What is SCADA?

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The term SCADA is short for: Supervisory Control and Data Acquisition.

SCADA is hardware and software that allows you to:

Who uses SCADA?

SCADA finds uses in a wide range of applications. For example:

  • Brewing
  • Chemical production
  • Desalination
  • Environment Control
  • Food production
  • Horticulture
  • Oil and Gas
  • Pharmaceuticals
  • Pipelines
  • Power generation
  • Production Lines
  • Solar arrays
  • Waste treatment
  • Wind farms
  • Wine production

Operators use SCADA to be informed about their application. Using a SCADA system, operators can:

A SCADA System Architecture

A simple SCADA system might use these components:

A simple SCADA system showing the SCADA software connected to PLCs.

In this example, each PLC connects to equipment and sensors. The SCADA software communicates with each PLC to:

This example shows a PLC as the interface between the SCADA system and the equipment. An RTU or a Remote I/O unit could also be used.

Operators use the information provided by the SCADA system to manage their Automated Process.

What type of Information Does SCADA Provide?

SCADA Systems provide these types of information:

Graphic Page:

A SCADA Graphic Page.

A Graphic Page is usually a diagram of the equipment with actual measurements shown live on the page. Color and text is used to indicate equipment state. For example:
  • Red is often used to indicate stopped or failed.
  • Green is often used to indicate running or normal.
A SCADA system will usually have more than one Graphic Page. A large SCADA system could have hundreds of pages. Using a Graphic Page, operators can:
  • Check the equipment for correct operation.
  • Click links to show other Graphic Pages, Trends, or Data List.
  • Issue commands or enter information.

A trend.

A Trend is a plot of one or more measurements over a time period.

Operators can use trends to check that measurements fit with expected patterns.

Alarm List:

An alarm list.

The Alarm List shows the abnormal conditions. For example:
  • A piece of equipment fails.
  • A measurement too high or too low.
Operators are notified of alarms and can take action to solve the issue.
Event Log:

An event log.

The Event Log is a timeline of important events on the system. For example:
  • A user logs on.
  • A batch process starts or completes.
  • Equipment changes to a new state.
  • A measurement moves outside its expected range.
  • An Operator issues a command.
If an incident occurs, Operators can use the Event Log to see the sequence of events up to the incident.

SCADA Software

Modern SCADA software is a set of programs and modules that provides the features of the SCADA system.

SCADA Server

The SCADA Server.

The SCADA Server is a service (or daemon) that runs in the background. The SCADA Server:
  • Runs Drivers to interface with each PLC or data source.
  • Manages the SCADA Database. The SCADA Database contains:
    • Tag configuration and data.
    • Graphic pages.
    • The list of alarms (abnormal conditions).
    • Historical data for Trends.
    • Event data for the Event Log.
  • Accepts connections from, and provides data to:
    • The operator interface.
    • Configuration tools.
    • Data Interfaces.
Operator Interface

The SCADA Operator Interface.

The Operator Interface connects to the SCADA Server to provide the information Operators need. For example:
  • Graphic Pages
  • Trends
  • Alarm List
  • Event Log
Multiple Operator Interfaces can connect to the same SCADA Server. This allows many Operators to jointly manage the same Automation Process.

SCADA Drivers.

A Driver is an interface between the SCADA Server and an external device. Different Drivers are created for each protocol or device family. Common Drivers found in SCADA Systems include:
  • Modbus
  • OPC Client
  • DNP3
  • SNMP
  • MQTT
  • Allen Bradley PLC
  • Mitsubishi PLC
  • Omron PLC
  • Siemens PLC
Data Interfaces

SCADA Data Interfaces.

Some SCADA Applications require an interface to other systems. For example MES or ERP.

A SCADA system should provide Data Access interfaces to make this possible.

Setting up a SCADA System

To provide useful information to Operators, a SCADA system will need to be configured.

An Engineer normally configures a SCADA system. To do this the Engineer will:

Terms Used in SCADA

The terms we have used in this article reflect the terms we use to describe Fernhill SCADA. Different SCADA vendors often use different terms to describe the same, or similar, feature. For example:

Fernhill SCADA TermCommon Alternative
Graphic Page Display, Screen, Window, Graphic, Mimic, Diagram
Trend Graph, Historical Trend, Plot
Alarm List Alarm Log
Event Log Event List

Learn About Fernhill SCADA


Fernhill SCADA has a simple licensing model:

Supported Platforms

Fernhill SCADA works on different platforms:

Further Information

Fernhill SCADA Concepts

To learn about other Fernhill SCADA Concepts.

Fernhill SCADA Operator Interface

To learn about the Operator Tools in Fernhill SCADA.

Fernhill SCADA Configuration Tool

To learn how to configure Fernhill SCADA.


For the meaning of terms used in Fernhill SCADA.