RTUs

An RTU, or remote terminal unit, is a field-deployed, microprocessor-based device that interfaces sensors and actuators with a supervisory control and data acquisition (SCADA) system. RTUs perform data acquisition, local processing, and remote control, enabling centralized monitoring and command of distributed equipment.

In operation, RTUs collect measurements such as voltage, current, pressure, and temperature from field devices, time-stamp and format the data, and transmit it to the SCADA master. They can also execute local control actions, such as opening or closing valves and switching circuit breakers, under predefined logic or operator commands. Alarm and event handling are common capabilities.

Typical RTU hardware includes analog and digital input/output interfaces, communication ports (serial, Ethernet, cellular, radio), a power supply, and a rugged housing suitable for harsh environments. They are designed for remote locations and may be powered from AC or DC sources, with battery or solar backups to ensure operation during outages.

RTUs communicate using standard industrial protocols such as DNP3, IEC 60870-5 (101/104), and Modbus (RTU or TCP). Some RTUs support time synchronization, data buffering during communication outages, and cybersecurity features to reduce the risk of unauthorized access.

RTUs are commonly used in utilities, water and wastewater, oil and gas, and transportation applications, as components of SCADA systems for monitoring and controlling remote assets. They are often contrasted with programmable logic controllers (PLCs), which are typically used for localized, high-speed control tasks rather than remote supervision.