Knowledge Base: Basic SCADA Component and How to Use Them

What SCADA is - and How to Make It Work for You

Supervisory Control And Data Acquisition: What is SCADA?

SCADA stands for Supervisory Control And Data Acquisition and is used to refer to distributed measurement and control systems that are larger in scale.

SCADA systems perform data collection and control at the supervisory level. This means that these systems can monitor, or "supervise" various network functions. They can also control elements based on pre-defined actions when certain conditions are present. Despite this, some SCADA systems only monitor without performing controlling functions.

A New Era: SCADA System History.

SCADA systems became popular in the 1960's as the need to monitor and control remote gear grew. Early systems were built from main frame computers and required human oversight to operate. This made early system expensive to use and maintain. Today, with new technology, SCADA systems are much more automated. They can serve efficiently. This reduces cost and overhead to companies with network alarming needs.

The Two Basic Elements of SCADA and How They are Used.

There are 2 basic elements of a SCADA system. First are the things you want to monitor. The second are devices you will use to perform monitoring and controlling functions. One of the main components of a SCADA system is having something you want to control. This could be a system or process, or even specific machinery. These SCADA-monitored elements could be just about anything. They could be an oil refinery plant. They could be a power-generation system. They could be an organization's communication network. They could even be a simple switch. The combination is endless.

The SCADA systems collect information from the system using a variety of sensors and control relays. Sensors are most likely referred to in 2 categories: Discrete and Analog. A discrete sensor is simply a type of sensor that returns either an on or off, yes/no type of response. It would be used to monitor things like the condition of a power feed: is it on or off? Or, is the door open or closed? Or, did someone just enter the building? These kind of On/off, Yes/no sensors are discretes. Analog sensors measure and report conditions that occur over a range of potential responses. Things like temperature, voltage, amperage, and water pressure all use analog sensors.

All of this information is collected and reported by Remote Telemetry Units, or RTU's where the sensors are located. These RTUs report back to master stations at a central location and are captured in many cases by a master station. This master station collects the data and puts it into a format that an operator can read and know. This completes the telemetry monitoring process.

SCADA System Components and Operation.

Every SCADA system is made up of four common elements. The first part of every system are the sensors and control relays. These can be either analog or discrete. These are the devices that monitor and control the managed processes and gear. This information is collected by the second part of every system, the RTUs.

These are devices deployed in the field at specific sites and locations. RTU's gather information locally from the sensors to report back to the SCADA master unit. RTU's can also issue control commands to the control relays it communicates with. SCADA master units, the third object in the system, are the main, user-end component of the entire monitoring system. They are also sometimes referred to as the SCADA HMI.

The master provides the central processing capability for the SCADA system. Master units connect the human staff to the system with a browser interface. This single view allows the system operator to respond to data gathered from all parts of the network. Finally, all of this data is sent from the remote locations to the master.

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Four Main Tasks Performed by SCADA Systems

All of these elements work together to perform four types of tasks. These are: data Collection, communication of data across the network, information reporting, and System control functions.

Data Collection involves what the name implies, that is collecting and assimilating data from various sensors. As we discussed before, discrete sensors collect information about simple events. Analog sensors can provide more detailed information that can fall within a range of values. Discretes are useful only for "present/not present" situations. Analog sensors are very useful in tracking environmental factors. These include temperature and humidity, battery levels, fuel levels, and more.

A communications network provides the needed channels to report this collected information back to a centralized location. Generally, this data is reported back from remote locations via Ethernet and IP. It is mostly sent using Synchronous Optical NETwork protocol (SONET) via fiber optic connections. To resolve security concerns when sending sensitive data, data should be sent over internal LAN/WANs, not the public Internet.

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