How much time does PID control take for one control cycle?
Thread Content
Hello everyone! How long does it take for a PID control system to complete one full control cycle? That is, from the measurement value taken by the field transmitter to the DCS, then the measurement value is compared with the setpoint to generate an OP value that is sent to the field control valve; the control valve then acts, and the field transmitter measures the resulting change and sends this value back to the DCS. How long does this process take? (It’s not the time required for the entire system to reach stability, but merely the time needed for one control cycle.) How can this be calculated?
The valve on site is a pneumatic control valve
You can refer to the parameters for the control cycle in DCS
Reply 3# heartoking: DCS only knows the time related to DCS; it’s impossible for DCS to know the time required by control valves.
According to the manufacturer, it currently takes about 0.2 ms for a CPU to process one PID； Then, based on this set scanning period, if the scanning period is 1 second, the maximum number of tasks that can be processed by this station is 5000; if the scanning period is 200 milliseconds, then only 1000 tasks can be handled by this station ； This is only a theoretical value, as not everything at a single station can be regulated by PID; therefore, the actual number of points is somewhat higher than this.