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Supervisory Control and Data Acquisition (SCADA) Overview

A SCADA (Supervisory Control and Data Acquisition) system is a computer application that is used to monitor and control a plant or equipment at the supervisory level. The term "SCADA", as it is normally used, refers to a centralized monitor and control system of a complete network, or sometimes to an individual site that covers a long distance.

A SCADA system can also be referred to as a SCADA Solution.


To have an efficient SCADA system, it's necessary to choose the perfect-fit monitoring device for your needs.

SCADA Systems Can Detect and Correct Network Problems

SCADA systems can be used to manage any type of equipment. Companies in the water and waste control, energy, oil and gas refining, transportation, and telecommunications industries commonly use these systems to automate complex industrial processes, detect and correct problems, and measure trends over time.

SCADA systems provide companies monitoring and control applications by collecting and analyzing real-time data. Though not all SCADA systems are equipped for controlling functions, they are still referred to as SCADA systems.

The four functions performed by a SCADA system are:

  1. Data acquisition

  2. Networked data communication

  3. Data presentation

  4. Control

What are The SCADA System Components?

The components of a SCADA system that perform the important system functions are sensors and control relays, Remote Telemetry Units (RTUs), SCADA master units, and the communication network.

Included in a SCADA system are input/output signal hardware, networks, a HMI (Human-Machine Interface), controllers, communication, a database, and software.

RTUs VS PLCs

Most of the site control performed by a SCADA system is actually performed automatically by two types of devices, either RTUs or PLCs (Programmable Logic Controllers).

Data such as equipment status and meter readings are collected at the RTU or PLC level. If a system is designed to support alarm collection, that will also be done at this level.

Many operators design their SCADA systems using PLCs to save money, but this ends up costing them in the long run. RTU devices feature much more advanced functionality, allowing for much more efficient and secure monitoring than a SCADA system comprised of PLCs.

Human-Machine Interface Communicates Status and Alarm Information

The HMI serves as the master station that communicates the processed status and alarm information collected along the SCADA system to the human operator.

The HMI combines these pieces of data from the system into one place, saving operators from manually combining polled data from individual points.

Operators can view the system alarms and information through the HMI, and they can make educated decisions based on these readings. If a system is equipped with control functions, signals can be sent back to the RTUs to execute certain actions.

The Best Transport for SCADA Information

The communications within these SCADA systems were initially designed to take place over radio or direct modem or serial connections. Today, it is more common to employ Ethernet or IP over SONET for SCADA system communications.

For security reasons, SCADA information should be kept on closed LAN or WAN networks that prevent sensitive data from being exposed to outsiders over the Internet. However, LAN can be very expensive to install at your remote sites!

NetGuardian 832A Allows for Cost-Effective LAN Migration Over Time

The NetGuardian 832A supports serial and dial-up in addition to LAN communication.

When a NetGuardian is located at a remote site outside your LAN, it can support the existing communications methods, preventing the need to install expensive LAN for all remote sites. However, as your company expands their LAN network over time, you can simply switch their NetGuardian RTU devices to the LAN port, saving thousands of dollars on RTU replacements to support the new network.

This allows for LAN migration over several budget cycles without having to replace RTUs throughout the network.


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There is no other network on the planet that is exactly like yours. For that reason, you need to build a monitoring system that's the right fit for you.

"Buying more than you need" and "buying less than you need" are real risks. You also have to think about training, tech support, and upgrade availability.

Send me a quick online message about what you're trying to accomplish. I'll work with you to build a custom PDF application diagram that's a perfect fit for your network.


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