DCS is a system including upper-level software,network and controller,while PLC is just a controller.To form a system,an upper-level SCADA system and a network connected to it are also required.
For PID loop control,now Mitsubishi’s process controller can also implement FBD programming like SAMA configuration;the DCS system is larger,the number of control loops is more,and there are more controls and algorithms,which can complete more complex loops.control.Hardware reliability is about the same.DCS can achieve I/O redundancy,but PLC cannot.Relatively speaking,the system cost constituted by PLC is lower
DCS是一个系统包括上位软件、网络与控制器，而PLC只是一个控制器，要构成系统还需要上位SCADA系统和与之相连的网络。
对PID回路控制，现在三菱的过程控制器也可以实现象SAMA组态一样的FBD编程；DCS系统更大，控制的回路数目更多，有比较多的控制和算法，可以完成比较复杂的回路间的控制。硬件可靠性差不多。DCS可以做到I/O的冗余，PLC则不可以。相对而言，PLC构成的系统成本更低。
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