PLCs and RTUs

Programmable Lagic Controllers (PLCs) and Remote Telemetry Units (RTUs) used to be distincly different devices but over they time they are now almost the same. This has been a convergence of tecnology as manufactures of these devices exlanded their capabilities to meet market demands.

If we go back 30 years, an RTU was a 'dumb' telemety box for connecting field instruments. The RTU would 'relay' the data from the instruments to SCADA host without any processing or control bud had well-developed communication interfaces or telemetry. In the 1990s control programming was added to the RTU so it operated more like a PLC. PLCs on the other hand could always do the conteol program but lacked communication interfaces and data logging capability, which has been added to some extent over the past decade. 






SCADA Systems
SCADA Field INstrumentation
PLCs and RTUs
Remote Communications Networks
SCADA Host Sofware

A futher development of devices in the field is to offer a specific application that could incorporate a number of instruments and devices with an RTU/ PLC, incorporating technology sets to provide an 'off the shelf' approach to common process requirements, e.g gas well production that includes elements of monitoring, flow measurement and control that would extend as an asset into the SCADA Host.

In terms of environmental nd regulatory compliance, PLCs and RTUs have the same type of requirements as instrumentation in that they operate in the same environment. HOwever, PLCs have traditionally not been as environmentally operate in areas m such as factory floors, where the environment was already conditioned to some degree.

From: sina.com.pk

Source: Retyped From SCADA Systems White paper (Mrch 2012) by Schneider Electric Tekementry & Remote SCADA Solutions

SCADA Security
Conclusion of SCADA 
About Slave-to- Slave Messaging SCADA
Programmable Logic Controllers (PLCs)
Terminology of PLCs