Adjusting humidity and temperature with push buttons - HMT120

HMT120 User Guide
Document code
M211244EN
Revision
D
Language
English
Product
HMT120
Document type
User guide
The instructions here apply to both 1-point and 2-point calibration.
To make a humidity or temperature adjustment:
  1. Open the transmitter cover. There are 3 buttons marked ADJ, + and - on the component board. There are also two indicator LEDs, one green and one red.
  2. Press the ADJ button and hold it down until the green indicator LED begins to blink slowly (800 ms cycle time).
  3. The transmitter is now in RH calibration state. Analog output and optional display will still follow the actual measured RH value.
    If you do not wish to perform the RH adjustment at this time, press the ADJ button one more time. The green indicator LED turns off and the red indicator LED begins to blink slowly (800 ms cycle time) to indicate T calibration state. To calibrate T, follow the instructions starting from step 7.
  4. Remove the filter and insert the probe into a measurement hole of the dry end reference chamber (for example, LiCl: 11 %RH) to do the low humidity offset adjustment.
    Do not touch the adjustment buttons before the conditions have stabilized. This takes approximately 30 minutes.
  5. Press either the - or + button at least once, make sure that the Iout current is correct, adjust using the - and + buttons if needed, and press the ADJ button again. The green indicator LED begins to blink faster (400 ms cycle time).
    If you do not wish to perform the two-point RH adjustment at this time, press the ADJ button one more time. The green indicator LED turns off and the red indicator LED begins to blink slowly (800 ms cycle time) to indicate T calibration state. To calibrate T, follow the instructions starting from step 7.

    If one-point calibration is done at more than 50 %RH, a gain adjustment is done instead of an offset adjustment.

  6. Insert the probe into the high end reference chamber (for example, NaCl: 75 %RH chamber in the humidity calibrator HMK15) and do the high humidity gain adjustment by using the - and + buttons to make sure the Iout current is correct (you have to press either - or + at least once even if the value is correct). To finish the RH calibration, press the ADJ button. The green LED is now turned off and the red indicator LED begins to blink slowly (800 ms cycle time).
  7. The transmitter is now in T calibration state. Analog output and optional display will still follow the actual measured T value.
    If you do not wish to perform the T adjustment at this time, press ADJ button one more time. The red indicator LED is turned off and the transmitter returns to normal mode. The calibration procedure is now finished.
  8. Insert the probe into a known reference temperature (if Vaisala Humidity Calibrator HMK15 is not used) and let the temperature reading stabilize.
    Do not touch the adjustment buttons before the conditions have stabilized.
  9. Using the - and + buttons, make the temperature offset adjustment by making sure the Iout current is correct (you have to press either - or + at least once even if the value is correct) and press the ADJ button. The red indicator LED begins to blink faster (400ms cycle time).
    If you do not wish to perform the two-point T adjustment at this time, press the ADJ button one more time. The red indicator LED is turned off and the transmitter returns to normal mode. The calibration procedure is now finished.
  10. Insert the probe into another reference temperature.
    Do not touch the adjustment buttons before the conditions have stabilized.
  11. Using the - and + buttons, make the temperature gain adjustment by making sure the Iout current is correct (you have to press either - or + at least once even if the value is correct).
  12. Press the ADJ button one more time. The red indicator LED turns off and the transmitter returns to normal mode. The calibration procedure is now finished.
In case of calibration error, both LEDs blink alternately at a very fast rate (cycle time 200ms) for a period of 2s after which the transmitter returns to normal mode.
If your transmitter has the optional display, the following notifications are shown on the display during calibration:
  • Probe cal: RH 1 (corresponding the green LED blinking slowly)
  • Probe cal: RH 2 (corresponding the green LED blinking fast)
  • Probe cal: T1 (corresponding the red LED blinking slowly)
  • Probe cal: T2 (corresponding the red LED blinking fast)
  • Probe cal: Error (corresponding both LEDs blinking alternately at very fast rate)