Can someone Explain to me what an RTU is?

What is a remote terminal unit?

Googleing provided information about it being a microprocessor controlled unit and also paraphrased something along the lines of being a Less powerful option vs a plc, but it is still unclear to me.

Why wouldn't I just use a remote I/O block with my PLC?

Does it replace a PLC or is it like remote I/O?

What are common good name brands for RTUs?

Any general information would be appreciated.

Remote Terminal Unit

https://en.wikipedia.org/wiki/Remote_terminal_unit

RTU is a generic term. We use a lot of different types of RTUs, some are PLC based, some are just remote I/O. For radio based RTU units with simple devices at the other end (like water pumps), my favorite is the Phoenix Contact TWE series radios with I/O modules. I just use Modbus messages from a master PLC to monitor and control the I/O modules we add to the remote radio.

We have used Micrologix 1100 or 1400 as RTU controllers as well as Click PLCs with a variety of different radio modems...Maxon UHF, Nanostations, Digi, Phoenix, Calamp, Freewave, whatever the customer has already is often the deciding factor.

We also have a bunch of RFScada applications which are pretty reliable but limited in functionality compared to a PLC.

In the old days, they are "more" different than a PLC. These days, there aren't too many differences. RTU now describe a function than actual hardware difference. It can even be Windows based PC running a communication program.

Generally speaking, RTU tend to have more communication ports and protocol than a PLC. But I tell folks is to find out the issue they are trying to solve then pick the best tool to do that job.