How to overcome EMI in industrial automation
Industrial plants are facing more electromagnetic interference (EMI) due to rise in adoption of automation. Megan Ray Nichols offers a few tips to overcome them.
Industrial automation is experiencing a major shift as new technologies make industrial data-collection and automation more efficient and comprehensive than ever before. However, this technology also poses new problems for industrial plants.
With the adoption of these devices, factories and industrial plants are facing more electromagnetic interference (EMI) than at almost any point in the past. As a result, plant design that minimises EMI is more important than ever.
Here is how engineers and industrial designers can overcome EMI in industrial automation as the factory becomes more connected than ever before.
Difficulties of EMI in modern industrial automation
EMI is caused when the radio-frequency spectrum emitted by one electronic device disrupts or hampers the function
of another electronic device. Most pieces of factory machinery can cause EMI - like arc welders, live wires and just about any device with circuits and switches. The proliferation of personal wireless communication devices - mostly smart phones - also creates additional EMI.
Over time, EMI can degrade the function of any electric device — making it less efficient, its readings less accurate or causing permanent damage. In some cases, EMI can also cause total failure of these devices. If left unchecked, EMI can effectively render a plant's data-collection and automation operations more noise than signal.
As a result, industrial designers and engineers need to be aware of how EMI is created. They need they also need to know what techniques they can use to beat it.
Limiting the effects of EMI with plant design
Plant managers can help ensure that as few devices as possible are exposed to EMI with the right plant design and cable organization.
In general, simple techniques that reduce EMI. Things like wire grounding and shielding, amplifiers, twisted pair wires and differential EMI filters can be functional solutions to EMI in many plants. There are, however, additional steps that plant designers can take to make sure that EMI won't become a problem in the future.
Power wiring and instrument wiring should generally be run in separate conduits or cable, or be otherwise shielded from each other. If power wiring and instrument wiring must cross, make sure they do at a 90-degree angle. This minimises the interference the two cables will have upon each other.
Bad grounding and shielding of devices and sources of electricity, like power lines, can cause significant EMI. Network wiring, like ethernet cable, should be screened. Unscreened network cable is primarily designed for consumer and office use and is only suitable for environments with little risk of EMI. Leaving your network cable unscreened can degrade the quality of your readings over time.
Cable screening should also be terminated at both ends, even if having both screens would create a ground loop. Leaving the screen disconnected at one end can lead to high-frequency EMI leaking or escaping from that end.
Similarly, consumer-grade IoT devices frequently fail EMI testing
due to their reliance on pre-certified RF modules, and are probably not suitable for factory use. EMI failures can be avoided with good design
, but not all manufacturers take these steps. Industrial IoT devices are more likely to be EMI shielded and produce less EMI. However, you shouldn't count on a given IoT device being properly designed, even if it was built for industrial applications.
Other strategies for overcoming EMI
EMI software or a network analyzer can help identify possible sources
of EMI. The software can also verify if error or device failure results after exposure. Traditional methods of collecting data about EMI — analogue tools and paper records — can also be useful in identifying edge cases or verifying EMI. However, these methods probably won't work as a complete or long-term solution since EMI becomes a bigger problem and there are more sources for interference.
Other software platforms, like permanent network monitoring systems can provide even more robust solutions. These platforms can effectively use existing data-collection infrastructure of a plant to monitor interference. The platform will alarm managers or engineers about irregularities that cross a specified threshold.
Both of these systems will likely allow for the long-term storage of EMI data. It may include its own analytic software or algorithms to help engineers spot patterns in EMI. This will allow engineers to build better understanding of what may be causing EMI in a plant.
With either solution, plant engineers can use devices likely to cause EMI — IoT sensors and other monitoring devices — to effectively monitor themselves and other factory equipment. This can help to ensure that plant managers have minute-to-minute data on their systems and allow them to rapidly respond to EMI once detected.
Protecting industrial automation from EMI
The rapid adoption of new technologies has made the problems caused by EMI more serious than ever for plant managers.
EMI can reduce the effectiveness of automated systems, making it harder for plant managers to collect accurate and consistent data from IoT devices and sensors.
Fortunately, many simple techniques - like proper cable and IoT devices shielding - can significantly reduce EMI exposure for critical automation systems.
About the author
Megan Ray Nichols is an international STEM (science, engineering, technology and math) writer & blogger. She has built up a name for herself in the last three years by running a blog, "Schooled By Science", and writing for sites like IoT Times and Manufacturing.net. She can be reached on email: firstname.lastname@example.org or https://schooledbyscience.com/