Emphasis is different: DCS focuses more on the process control field (such as chemical industry, smelting, pharmacy, etc.). ).), mainly to monitor and adjust some field parameters. PLC focuses on logic control (machining). Of course, now PLC can also deal with process control problems well, but it is not professional in DCS. Difference of analog quantity: DCS is generally used when the analog quantity is greater than 100, and PLC is generally used if the analog quantity is less than 100. Different network forms: DCS network is the central nerve of the whole system, and DCS system usually adopts the international standard protocol TCP/IP. It is a safe and reliable double redundant high-speed communication network, and the system has good expansibility and openness. Because PLC basically works for a single small system, when communicating with other PLCs or hosts, the network form adopted is basically a single network structure, and the network protocol is often inconsistent with international standards. Different faults occur: all I/O modules of DCS system are equipped with CPU, which can realize the quality judgment and scalar transformation of collected output signals, and the faults can be switched online and replaced randomly. The PLC module is just a simple electrical converter, and there is no intelligent chip. After the failure, all the corresponding units were paralyzed.