A closed-loop control system for position control is comprised of proportional integral and derivative circuits and is often referred to as a PID (proportional–integral–derivative controller )

PID control is a common closed-loop system used to maintain physical property such as pressure and temperature in automated processes. the PID instruction controls the closed-loop by comparing the input or process variable from an analog input module to the system setpoint the difference between the setpoint and the process variable is referred to as the error.

The error is analyzed by the PID Loop calculation and provides an output or control variable to an analog output module to meet the setpoint defined by the system requirements.