Vaisala HMP155 User Manual download pdf (Page 81)

Appendix A ______________________________________________________ Calculation Formulas

VAISALA _______________________________________________________________________ 79

APPENDIX A

CALCULATION FORMULAS

This Appendix contains the formulas used for the calculated output

quantities.

The HMP155 series probe measures relative humidity and temperature.

From these values dew point and frost point, mixing ratio, wet bulb

temperature, absolute humidity and enthalpy in normal pressure are

calculated using the following equations:

Dew point/frost point:

15.273

1078.6

log

5.7

3.237































(1)

is the water vapor pressure. Dew point/frost point is measured in

Kelvin.

Mixing ratio:

99.621 

(2)

Absolute humidity:



(3)

where

= 216.679

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Vaisala HMP155 User Manual Page 81