welcome to minuteprofinet in today's video i will explain one of the most dramatic evolutions
in industrial automation the transition from 4 to 20 milliamps
to digital field buses we will compare the two and highlight key benefits and new business
models that arise from the use of field buses for those of you new to the channel welcome
my name is michael bowne and i'm a part of profibus profinet north america a non-profit
member supported organization we aim to promote and educate the public on industrial automation
and networking technologies so if you like learning about manufacturing and automation please
feel free to subscribe to our channel but for now let's go to the whiteboard
what are the differences between 4 to 20 milliamps and digital field buses
how and when did the transition occur the factory floor has evolved dramatically over the years
the first manufacturing facilities did not rely on any automated controls all
processes were based on manual operation the first automated controls were pneumatic
pneumatic pressure controls move pressurized or compressed air signals from a controller to
a device through copper or plastic tubes after the adoption of pneumatic controls electronic
controls were introduced the 4 to 20 milliamp convention was born in the 1950s as electronics
became cheaper and the reliability met the automation industry's requirements 4 to 20
milliamps provided a low low-cost easy to use solution not subject to major signal line losses
automation logic was accomplished using relays until being replaced by plc's running relay ladder
logic in code the invention of the first plc in 1968 simplified automation network substantially
and reduced hardware requirements in the 80s and 90s several organizations and device manufacturers
started engineering the first field buses like for example profibus field buses enabled two-way
digital communication in a fieldbus network the devices are an integral part of the system
from the engineer's point of view there is no distinction between the devices and the control
system it is an integrated hole but why was the transition from 4 to 20 milliamps to field buses made?
4 to 20 milliamps has some limitations and disadvantages when compared to field buses
here's an example of a 4 to 20 milliamp application with one controller and field
devices each analog signal indicates a precise value for temperature pressure
or voltage for example the values are exact and infinite between 4 and 20 milliamps but there are
some challenges with this for example individual cables and wires are required for each device
troubleshooting can be slow due to the lack of diagnostic information
and signals are prone to unwanted noise interference analog signals require wiring
from the controller to each device the wiring costs for a complete project can be costly also
it can be challenging to commission and maintain complex and extensive cable infrastructures
troubleshooting can also be a difficult task with 4 to 20 milliamps analog connections do
not provide extensive diagnostic information some devices might have diagnostic capabilities but
might not be comprehensive equipment on the factory floor produces electrical noise
analog signals are more susceptible to interference which can affect process accuracy
and reliability using twisted shielded cables can lower the effects of noise on electrical signals
but it is not a bulletproof solution nor is it cost-effective for any number of reasons
some automation facilities still rely solely on 4-20 milliamp signaling but many network
installations have migrated to digital field buses due to the value propositions field buses
offer additional functionality and tackle many limitations of 4 to 20 milliamp communication
an essential advantage of field buses is connecting multiple field devices over a signal
cable or bus in fieldbus networks distributed io mechanisms collect or distribute multiple
inputs and outputs from the field into a local io device then the data is transferred through just
one cable to and from the plc this factor alone can significantly cut engineering installation
commissioning and maintenance costs digital signals can carry more information per second
than analog signals they can provide diagnostic information for all the devices in the network
that information is not only useful to resolve downtime situations but also prevent them
network diagnostic information is used for preventative and predictive maintenance practices and other
advanced asset management techniques signal noise can interfere with both analog and digital signals
however the amount of noise necessary to affect a digital signal is much higher digital field
buses can withstand higher exposure to electrical noise without compromising data and communication
quality modern automation facilities require the speed accuracy and versatility of field buses
the greater accuracy of digital means significant improvements in production speeds and quality
field buses deliver real-time performance for automation environments and with the
shift from analog to digital we now have a network and different topologies are possible
each fieldbus standard offers specific characteristics
profibus was introduced in the early 90s by PI, currently it is the leading fieldbus
technology in terms of functionality and adoption by 2019 there were over 62 million profibus nodes
installed worldwide today the trend continues with industrial ethernet standards such as profinet
higher bandwidth larger message sizes and address spaces are some benefits plus multi-protocol
coexistence enables modern network architectures and connections to higher level systems
i hope you found this information helpful to learn more about field buses and profibus specifically
we've created a detailed slide set with technical diagrams and descriptions
you can download it for free by following the link in the description of this video also please visit
our website at us.profinet.com to learn more about the profibus and profinet technologies feel free
to comment below share your feedback and ask any questions and as always thank you for watching