pid control with S7, FM355

  • Thread starter gino_mettepenningen
  • Start date

Thread Starter


The process have a heating and cooling circuit. Chiller is in use when airflow higher is than
21°C, heater is than closed.

Heater is in use when airflow lower is than 21°C, chiller is closed. I use a actuator with position feedback and limit stop signals, the controller is a step controller.

How can i control two actuators, for cooling and heating circuit? What can i do to prevent the actuators working against each other? Whats the best solution, working with one or two controllers in a control loop?
Use just one controller, split the range of the controllers output. For instance if the output is 4-20 mA then from 4-12mA will be used for cooling and from 12-20mA will be used for heating. The valves can be calibrated to work on the split range.
good luck