DCS architecture: Block diagram:
Explanation: In DCS equipment is separated in functional area and is installed in different work areas of a process plant. The plant operator monitors and manipulates the set-points of the process parameter from central control room.
Controlling portion of the DCS, distributed at various locations performs following two function at each location.
1. Measurement of analog variable and discrete inputs
2. Generation of output signals to actuators that can change process condition
In Figure above the operator console in the control room is connected through a data highway to several distributed system components.
A DCS consist of the following modules:
1 Operator stations that use microprocessor based CRT display and keyboard communication with control device and displays
2 Remote multifunction microprocessor based controllers (PLCs)
3 A digital data link (data highway) that connects the multifunction controllers with the central operator stations.
The first priority of DCS is to provide operator interfacing and real time process control. DCS has flexibility of implementation of sequential control and integration among the various types of control.