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A distributed control system (DCS)

[i]n a control system, refers to control achieved by intelligence that is distributed about the process to be controlled, rather than by a centrally located single unit.[1]


A DCS is used to control industrial processes such as electric power generation, oil refineries, water and wastewater treatment, and chemical, food, and automotive production. DCS are integrated as a control architecture containing a supervisory level of control overseeing multiple, integrated sub-systems that are responsible for controlling the details of a localized process. Product and process control are usually achieved by deploying feedback or feed forward control loops whereby key product and/or process conditions are automatically maintained around a desired set point.

To accomplish the desired product and/or process tolerance around a specified set point, specific PLCs are employed in the field and proportional, integral, and/or derivative settings on the PLC are tuned to provide the desired tolerance as well as the rate of self-correction during process upsets.

"PLCs are typically microprocessor- or computer-based devices that are used extensively to control industrial equipment or processes. Communications over DCS or PLC networks need to be more reliable and function at higher speeds 'compared to the long-distance communication systems used by SCADA systems' because of the process control functions of DCSs."[2]