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now routinely specified for industrial processes as then send this data for storing, trending, analyse
businesses gain a better understanding of their and action. Sensors are simpler devices, which
benefits. In these applications, the RTU connects to means they are not designed to interpret protocol
a plant control room or SCADA, providing a low communication on their own like RTUs. That’s why
latency response to changing process conditions as RTU’s play a crucial role in digitising the inputs
well as performing data filtering. They ensure that from sensors into protocol format and transmitting
only key, critical information is passed securely via them to SCADA. The SCADA then issues control
the narrow communications links, minimising data commands back to the RTU which in turn transmits
throughput but maximising useful information electrical signals to control relays.
received. The single biggest advantage of an RTU
RTU’s are widely used in the industrial sector for compared to a PLC is that the environmental
process automation and control as part of a robustness of the former makes it the stand-out
supervisory control and data acquisition (SCADA) choice for demanding industrial and manufacturing
system. Effectively, RTU’s are mini-computers that applications.
collect data locally, act upon it immediately, and RTU’s can be used in locations with extreme
report securely to the central control room, whilst climatic temperatures and/or remote locations that
maintaining a local historical store as an additional are off the power grid. For instance, Kingfisher
backup. RTU’s have been selected as high availability
RTU’s collect these additional data points from process controllers with extensive communications
a vast range of individual pieces of equipment. For capabilities for sites with temperatures ranging from
instance, new data points may replace manual dips -40C to +85C.
tests to verify the accuracy of primary level sensors, Their resilient and secure nature, combined with
track product density to ensure that the right independent communications links, redundant
product is in the right vessel or monitor product power supplies and redundant process controllers
temperatures, inert gas blanket supply and pump make them an extremely robust solution in these
vibration. There are benefits for engineers applications.
overseeing remote sites that are vulnerable to theft Again, RTUs can perform autonomous control in
and vandalism, too. The opportunity list is virtually real time and then report to SCADA that it has
endless. everything under control. Engineers at the SCADA
interface can ‘supervise’ the operations by setting
Key differences new KPIs (Set Points) or updating instructions
The main difference between an RTU and PLC is (open/close this, start/stop that, for example) for
that the former is highly suitable for assets spread RTUs to then act upon and manage locally.
over wide geographic areas because they use
wireless communication. PLCs can be better suited Can RTUs facilitate IIoT?
to local controls, although there is now much There has been a significant improvement in RTU
overlap in functionality between the two and cost processing power and memory recently, which is
effectiveness of latest RTU’s mean they are often helping facilitate Industrial Internet of Things (IIoT).
used for ‘near’ location assets. A significant area of opportunity is the ability of IIoT
RTUs, the field part of a SCADA system, are to create smart assets, even those that are part way
used to translate the physical world into digital and through their lifecycle. For example, deploying

November 2020 • INDUSTRIAL TECHNOLOGY EXTRA • p11