DCS is a system of sensors, controllers, and associated computers that are distributed throughout a plant.
Each of these elements serves a unique purpose such as data acquisition, process control, as well as data storage and graphical display.
These individual elements communicate with a centralized computer through the plant’s local area network – often referred to as a control network. As the ‘central brain’ of the plant the DCS makes automated decisions based on production trends it sees them in real-time throughout a plant.
As an example the DCS at a power plant might automatically increase steam generation capacity of multiple turbines in order to keep up with changing demand for electricity during hot Summer days and then decrease it as outdoor temperatures cool overnight and demand subsides.
Whereas a PLC could adjust a single unit operation, the DCS can make adjustments to each of a plant’s many interacting unit operations.