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Supervisory control and data acquisition (SCADA) is a
The SCADA concept was developed as a universal means of remote access to a variety of local control modules, which could be from different manufacturers allowing access through standard automation
The key attribute of a SCADA system is its ability to perform a supervisory operation over a variety of other proprietary devices.
The accompanying diagram is a general model which shows functional manufacturing levels using computerised control.
Referring to the diagram,
Level 2 contains the SCADA software and computing platform. The SCADA software exists only at this supervisory level as control actions are performed automatically by RTUs or PLCs. SCADA control functions are usually restricted to basic overriding or supervisory level intervention. For example, a PLC may control the flow of cooling water through part of an industrial process to a set point level, but the SCADA system software will allow operators to change the set points for the flow. The SCADA also enables alarm conditions, such as loss of flow or high temperature, to be displayed and recorded. A
Levels 3 and 4 are not strictly process control in the traditional sense, but are where production control and scheduling takes place.
SCADA systems typically use a tag database, which contains data elements called tags or points, which relate to specific instrumentation or actuators within the process system according to such as the