Likewise, after solving the algorithm, the RTU has to communicate with the different actuators in the field. This requires a defined form of communication between the RTU and the various sensors in the field. This way, the RTU enables the field processes near it to operate according to design.īefore the controller in the RTU can solve the algorithm, it has to receive an input from the field sensor. The entire system works together based on wiring or some form of communication protocol. Sensors measure the process variables, while actuators adjust the process parameters and controllers solve algorithms for controlling the actuators in response to the measured variables. Therefore, they make sure of the reliability of detection for safety related functions. Regulatory agencies certifying RTUs prefer use of dedicated hardware for solving certain safety related functions such as toxic gas concentration and smoke detection. As scan periods in RTUs are very small, the entire activity happens very fast, hardly taking a few milliseconds, with the RTU repeating the process. By solving the algorithms in it using the input signals, the RTU then sends out control instructions to valves or other control actuators. Sensing devices or sensors gather data from the field, sending the signals back to the RTU. Present RTUs are powerful computers able to solve complex algorithms or mathematical formula describing external functions. Likewise, they can program algorithms for logic solvers, power factor calculators, flow totalizers, and many more, according to actual requirements in the field. Users program controller algorithms into these units, allowing them to control sensors and actuators.

Nowadays, small computers make up remote terminal units or RTUs and SCADA units.

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