What is the difference between a PLC and an RTU?
In terms of a water utility, the terms PLC and RTU are almost interchangeable. Generically, an RTU or Remote Terminal Unit is the entire unit tasked with collecting status signals and outputting control commands. This would include power supplies, communications devices and the enclosure itself. The PLC (Programmable Logic Controller) is the intelligence of the RTU. It should be noted that the definition above ignores off the shelf RTUs. Some vendors market a product as an RTU. In this case, the RTU is primarily the intelligence and data interface modules. It may be a standalone unit or it may be integrated as one component of the unit. In this case you might have an RTU within an RTU. The majority of water systems utilize a PLC as the basic intelligence in the RTU.
