The Design and Realization of PID Liquid Level Control System Based on S7-200 and EM235

摘要

With the development of microelectronics and computer technology, the PLC's (Programmable Logic Controller's) abilities of calculation and I/O interface become more and more powerful. After introducing the A/D and D/A in PLC system, it is currently able to solve more than the simple logic control. And the performance of analog quantity control through expanding modular is outstanding, particularly in system with small or middle scale. We take PLC of S7-200 series as foundation to design a set of analog quantity control system (mainly carry on the PID control on it). We will master capacity of analyzing the idiosyncrasy of closed loop control system. Realizing how to input/output analog quantity with the help of transmission instruction, principle of PID arithmetic, how to set control parameters, and complete PID by programming in Ladder Logic Diagram.