SCADA
What is SCADA
SCADA (Supervisory Control And Data Acquisition) system refers to the combination of telemetry and data acquisition. It consists of collecting information, transferring it back to a central site, carrying out necessary analysis and control, and then displaying this data on a number of operator screens.The SCADA system is used to monitor and control a plant or equipment. Control may be automatic or can be initiated by operator commands.
What is telemetry
Telemetry is usually associated with SCADA systems. It is a technique used in transmitting and receiving information or data over a medium. The information can be measurements, such as voltage, speed or flow. These data are transmitted to another location through a medium such as cable, telephone or radio. Information may come from multiple locations. A way of addressing these different sites is incorporated in the system.
What is data acquisition
Data acquisition refers to the method used to access and control information or data from the equipment being controlled and monitored. The data accessed are then forwarded onto a telemetry system ready for transfer to the different sites. They can be analog and digital information gathered by sensors, such as flowmeter, ammeter, etc. It can also be data to control equipment such as actuators, relays, valves, motors, etc.
What are the differences between SCADA and DCS
Similar to the SCADA systems are the Distributed Control Systems (DCS). The DCS is usually used in factories and located within a more confined area. It uses a high-speed communications medium, such as local area network (LAN). A significant amount of closed loop control is present on the systemThe SCADA system covers larger.geographical areas. It may rely on a variety of communication links such as radio and telephone. Closed loop control is not a high priority in this system.
Components of SCADA System
Components of a SCADA System A SCADA system are composed of the following:
- Field Instrumentation
- Remote Stations
- Communications Network
- Central Monitoring Station
Field Instrumentation refers to the sensors and actuators that are directly interfaced to the plant or equipment. They generate the analog and digital signals that will be monitored by the Remote Station. Signals are also conditioned to make sure they are compatible with the inputs/outputs of the RTU or PLC at the Remote Station. The Remote Station is installed at the remote plant or equipment being monitored and controlled by the central host computer. This can be a Remote Terminal Unit (RTU) or a Programmable Logic Controller (PLC). The Communications Network is the medium for transferring information from one location to another. This can be via telephone line, radio or cable.
The Central Monitoring Station (CMS) refers to the location of the master or host computer. Several workstation may be configured on the CMS, if necessary. It uses a Man Machine Interface (MMI) program to monitor various types data needed for the operation. The following is a sample configuration of a SCADA system for water distribution.
The Central Monitoring Station (CMS) refers to the location of the master or host computer. Several workstation may be configured on the CMS, if necessary. It uses a Man Machine Interface (MMI) program to monitor various types data needed for the operation. The following is a sample configuration of a SCADA system for water distribution.
