PLC AND DCS

Not to be confused with machine control

PLCs can range from small "building brick" devices with tens of inputs and outputs (I/O), in a housing integral with the processor, to large rack-mounted modular devices with a count of thousands of I/O, and which are often networked to other PLC andSCADA systems.They can be designed for multiple arrangements of digital and analog I/O, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact. Programs to control machine operation are typically stored in battery-backed-up or non-volatile memory.

A distributed control system (DCS) is a computerisedcontrol system for a process or plant usually with a large number of control loops, in which autonomous controllers are distributed throughout the system, but there is central operator supervisory control. This is in contrast to non-distributed control systems that use centralised controllers; either discrete controllers located at a central control room or within a central computer. The DCS concept increases reliability and reduces installation costs by localising control functions near the process plant, with remote monitoring and supervision.

PLC

      Prosoft
Schneider Modicon             Bachmann
GE                                         Woodhead
Siemens

DCS

ABB HIMA
Invensys Foxboro               Yokogawa
Invensys Triconex               Honeywell
Westinghouse Emerson
Woodword