A control system is decided the real-time control system if able to respond with appropriate input logically and quickly. Thus, the control system which has a response time fast enough so that they can respond the input within a limited period of time required, the control system can be referred to as a real-time control system. Any slow response of a system, if it is still able to meet response time constraints are required, it still says the system is real-time.
A temperature controller on an electric-heated Curing Vessel that used in the curing process (cooking) rubber compound does not require fast response-time. In this system, the rate of change of temperature is ± 1.5 degree Celsius per minute with the maximum attainable temperature of 160 degrees Celsius.
For this kind of system, the temperature controller with cycle-time of 10 seconds was enough. Controller does not need to take sampling temperature with excessive frequency because of its speed is only 1.5 degrees Celsius per minute.
And what about the PLC? For instant PLC OMRON CPM1A or CPM2A. Both have an I/O Response-Time and Cycle-Time, which is very fast. That’s why control systems base on PLC can be categorized as a system of real-time control.