| SCADA is an acronym that stands for | | | | consisting of a central host or master (usually |
| Supervisory Control and Data Acquisition. SCADA | | | | called a master station, master terminal unit or |
| refers to a system that collects data from | | | | MTU); one or more field data gathering and |
| various sensors at a factory, plant or in other | | | | control units or remotes (usually called remote |
| remote locations and then sends this data to a | | | | stations, remote terminal units, or RTU's); and a |
| central computer which then manages and | | | | collection of standard and/or custom software |
| controls the data | | | | used to monitor and control remotely located field |
| SCADA systems are used not only in industrial | | | | data elements. Contemporary SCADA systems |
| processes: e.g. steel making, power generation | | | | exhibit predominantly open-loop control |
| (conventional and nuclear) and distribution, | | | | characteristics and utilise predominantly long |
| chemistry, but also in some experimental facilities | | | | distance communications, although some elements |
| such as nuclear fusion. The size of such plants | | | | of closed-loop control and/or short distance |
| range from a few 1000 to several 10 thousands | | | | communications may also be present. |
| input/output (I/O) channels. However, SCADA | | | | Systems similar to SCADA systems are routinely |
| systems evolve rapidly and are now penetrating | | | | seen in factories, treatment plants etc. These are |
| the market of plants with a number of I/O | | | | often referred to as Distributed Control Systems |
| channels of several 100 K: we know of two cases | | | | (DCS). They have similar functions to SCADA |
| of near to 1 M I/O channels currently under | | | | systems, but the field data gathering or control |
| development. | | | | units are usually located within a more confined |
| There are many parts of a working SCADA | | | | area. Communications may be via a local area |
| system. A SCADA system usually includes signal | | | | network (LAN), and will normally be reliable and |
| hardware (input and output), controllers, networks, | | | | high speed. A DCS system usually employs |
| user interface (HMI), communications equipment | | | | significant amounts of closed loop control. |
| and software. All together, the term SCADA | | | | SCADA systems on the other hand generally |
| refers to the entire central system. The central | | | | cover larger geographic areas, and rely on a |
| system usually monitors data from various | | | | variety of communications systems that are |
| sensors that are either in close proximity or off | | | | normally less reliable than a LAN. Closed loop |
| site (sometimes miles away). | | | | control in this situation is less desirable. |
| An industrial measurement and control system | | | | |