Instruction Manual

HMP230 SERIES
Appendix 6: Calculation formulas M210225en-B
134
The vapour pressure (in Pascals) is calculated using equation:
å
−=
Θ+Θ=
3
1
4
lnln
i
i
iws
bbP
(6)
where:
b
i
= coefficients
b
-1
= -0.58002206 * 10
4
b
0
= 0.13914993 * 10
1
b
1
= -0.48640239 * 10
-1
b
2
= 0.41764768 * 10
-4
b
3
= -0.14452093 * 10
-7
b
4
= 6.5459673
The parameters
A, m, and T
n
depend on temperature according to the follow-
ing table:
tAmT
n
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
When T
d
< 0 and the transmitter is set to dewpoint calculation mode (FROST
OFF), the parameters are as follows:
A = 6.119866 m = 7.926104 T
n
= 250.4138
When T
d
< 0 and the transmitter is set to frostpoint calculation mode (FROST
ON), the parameters are as follows:
A = 6.1134 m = 9.7911 T
n
= 273.47