SCADA

Under Supervisory Control and Data Acquisition ( SCADA) is defined as the monitoring and control of technical processes by means of a computer system.

Concept

Automated systems are divided according to the OSI model into several layers. This is illustrated by the automation pyramid.

Here, the level 1 is the process-oriented layer. The term SCADA usually refers to centralized / decentralized systems that monitor the entire installation, visualize and control and regulate. Most of the control is automatically remote control terminal (RTU ) or performed by programmable logic controllers ( PLC) or Level 1 automation.

The task of the Level - 2 automation is to optimize the function of the Level -1 - automation, and output control variables and setpoints. The Level 3 automation is, however, planning, quality assurance and documentation.

Data collection usually begins with the Level 1 and includes the coupling to instrumentation and status information such as switch positions, which are detected by the SCADA system. The data is then presented in a user-friendly display and allow controlling intervene in the process.

SCADA systems typically implement a distributed data base that contains data points. A data point contains an input or output value which is monitored and controlled by the system. Data points can be calculated physically. A physical data point represents an input or output, while a calculated point can be seen by mathematical operations from the state of the system. Normally, data points are treated as a combination of values ​​with time stamp. A series of data points allows the historical evaluation.

Communication

The communication within SCADA systems is now more and more based on TCP-based Internet technologies. At the field level but also play serial connections in the form of point-to- point communications and field bus systems, an important role that is likely to remain get the foreseeable future. The standardization of communication is not yet complete. Experiments such as OPC often limited even on certain operating systems, although here now a step towards operating system independence (OPC XML DA, OPC UA) is gone. Frequently used in SCADA vendor-specific or closed-form solutions are still to be found. But open protocols such as Modbus enjoying growing popularity. Gateways in the form of embedded systems, different transmission protocols can adapt to each other. The jobs, where is visualized, are now increasingly via Ethernet or wireless networks, ie more connected based on the TCP.