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How SCADA Systems Work

SCADA System with Main Components

Four SCADA Functions

A SCADA system performs four main functions:

Data Acquisition

The collection of data frequently involves some kind of analog to digital conversion. Temperature is converted to degrees Celsius. Transmit signal strength is converted to dBm. Channel quality is measured in errored seconds.
1

Networked Data Communication

The collected data is transmitted either spontaneously or in response to a request for data to some kind of upstream consolidator or master. The communication channel can be analog (T202, POTS) or digital (RS485, TCP/IP). Contemporary channels typically include some kind of transport validation independent of any content validation.
2

Data Presentation

The collected data is processed, organized and presented for system operators to make appropriate response and control decisions. The presentation can vary from tabular presentation of logged events to graphical presentation against mapping or image backgrounds.
3

Control

If control decisions are warranted and the system supports output, appropriate commands can be dispatched to affect specific operational or configuration changes.
4

Four Main SCADA Components

A SCADA system performs four main functions:

Inputs

Inputs (either digital or analog) and output relays or electrical signals that directly interface with managed elements.
1

Remote Telemetry Units (RTUs)

These are small computerized units deployed in the field at specific sites and locations. RTUs (Remote Telemetry Units) serve as local collection points for gathering reports from sensors and delivering commands to control relays.
2

Data Presentation

The collected data is processed, organized and presented for system operators to make appropriate response and control decisions. The presentation can vary from tabular presentation of logged events to graphical presentation against mapping or image backgrounds.
3

Control

If control decisions are warranted and the system supports output, appropriate commands can be dispatched to affect specific operational or configuration changes.
4

Next Page: RTUs: Capacity, Function, and Installation.


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