Vaisala HMP228 User Manual
Page 33
HMP228
M210282en-A
Operating Manual
27
4.4.5
Humidity calibration table
Temperature
°C
15
20
25
30
35
°F
59
68
77
86
95
LiCl
%RH
*
11.3
11.3
11.3
11.3
4...20 mA
5.81
5.81
5.81
5.81
0...20 mA
2.26
2.26
2.26
2.26
0...1 V
0.113
0.113
0.113
0.113
0...5 V
0.565
0.565
0.565
0.565
0...10 V
1.13
1.13
1.13
1.13
NaCl
%RH
75.6
75.5
75.3
75.1
74.9
4...20 mA
16.10
16.08
16.05
16.02
15.98
0...20 mA
15.12
15.10
15.06
15.02
14.98
0...1 V
0.756
0.755
0.753
0.751
0.749
0...5 V
3.780
3.775
3.765
3.755
3.745
0...10 V
7.56
7.55
7.53
7.51
7.49
Table 1
Greenspan's calibration table
*) If the LiCl solution is used or stored in temperatures below +18 °C (+64 °F), the
equilibrium humidity of the salt solution changes permanently.
4.6
Temperature calibration
The temperature channel has been calibrated at the factory and since it is very
stable, adjustment should be made only when there is strong reason to believe
that the adjustments have changed.
Temperature calibration should be performed against some accurate
temperature reference. It can be done either using the press switches inside the
housing, through the serial bus or the menus on the local display. Either a one
point offset correction or a two point calibration is possible.
Disconnect the security lock jumper!
4.6.1
One point offset correction
4.6.1.1
Using serial commands
•
Leave the reference instrument and the transmitter for at least 4 hours
in the same space so that their temperatures have time to equalize.
Remove the filter cap prior to calibration.
•
Check the transmitter against the reference.
•
Give command CT
>CT
T : 0.90 Ref1 ? yy.y
Press any key when ready
•
If you want to see how the sensor stabilizes to the reference
temperature, enter c