可编程的逻辑控制器(PLC)是专门为在工业环境下使用而设计的工业控制计算机,它具有如下一些优点:能在恶劣的环境下可靠工作,且具有修改程序容易的特点。体积小、结构紧凑,接线方便简单,易于机器构成一个整体。功能扩展方便,各大厂家都相继生产出了PID模块;A/D模块,高速计算器模块等功能模块供用户选用。因此,用PLC设计自动控制系统已成为世界潮流。近几 Programmable logic controllers (PLCs) are industrial control computers designed for use in industrial environments. They have the following advantages: Reliable operation in harsh environments with easy-to-modify programs. Small size, compact structure, easy wiring, easy to form a whole machine. Easy expansion of functions, all major manufacturers have produced a PID module; A / D module, high-speed calculator module and other functional modules for users to choose. Therefore, using PLC to design automatic control system has become the world trend. Recent