Modules of a SCADA.
The modules or software blocks that allow the acquisition, supervision and control activities are the following:
Configuration: allows the user to define the working environment of his SCADA, adapting it to the particular application that he wishes to develop.
Operator graphic interface: provides the operator with control and supervision functions of the plant. The process is represented by graphic Synoptics stored in the process computer and generated from the editor incorporated in the SCADA or imported from another application during the configuration of the package.
Process module: executes the preprogrammed control actions based on the current values of variables read.
Management and data archiving: it is responsible for the storage and orderly processing of the data so that another application or device can access them.
Communications: is responsible for the transfer of information between the plant and the hardware architecture that SCADA supports, and between it and the rest of the IT management elements.
Hardware in supervision systems: PLC and PC
The fact is that the automated control, visualization and computing tasks can be carried out by PLCs (connected in a network using the appropriate modules) better than with exclusive PC-based control systems. What is ultimately practical, however, depends on a large number of factors and most must be considered individually for each automation project. Thus, for example, the current knowledge and preferences of the user can play a greater role than the pure power of the computer.
The crucial factors, not However, they are the real-time capacity attributes and the security properties that have been strongly associated with the PLC until now, although the PC can also have the capacity feature in real time.
A control system is inconceivable without real-time capability. It is common in computer control systems to have to choose, depending on the characteristics of the system to be monitored, between the PLC or the PC. You must choose the hardware that best suits the needs of the system to be monitored.
Programmable logic controllers, in most cases, are specifically designed to be used in demanding industrial environments and have been continuously developed so that their real-time operating systems represent their greatest virtue. They are and will continue to be, however, the first choice for all control of critical or extreme tasks due to their performance and simplicity, in which a PC could simply be “overloaded” due to the work that can be done by other tasks of common scope, as the management and visualization of data, access to peripherals, databases, etc …
If, in addition to task control, data processing, networking or visualization (a SCADA application) is required, a PC-based system must be taken into consideration.
In terms of operating systems, Windows NT, for example, is not strictly a real-time operating system like a PLC, but can act fast enough for “soft” applications in real time, thanks to its micro-architecture. kernel