Calibrating and adjusting HMT330 series and PTU300 series transmitters - HM70 - HMT330 - PTU300

HM70 User Guide

Document code
Document type
User guide

You can check and adjust the humidity and temperature channels of HMT330 and PTU300 with the HM70 meter. If you adjust both channels, make the temperature adjustment first. Calibrate your transmitter against a calibrated HMP70 series reference probe or against a calibrator's reference humidity by using the MI70 indicator in communication.

To connect HM70 to HMT330/PTU300 transmitters, you need the optional calibration cable (Vaisala item code 211339).

First carry out steps 1 ... 9. After 9, choose 1 of the alternative methods for completing the adjustment.

To start the adjustment:

  1. Connect calibration cable 211339 to the SERVICE PORT connector on the HMT330/PTU300 component board.
  2. Connect the other end of the cable to either one of the connector ports located on the bottom of the MI70 indicator. See Figure 1.
  3. Switch on both devices.
  4. The reading of the transmitter is shown on the first or middle row of the display, depending on the connector port to which the calibration cable is connected. The value of port I is shown on the upper row of the display and the value of port II on the lower row of the display. The difference of the readings is shown on the lowest row.
  5. If you are using an HMT330 unit with the optional chemical purge function, activate the chemical purge before calibration and adjustment. To activate the purge with the MI70 indicator:
    This step applies only to HMT330 series transmitters.
    1. Open Menu by pressing Open
    2. Select Functions and press Start and Yes
  6. Press the ADJ button on the component board of the HMT330/PTU300 transmitter to open the adjustment mode. The indicator LED on the component board starts to flash.
    After this step, the adjustment is carried out using the MI70 indicator.
  7. Press OK to start the adjustment.
  8. Select RH or T and press Select.
  9. If you selected RH, check the environment settings if necessary. If checking the environment settings is not necessary, press No.