Vaisala HMP46 - Manual (Page 12)

HMI41 AND PROBES
Operating Manual
M210316EN-A
8
5. CALIBRATION
The HMI41 indicator and probes are fully calibrated at the factory, so there
should be no immediate need for recalibration. Calibration is recommended
once in a year and always when there is a reason to believe that the
adjustments have changed.
5.1 Calibration with trimmer potentiometers
5.1.1 Humidity calibration
Humidity calibration of the probes is preferably done by adjusting the trimmer
potentiometers. The potentiometers are located under a protective plug. The
potentiometer marked T (temperature) is for factory use only; DO NOT make
any adjustments. To make sure that this potentiometer is not accidentally
touched when adjusting the other two, turn the plastic plug aside without
removing it completely (see Figure 5.1.1).
For adjusting the potentiometers, use a trimming wrench provided with the
probe, or some other suitable tool, e.g. a ceramic 1.5 mm slot screwdriver.
T W D
W
D
dry
wet
HMP46
HMP41 &
HMP45
wet dry
W
D
Figure 5.1.1 Location of trimmer potentiometers
A two point calibration is performed with the HMK15 calibrator or the probe
can be sent to Vaisala. The probes must always be recalibrated when the
sensor is changed.