Thread Starter


As something of a newcomer to the Automation world I have a little
experience and training with PLC's, Allen-Bradley and Mitsubishi. I have
seen these terms used but am curious to their meaning and differences,
SCADA - Supervisory Control And Data Acquisition
SCADA is usually a software package that allows for supervision, control, data acquisition (funny how that works huh?)on a PC (sometimes at a remote site or control room). It's a means to interface to a PLC, perform data
logging, give a graphic operator control application, and more.

PLC - Programmable Logic Controller
PLCs are programmable controls similar to computers, but instead of a
keyboard and mouse, they have discrete and analog inputs and outputs. They
are more industrially hardened and rugged than computers, and have a more
specific dedicated function.

RTU - Remote Terminal Unit
Sometimes a PLC, sometimes a special device, RTUs are basically remote
terminals on a control system. Typically they connect over a modem or other
intermittent means. One example would be a controller on the side of a
water tower, where it is communicating back to the water authority at another site over a dial-up modem as neccessary.

These are basic descriptions, and I'm sure that some may disagree with my
definitions, so anyone who wants to elaborate, go for it!