PID-Based Temperature and Level Control of a Process Tank Using a Siemens PLC Training Kit

Temperature and level are among the most common controlled variables in process industries. This paper describes a closed-loop PID control system for the temperature and level of a process tank designed for a Siemens PLC training kit and evaluated by simulation. Analog sensor signals are scaled to engineering units inside the PLC, and PID algorithms drive a heating element and a pump or valve. The controller is tuned from simulated step-response tests and assessed by rise time, overshoot, settling time and steady-state error. In simulation the temperature loop reached a 90 % rise time of 340 s with 0.0 % overshoot and a steady-state error of -0.002 °C, and the level loop settled in 64 s without steady-state error.