Humidity Controller

The Humidity Controllers regulate the temperature and relative humidity in BerILL chambers. Each system is connected to two thermostatic baths and operated by a Process Logic Controller M251 from Schneider. From the temperature and humidity setpoints provided by the user, the PLC determines the reservoir and sample temperatures (Antoine's equation). It then controls their variation using an overshoot technique (to earn time) or not. The touch screen graphical user interface displays the evolution of the physical parameters, the actual operated humidity chamber and other parameters.

As startup, the controller is in manual mode and the user must enter the sample and reservoir temperature setpoints. It is also possible to switch On/Off the heater of the goniometer and to request a goniometer temperature. In automatic mode, the user provides the temperature and relative humidity setpoints of the sample. The PLC calculates the temperature of the reservoir for the selected water (H2O or D2O). It enables automatically the heater of the goniometer whenever needed.

The PLC also provides an overshoot technique to speed up temperature and humidity changes: when enabled, the overshoot option requests the relative humidity setpoint + 10%RH until some condition is satisfied. This techniques relies on measurements performed in automatic mode at 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100%RH. The PLC stores automatically optimum parameters for each plateau and reuses them for altering the overshoot option.