SCADA (Supervisory Control and Data Acquisition) is a system that collects data from various sensors at a factory, plant, or in other remote locations and sends this data to a central computer that then manages and controls the data.
SCADA is a term that is used broadly to portray control and management solutions in a wide range of industries. Some of the industries where SCADA is used are Water Management Systems, Electric Power, Traffic Signals, Mass Transit Systems, Environmental Control Systems, and Manufacturing Systems.
SCADA as a System
There are many parts in a working SCADA system. A SCADA system usually includes signal hardware (input and output), controllers, networks, user interface (HMI), communications equipment, and software. All together, the term SCADA refers to the entire central system. The central system usually monitors data from various sensors that are either in close proximity or off site (sometimes miles away).
For the most part, the brains of a SCADA system are the Remote Terminal Units (RTU). The Remote Terminal Units consists of a programmable logic converter. The RTU are usually set to specific requirements. However, most RTU allow human intervention. For instance, in a factory setting, the RTU might control a conveyor belt’s setting and humans can change or override the speed at any time. In addition, any changes or errors are usually automatically logged and/or displayed. Most often, a SCADA system monitors and makes slight changes to function optimally. SCADA systems are considered closed loop systems and run with relatively little human intervention.
One of SCADA’s key processes is its ability to monitor an entire system in real time. Data acquisitions including meter reading, checking sensor statuses, etc. that are communicated at regular intervals depending on the system facilitate this. Besides the data that the RTU uses, data is also displayed to a human that interfaces with the system to override settings or make changes when necessary.
SCADA can be seen as a system with many data elements called points. Usually, each point is a monitor or sensor and can be hard or soft. A hard data point can be an actual monitor, while a soft point can be seen as an application or software calculation. Data elements from hard and soft points are always recorded and logged to create a time stamp or history
User Interface (HMI)
A SCADA system includes a user interface called a Human Machine Interface (HMI). The HMI of a SCADA system is where data is processed and presented to be viewed and monitored by a human operator. This interface usually includes controls where the individual can interface with the SCADA system.
HMIs are an easy way to standardize the facilitation of monitoring multiple RTUs or PLCs (programmable logic controllers). RTUs or PLCs run a pre programmed process, but monitoring each of them individually can be difficult because they are spread out over the system. Because RTUs and PLCs historically had no standardized method to display or present data to an operator, the SCADA system communicates with PLCs throughout the system network and processes information that the HMI easily disseminates.
HMIs can also be linked to a database, which can use data gathered from PLCs or RTUs to provide graphs on trends, logistic info, schematics for a specific sensor or machine, or even make troubleshooting guides accessible. In the last decade, practically all SCADA systems include an integrated HMI and PLC device, making it extremely easy to run and monitor a SCADA system.
SCADA Software and Hardware Components
SCADA systems are an extremely advantageous way to run and monitor processes. They are great for small applications such as climate control or can be effectively used in large applications such as monitoring and controlling a nuclear power plant or mass transit system.
SCADA can come in open and non-proprietary protocols. Smaller systems are extremely affordable and can either be purchased as a complete system or can be mixed and matched with specific components. Large systems can also be created with off the shelf components. SCADA system software can also be easily configured for almost any application, removing the need for custom made or intensive software development.