1 PLC
(1) From the switch to control the development of sequence control, the delivery of treatment, is a bottom-up.
(2) Multi-purpose continuous PID control, PID stations in the interruption.
(3) Can be PC-based stations, more than for the same type of slave PLC.
(4) Can also be a PLC-based stations, more than the same type of PLC from the station, constitutes a PLC network. This is to make decisions with PC-Station is easy: when a user programming, communication protocols do not have to know, as long as written by the format specification will do.
(5) PLC as an independent grid can DCS / TDCS, can also be used as DCS / TDCS subsystem.
(6) Large-scale system with the DCS / TDCS, as TDC3000, CENTUMCS, WDPFI, MOD300.
(7) PLC network companies such as Siemens of SINEC-L1, SINEC-H1, S4, S5, S6, S7 and so on, GE’s GENET, Mitsubishi MELSEC-NET, MELSEC-NET/MINI.
(8) Mainly used for industrial process control in the order, the new PLC is also a combination of closed-loop control functions.
(9) Manufacturer: GOULD (United States), AB (U.S.), GE (U.S.), OMRON (Japan), MITSUBISHI (Japan), Siemens (Germany) and so on.



2 DCS or TDCS
(1) Distributed Control System DCS Distributed Control System and the TDCS is a 4C (Communication, Computer, Control, CRT) technology in the same monitoring technology.
(2) top-down system of the tree topology, in which communication (Communication) is the key.
(3) PID station in the interruption, the interruption of stations connected to the computer and on-site instrumentation and control devices.
(4) Is the tree topology and the link structure of a row of parallel, there are a large number of parallel cable from the relay station to the site instrumentation.
(5) Analog signals, A / D-D / A, mixed with the microprocessor.
(6) A line from a pair of instrument I / O, by the controller linked to a local area network LAN.
(7) DCS is the control (Engineers Point), operations (Operator Station), field instruments (field monitoring and control stations) of the three structures.
(8) The disadvantage is high cost, the company’s products are not interchangeable, and can not be interoperable, the DCS system is each different.
(9) For large-scale continuous process control, such as petrochemical, and other.
(10) Manufacturer: Bailey (U.S.), Westinghous (United States), HITACH (Japan), LEEDS & NORTHRMP (United States), SIEMENS (Germany), Foxboro (United States), ABB (Switzerland), Hartmann & Braun (Germany), Yokogawa (Japan), Honewell (United States), Taylor (U.S.) and so on.