RTU

Hi I am new in PLC. Could anyone tell me about RTU? How they are diferent from PLC/DCS?

Anymore there is little or difference between them.

Motorola manufactures PLCs which are also RTUs.

Stick a PLC on a mountain top to monitor a tank level, couple it to a radio to send the data to a host and you have a RTU. There are RTU protocol issues which are different from PLC communications. You should look up RTUs on the internet.

MJH

In the past, an RTU (remote terminal unit) was generally used for data acquisition from a remote site and occasionally had some control functionality. Often but not always, this control was a contact closure to enable or disable a motor and was manually initiated by an operator at a distant control center rather than by internal logic. The crux of the distinction between a local controller (PLC etc) and an RTU was the comms functionality.

The distinction is no longer so important. PLCs now offer a variety of comms options, remote I/O is available for most everything, many general purpose RTUs have IEC 61131 logic embedded, DCS nodes can be connected at a distance, OPC has matured. Virtually any of the control options can now be used in an RTU application.

There are still some application-specific RTUs out there to interface control systems to remote sites that have special systems. A classic example is tank farm management, where an RTU may be required to interface a unique inventory system to a balance of plant DCS or PLC network.