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The most commonly used control systems in building automation are dcs control systems and plc control systems. What are the advantages of these two control systems?

1. Application

The initial design goal of PLC was to replace the complicated relay circuit. dcs was only used for industrial automation instrumentation at first; PLC emphasized the universality, dcs emphasized the specificity; PLC applied in the industrial control field, dcs applied in the specialized building system.

2. Structural differences

Dcs is a "decentralized control system". The composed system is a layered structure that can realize point-to-point communication. PLC is only a type of control "device" and is often used to control a certain part of a production line. The system consists of Special field bus connection protocol, PLC through the host computer and other PLC communications; both are "system" and "device" difference.

3. Agreement differences

The dcs system generally supports multiple protocol standards, has a rich integrated interface, and has a strong ability to integrate third-party devices. The system itself has better scalability and openness. And PLCs are basically all for individual work, and they are with other PLCs. When the upper computer communicates, the adopted network forms are basically single-network structures. The network protocol is generally a proprietary field bus standard, and the integration capability with third-party devices is relatively poor.

4. Software features

The host computer software of dcs system is mostly dedicated software; the host computer software of PLC system is mostly general configuration software. Specific to the field of building automation, the use of dedicated dcs is more convenient, especially the work of the host computer is relatively small; the use of PLC, whether it is the lower computer programming or host computer configuration are more troublesome, need to start from the foundation, the design of programming personnel The technical level and English requirements of the users are high.

5. Professionalism

PLC (such as commonly used Siemens S7200 and S7300) is a universal industrial control product. It does not have built-in rigorously tested energy management and energy-saving programs; it requires very professional designers to do a large number of on-site commissioning work, and the debugging cycle is long. Dcs curing professional software, there are standard applications and rigorous experimental PID algorithm and energy management program and other special features, dcs usually have: peak load control, optimization start and stop control, optimize equipment scheduling, energy cycle control, a variety of Air conditioning operation mode, temporary plan replacement, holiday schedule, basic calendar schedule, event schedule, trend record and report.