目前，隨著微電子技術的發展，PLC控制系統的應用已經遠遠突破了早期的邏輯控制，從硬件到軟件、從單機到系統、從邏輯控制到過程控制，功能異常強大，產品非常豐富，以西門子、羅克維爾、施耐德等幾個知名品牌來說，產品系列非常齊全，幾乎每個系列又都覆蓋大、中、小各種規模的應用場合，給使用者全面、快速地掌握PLC的應用增加了很大難度。為闡述方便，本文從西門子S7系列PLC著手，希望從系統思維的角度來全面分析PLC控制系統在各種應用場合中產品選型與解決方案。
[Abstract] Now, with the development of micro-electronics, the application of PLC control system has breached the early logical control out and away. From hardware to software, from stand-alone to system, from logical control to process control , the functions are very strong, the product are very rich .Such as Siemens, Rockwell and Schneider , the product series are very complete , and the each series products almost cover with large , middle and small scale applications . This increases very difficulty for the custom to mastery PLC control technology entirely and rapidly . IN order to expatiate for its convenience , this article will do my best to entirely analyse the PLC selecting type and resolving projects from the angle of system thinking , according to the Siemens s7 series products.