DCS and PLC

[Buchi]

Hi guys,
can somebody explain to me in a very simplistic language the meaning of DCS (distributed Control system) and PLC(Programmeable Logic Control) as applied to plane design.

Buchi

 

[Buchi]

Sorry for the error. i meant "plant design" not "plane design" Buchi

 

[JOM]

Hello Buchi,

In essence, I would say it is a difference in architecture.

The vast majority of installed PLC's are "stand alone" units control a collection of machinery.

A DCS is a collection of standalone controllers (often PLC's) that are linked back to a central operator control station. "Distributed" means that the control logic is installed in the stand alone units. If the comms link to the central control, station fails, then the stand alone unit continues with its control functions.

Does that make sense?

John. Cheers,
John.

 

[svanels]

I would rather say that a Distributed Control System has a collection of PLC's among other things.

A PLC, Programmable Logic Control is a device that measures a process variable, compares it with a setpoint and adjust some controlling device.
A simple PLC is the thermostat of a refrigerator. It measures the temperature, and stops the compressor if necessary and/or measures the thickness of the ice in the freezer. Doesn't require much human intervention.

A Distributed Control System exist of a collection of control and measuring devices, (sensors, valves, plc's etc.), a high speed network, human intervention stations (control room), lan and wan support, an information management system (often a relational database managent system), safe guard systems (process computers which take over in certain conditions) and can be used in applications ranging from machine control to total industrial plant automation.

Regards

Steven van Els
SAvanEls@cq-link.sr