PID instruction in Allen Bradley PLC [Proportional/Integral/Derivative] Closed Loop Control For Processor SLC 5/02SLC 5/03SLC 5/04SLC 5/05 MicroLogix 1200 and MicroLogix 1500 (A special PID file replaces the old integer file control block.) Description of PID in PLC This output instruction is used to control physical properties such as temperature, pressure, liquid level, or flow rate of process loops. The PID instruction normally controls a closed loop using inputs from an analog input module and providing an output to an analog output module as a response to effectively hold a process variable at a desired set point. The PID equation controls the process by sending an output signal to the actuator. The greater the error between the setpoint and the process variable input, the greater the output signal, and vice versa. An additional value (feed forward or bias) can be added to the control output as an offset. The result of the PID calculation (control vari...


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