Vaisala HUMICAP HMP41 User's Guide download pdf (Page 87)

Appendix A ______________________________________________________ Calculation Formulas

VAISALA _______________________________________________________________________ 85

APPENDIX A

CALCULATION FORMULAS

This appendix contains the formulas used for the calculated output

quantities.

HMT130 transmitter receives relative humidity and temperature from the

HMP110 probe. From these values dewpoint, frostpoint, absolute

humidity, mixing ratio, enthalpy, wet bulb temperature, saturation vapor

pressure and vapor pressure in normal pressure are calculated using the

following equations.

Symbols:

= Dewpoint temperature (°C)

= Water vapor pressure (hPa)

= Saturation vapor pressure (hPa)

= Relative humidity (%)

= Mixing ratio (g/kg)

= Atmospheric pressure (hPa)

= Absolute humidity (g/m3)

= Temperature (°C)

Tdf

Enthalpy (kJ/kg)

Wet bulb temperature (°C)

Dew/frostpoint temperature (°C)

Dewpoint Temperature

The Dewpoint temperature (Td) of a moist air sample is the temperature

to which the sample must be cooled to reach saturation with respect to

liquid water.

Dewpoint temperature is calculated using:

log























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Vaisala HUMICAP HMP41 User's Guide Page 87