When carrying out adjustments with the Modbus protocol, note that certain Modbus-specific adjustment requirements apply to HMP Series probes and HMP110 probes. Review the requirements before carrying out adjustments.
Modbus adjustment requirements
- RH can be calibrated and adjusted in 1–5 points, and temperature in 1–2 points. Note that you must write an empty (NaN) value in all fields for any unused adjustment points. This prevents any possible earlier values left in those points from affecting the adjustment you are carrying out.
- Adjustment points must be populated starting from point #1 (no empty points are allowed in between).
- All RH adjustment points must contain three values: reference value (after), measured RH (before), and measured T.
| NOTICE
At the end of the sensor life cycle, the sensor can no longer be adjusted to the specified accuracy and must be replaced. For more information, see return code -5 in Adjustment function return codes. The probe will reject adjustments that are too large (for example, for HMP Series probes adjustments greater than 10 %RH for humidity and 0.5 °C for temperature). If the probe appears to need such a large correction, perform a sensor purge (if available on the probe) and repeat the adjustment procedure. Make sure the measurement has stabilized and the reference environment is reliable. If the required adjustment is still too large, the probe needs to be serviced by Vaisala. |
Adjustment recommendations
For further information and instructions on probe adjustment, including general adjustment recommendations and requirements such as recommended reference humidity levels, see HMP Series User Guide M212022EN and HMP110 User Guide M211060EN. The probe documentation also describes the wiring, communication settings, and Modbus implementation of the probes.