4 humidity calibration table, 2 temperature calibration – Vaisala HMP260 User Manual
Page 50
HMP260 SERIES
Operating Manual
HMP260-U017en-1.5
44
1997-11-25
•
Check that the reading corresponds within the desired accuracy to the
reading in the calibration table. If not, adjust the second point with the
arrow switches to the correct value and press ENT. At the second
calibration point the second LED from the left flashes.
The basic capacitance of the new sensor may differ considerably from that of
the previous one. Therefore the corresponding humidity reading of the
transmitter may be below 0 %RH at the low or above 100 %RH at the high
calibration point. However, the current/voltage reading of the analogue output
shows only the minimum or maximum value of the selected current/voltage
scale and the output value may not change even though the arrow switches are
pressed several times. If this happens, press the up or down arrow switch
continuously to bring the output back into the selected scale; this may take as
long as half a minute.
6.1.4
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
*)
LiCl solution must not be used or stored in temperature below +18 °C,
otherwise the equilibrium humidity of the salt solution changes permanently.
6.2
Temperature calibration
The temperature channel has been calibrated at the factory and since it is very
stable, calibration should be performed only when there is strong reason to
believe that the adjustments have changed.
Temperature calibration should be made 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 or a
two point calibration can be done.