Vaisala HMM100 - Manual (Page 56)

User's Guide _______________________________________________________________________
54 ___________________________________________________________________ M211024EN-C
Calibration and Adjustment Using Trimmers
HMM100 series modules have two trimmers mounted on the component
board. These trimmers allow for easy adjustment of the offset and gain of
the humidity measurement.
The modules are shipped with the trimmers centered. Turning the
trimmer counter-clockwise will decrease the offset or gain, and turning
clockwise will increase it. The adjustment range is ± 5% for both offset
and gain.
Offset correction requires a < 50 %RH reference. Offset and gain
correction requires additionally a > 50 %RH reference, with over 30
%RH difference between the two points.
NOTE The trimmers will only turn 135 degrees each way, less than half a
rotation. Do not force the trimmer past the stopping point.
0905-045
Figure 17 Trimmers for Offset and Gain
The procedure on page 55 provides an example adjustment of offset and
gain using the Vaisala Humidity Calibrator HMK15, which is a saturated
salt calibrator. It is assumed that the module is powered and you can
measure the analog output reading.
NOTE For best results, use the ACAL command to calibrate the currently active
analog output mode before using the trimmers. For instructions on how
to do this, see section Calibrate Analog Output on page 39.