PLC and PID Controller : In general terms PLCs are probably one of most widely used pieces of control and automation technology. The clue really comes from the name PLC, or “programmable logic controller”. It is the fact that they are programmable that makes them so versatile in their application. PLCs contain a processor, memory to hold their programming and other data and input and output modules.
PLC and PID Controller : PID control is used where greater levels of precision in control are required. It combines three control terms to give a single output to drive the setpoint. The Proportional band gives an output that is proportional to the error (the difference between the setpoint and the actual process value). The controller is tuned with a proportional band range that aims to get the process value to the setpoint in the shortest time without prolonged oscillations around the setpoint. If the band is set too wide, full power will be removed while there is still a large error and the setpoint will not be reached.