Saturday, 26 March 2011

Comparison with other control systems

RTUs, PLCs and DCS are increasingly beginning to overlap in responsibilities, and many vendors sell RTUs with PLC-like features and vice versa. The industry has standardized on the IEC 61131-3 functional block language for creating programs to run on RTUs and PLCs, although nearly all vendors also offer proprietary alternatives and associated development environments.

In addition, some vendors now supply RTUs with comprehensive functionality pre-defined, sometimes with PLC extensions and/or interfaces for configuration. See the MultiSmart pump station manager for a water/wastewater example.

Some suppliers of RTUs have created simple Graphical User Interfaces GUI to enable customers to configure their RTUs easily. Some examples are MoxGRAF from MOX Products for their MX602 Field Controller and PC-Link from Promosys Technology for their RTU-1, RTU-3 and RTU-8.

In some applications dataloggers are used in similar applications.

A programmable automation controller (PAC) is a compact controller that combines the features and capabilities of a PC-based control system with that of a typical PLC. PACs are deployed in SCADA systems to provide RTU and PLC functions. In many electrical substation SCADA applications, "distributed RTUs" use information processors or station computers to communicate with digital protective relays, PACS, and other devices for I/O, and communicate with the SCADA master in lieu of a traditional RTU.

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