Calibration - HMM100

HMM100 User Guide

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User guide

The recommended calibration interval is one year. You should also perform a calibration if the HMM100 does not appear to be within the specified accuracy.

The HMM100 can be adjusted in two ways:

  • Using the onboard trimmers. This method requires no serial connection, only a small Phillips head screwdriver and a suitable humidity reference. The trimmers can adjust up to ± 5 % of reading.
  • Using serial commands. This method requires a connection to the service port of the HMM100 module. For this, you need the USB cable (Vaisala order code 226068) and a PC with a terminal application. You also need a humidity reference and a Phillips head screwdriver for zeroing the trimmers.

As a humidity reference, you can use, for example, the Vaisala Humidity Calibrator HMK15. For more information on the HMK15, see Vaisala Humidity Calibrator HMK15 User's Guide.

Installing the probe properly will also help with the calibration. Ideally the probe should be placed completely in the environment, with enough cable to prevent heat conduction, and to allow the probe to be moved during calibration (placed in the HMK15 calibrator, for example).

If you have changed the HUMICAP sensor, center the trimmers, and perform a calibration and adjustment using the serial command CRH.
You can only calibrate the humidity measurement (RH) and temperature measurement (T). The module calculates the dewpoint using RH and T values.