Remote Terminal Unit | Microprocessor-Controlled Device

Remote Terminal Unit

A Remote Terminal Unit (RTU) may be a Microprocessor-Controlled device that Interfaces Objects within the Physical World To A Distributed system Or SCADA (Supervisory management And data Acquisition) System By transmission measurement data To A Master System, And By exploitation Messages From The Master superior System to manage Connected Objects. alternative Terms which will Be Used For RTU Is Remote measurement Unit Or Remote Telecontrol Unit.

System Architecture

An RTU monitors the field digital and analog parameters and transmits information to the Central observation Station. It contains setup software system to attach information input streams to information output streams, outline communication protocols, and troubleshoot installation issues.
An RTU might incorporates one complex circuit card consisting of varied sections required to try and do a custom fitted operate or might incorporates several circuit cards as well as central {processing unit|CPU|C.P.U.|central processor|processor|mainframe|electronic equipment|hardware|computer hardware} or processing with communications interface(s), and one or a lot of of the following: (AI) analog input, (DI) digital (status) input, (DO/CO) digital (or management relay) output, or (AO) analog output card(s).
An RTU would possibly even be a small method management unit with a small data Base for inflammatory disease, Alarming, Filtering, Trending functions then on complemented with some BASIC (programming language) tasks. because it is employed in pipeline, grid guarding systems or for instance within the part II project. Key in such environments it will operate below harsh conditions for instance from -50 to seventy degrees Celsius, switch its IO system solely on once required. for instance, it communicates via RS485 or wireless communication links in a very multi-drop configuration. during this style of configuration it’s a far off unit that collects information and performs straightforward management tasks. It doesn’t have moving components and uses extraordinarily low power and is usually star steam-powered.

Power Supply

A kind of power provide are going to be enclosed for operation from the AC mains for varied processor, standing wetting voltages and alternative interface cards. this might accommodates AC to DC converters wherever operated from a station battery system.
RTUs may include electric battery and charger electronic equipment to continue operation in event of AC equipment failure for important applications wherever a station battery isn’t obtainable.

Analog Inputs

A RTU will monitor analog inputs of various varieties together with 0-1 mA, 4–20 mA current loop, 0–10 V., ±2.5 V, ±5.0 V etc. several RTU inputs buffer larger quantities via transducers to convert and isolate globe quantities from sensitive RTU input levels. AN RTU can even receive analog knowledge via a communication system from a master or IED (intelligent electronic device) causing knowledge values to that.
The RTU or host system interprets and scales this data into the acceptable units like amount of water left, temperature degrees, or Megawatts, before presenting the info to the user via the human–machine interface.

Digital(Control Relay) Outputs

RTUs might drive high current capability relays to a digital output (or “DO”) board to modify power on and off to devices within the field. The DO board switches voltage to the coil within the relay, that closes the high current contacts, that completes the ability circuit to the device.
RTU outputs might also consist of driving a sensitive logic input on an electronic PLC, or different device using a sensitive five V input.

Analog Outputs

While not as normally used, analog outputs could also be enclosed to regulate devices that need varied quantities, like graphic recording instruments (strip charts). Summed or processed knowledge quantities could also be generated in a very master SCADA system and output for show regionally or remotely, where required.

Software and logic Control

Modern RTUs are usually capable of executing easy programs autonomously while not involving the host computers of the DCS or SCADA system to change readying and to produce redundancy for safety reasons. an RTU in a fashionable water management system can usually have code to change its behavior once physical override switches on the RTU are toggled throughout maintenance by maintenance personnel. this can be done for safety reasons; a miscommunication between the system operators and therefore the maintenance personnel might cause system operators to mistakenly modify power to a pump once it’s being replaced, as an example.
Maintenance personnel ought to have any instrumentality they’re performing on disconnected from power and fast to stop harm and/or injury.


A RTU is also interfaced to multiple master stations and IEDs (Intelligent Electronic Device) with completely different communication media (usually serial (RS232, RS485, RS422) or Ethernet). an RTU could support normal protocols (Modbus, IEC 60870-5-101/103/104, DNP3, IEC 60870-6-ICCP, IEC 61850 etc.) to interface any third party package.
Data transfer is also initiated from either finish exploitation varied techniques to insure synchronization with least information traffic. The master could poll its subordinate unit (Master to RTU or the RTU poll associate degree IED) for changes of information on a periodic basis. Analog worth changes can typically solely be reported only on changes outside a group limit from the last transmitted worth. Digital (status) values observe the same technique and only transmit teams (bytes) once one enclosed purpose (bit) changes. Another methodology used is wherever a subordinate unit initiates an update {of information|of knowledge|of information} upon a planned amendment in analog or digital data. Periodic complete information transmission should be used sporadically, with either methodology, to insure full synchronization and eliminate stale information. Most communication protocols support each ways, programmable by the installer.
Multiple RTUs or multiple IEDs could share a communications line, in a multi-drop theme, as units ar self-addressed uniquely and only answer their own polls and commands.

IED Communications

IED communications transfer data between the RTU and an IED. this may eliminate the necessity for several hardware standing inputs, analog inputs, and relay outputs within the RTU.
Communications are accomplished by copper or fiber optics lines. Multiple units might share communication lines.

Master Communications

Master communications are usually to a bigger system in a control room or a data collection system incorporated into a bigger system. data is also moved using a copper, fiber optic or radio frequency communication system. Multiple units could share communication lines.


• Remote observation of functions and instrumentation for:
• Oil and gas (offshore platforms, onshore oil wells, pump stations on pipelines)
• Networks of pump stations (waste water assortment, or for water supply)
• Environmental observation systems (pollution, air quality, emissions monitoring)
• Mine sites
• Air traffic equipment like navigation aids (DVOR, DME, ILS and GP)
• Remote observation and management of functions and instrumentation for:
• Hydro-graphic (water provide, reservoirs, waste systems)
• Electrical power transmission networks and associated equipment
• Natural gas networks and associated equipment
• Outdoor warning sirens
• The part II project

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