Vaisala HUMICAP HM44, User Manual, Page: 39 / 52

Chapter 8 ________________________________________________________________ Calibration
VAISALA __________________________________________________________________________ 37
Two-point humidity calibration
In two-point humidity calibration, two accurate references (e.g. the HMK15 Calibrator) are
needed. Leave the reference instrument and the probe at the calibration site for at least 1 hour
so that the probe temperature stabilizes to the room temperature. Start the calibration by
inserting the probe to the lower reference humidity. In setup mode press ENTER repeatedly
until the following is displayed:
set
Then press MODE three times, and the following appears:
RH
set
Press ENTER to activate the two-point humidity calibration mode. A message similar to the
following appears with the first line blinking:
RH
set
%
Lo
The blinking number indicates the value of the lower humidity reference stored in the HMI41
memory. Check the salt chamber temperature, read the closest humidity value in the
calibration table and adjust the display with buttons
▲
and
▼
to correspond to the value given
in the table. For example, if the temperature of the LiCl salt chamber is 22 °C, adjust the
value to 11.3 %RH:
RH
set
%
Lo
Press ENTER, and the HMI41 shows the value that the probe is currently measuring.
Wait for the reading to stabilize (about 30 minutes) and then press ENTER. Now the lower
humidity value is corrected to the given low reference. Press ENTER again to conclude the