Detailed program as below:

(1).Temperature transmitter measures the inlet water temperature and send to temperature controller. The temperature controller calculates and transfers the temperature signal to the PLC.

(2). As the MPU, the PLC converts the needed air flow and pressure according to temperature signal.PLC controls the frequency converter and adjusts the fan speed to change the air flow and pressure.                                          http://www.chinacoolingfans.com/