kg (Ambient
Pressure 1013 mbar)
Relative humidity
Temp. 10 20 30 40 50 60 70 80 90 100
-40 0.003 0.003 0.003 0.003 0.003 0.004 0.004 0.004 — —
-20 0.017 0.018 0.019 0.021 0.022 0.023 0.025 0.026 — —
0 0.08 0.09 0.09 0.10 0.10 0.11 0.11 0.12 0.13 0.13
20 0.31 0.33 0.35 0.37 0.39 0.41 0.43 0.45 0.47 0.49
40 0.97 1.03 1.10 1.17 1.24 1.31 1.38 1.46 1.54 1.62
60 2.68 2.91 3.16 3.43 3.72 4.04 4.38 4.75 5.15 5.58
80 6.73 7.73 8.92 10.34 12.05 14.14 16.71 19.92 24.01 29.29
100 16.26 21.34 28.89 40.75 60.86 98.85 183.66 438.56 — —
120 40.83 74.66 172.36 — — — — — — —