Vaisala DRYCAP DMT340 SERIES Betriebsanweisung PDF herunterladen (Seite 165)

Appendix A ______________________________________________________ Calculation Formulas

VAISALA ______________________________________________________________________ 165

APPENDIX A

CALCULATION FORMULAS

This Appendix contains the formulas used for the calculated output

quantities.

The DMT340 series transmitters measure relative humidity and

temperature. From these values dewpoint, mixing ratio, absolute

humidity and enthalpy in normal pressure are calculated using the

following equations:

Dewpoint:

log

















(1)

is the water vapor pressure. The parameters A, m, and Tn depend on

temperature according to the following table:

t A m Tn

<0 °C * 6.1134 9.7911 273.47

0 ... 50 °C 6.1078 7.5000 237.3

50 ... 100 °C 5.9987 7.3313 229.1

100 ... 150 °C 5.8493 7.2756 225.0

150 ... 180 °C 6.2301 7.3033 230.0

1) Used for frostpoint calculation if the dewpoint is negative

Mixing ratio:

99.621 

(2)

1 2 ... 160 161 162 163 164 165 166 167 168 169

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Vaisala DRYCAP DMT340 SERIES Betriebsanweisung Seite 165