I. Overview Germany's Siemens (SIEMENS) produced PLC application in China are very wide, in metallurgy, chemical industry, printing production line applications in such areas. Siemens (SIEMENS) the company's PLC products include LOGO, S7-200, S7-300, S7-400, Industrial Networks, HMI human-machine interface, industrial software. Siemens S7 series PLC Small, fast, standardized, and has network communication capability, more powerful, more reliable. S7 Series PLC products can be divided into micro-PLC (such as the S7-200), small-scale performance requirements of the PLC (such as the S7-300) and in the high performance requirements of the PLC (such as the S7-400) and so on. 1. SIMATIC S7-200 PLC S7-200 PLC is the ultra-miniaturization PLC, it applies to all industries, all kinds of occasions, the automatic detection, monitoring and control. S7-200 PLC's power to run both stand-alone, or even into a network able to implement complex control functions