Let’s discuss the differences between DCS and PLC

I’ll speak first. It seems that DCS includes PLCs, and a PLC is just a PLC, right?

Under current technical conditions, the difference between the two is not significant.

This post was last edited by RSchufaqi on 2017-6-13 at 11:27. PLCs and DCS have been discussed many times; here is a link for reference: http://bbs.hcbbs.com/forum.php?mod=viewthread&tid=1127841 http://bbs.hcbbs.com/thread-504369-1-1.html

It can be distinguished by definition~~~

It can basically be distinguished by definition~~~

A PLC is originally just a programmable logic controller; although today its functions have been expanded to include good performance in process control as well, it remains essentially just a controller. DCS is a control system whose components include management computer stations, operator stations, engineer stations, recording stations, field control stations, data acquisition stations, controllers, and more. It can therefore be seen that PLCs can serve as part of a DCS system (as controllers or for data acquisition); of course, the field control stations or data acquisition stations of a DCS can also use other devices such as PACs, RTUs, and remote I/O units. Even when multiple PLCs are used to carry out a certain task, it is merely because there are a large number of I/O points that need to be monitored and controlled; in other words, the field control station or data station becomes larger. Thus, the relationship between DCS and PLC is one of inclusion and being included. Of course, for simple applications, a PLC can operate independently to carry out certain tasks. The configuration of DCS is highly flexible; it can be composed of dedicated management computer stations, operator stations, engineer stations, recording stations, field control stations, and data acquisition stations, or it can be built using standard servers, industrial control computers, and programmable controllers. The process control level at the lowest tier typically carries out data acquisition and control locally through dispersed field control stations, data acquisition stations, etc., and transmits the data to the production monitoring level computers via a data communication network. The production monitoring level performs centralized operation and management of data from the process control level, such as various optimization calculations, statistical reports, fault diagnosis, and alarm display.

DCS is my own wife; I can view it and operate it； PLC is someone else’s wife; it can only be viewed, not operated

PLC is open, a bit like Android, while DCS is closed, a bit like Apple. PLCs excel at logical operations, while DCSs are strong in analog operations.

I won’t go into explanations of PLCs and DCSs; there’s not much to say – one is a specific controller, while the other is an entire control system. In simple terms, today’s PLCs and DCSs differ little in terms of functionality; both can be used for displaying and controlling industrial process variables. Moreover, it is now very easy to equip PLCs with a host computer. PLCs are commonly used in small control systems; they are inexpensive and self-contained, allowing them to handle the control tasks of an entire device on their own. The control unit is housed in a single cabinet, and they are often used in projects with a limited number of control points or in complete sets of equipment ； DCS is commonly used for controlling large-scale factories; it is capable of managing complex control processes involving a large number of points. Its safety and stability, along with its scalability and standardization, give it significant advantages in the overall control of multiple devices. Its structure consists of at least one or more cabinets, along with a set of upper-level computer systems (such as operator stations and engineer stations – in short, computers in general). It’s not a large project, so it’s not worth using DCS. Furthermore, PLCs have significant disadvantages in terms of lightning protection, as it is impossible to avoid induced currents; therefore, it is inevitable for PLCs to be damaged in stormy areas……