Adjustment Using Trimmers - HMM100

HMM100 Quick Guide

Document code
M211002EN
Revision
E
Language
English (United States)
Product
HMM100
Document type
User guide

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.

The trimmers will only turn 135 degrees each way, less than half a rotation. Do not force the trimmer past the stopping point.
Figure 1. Trimmers for Offset and Gain

The procedure below provides an example adjustment of offset and gain using the saturated salt calibrator HMK15. It is assumed that the module is powered and you can measure the output reading.

  1. Note the current position of the trimmers.
  2. Insert the probe in the LiCl salt chamber of the humidity calibrator (11 %RH), and wait for 20 – 40 minutes for the reading to stabilize.
  3. If necessary, adjust the offset trimmer using a small Phillips-head screwdriver to achieve the output reading that corresponds to 11 %RH.
    • For 4 ... 20 mA output, the reading should be 5.76 mA
    • For 0 ... 5 V output, the reading should be 0.55 V
  4. Insert the probe in the NaCl salt chamber (75 %RH) and wait for the reading to stabilize.
  5. If necessary, adjust the gain trimmer to achieve the output reading that corresponds to 75 %RH.
    • For 4 ... 20 mA output, the reading should be 16 mA
    • For 0 ... 5 V output, the reading should be 3.75 V
  6. Optional: repeat step 2 - step 4 to check the adjustment result. If you want to undo the adjustment, return the trimmers to their original position.