Basics of electromagnetic compatibility

Table of contents

• The history of EMC
• Basic concepts
• Brief excerpt of the EMC standards
• Conclusion

The history of EMC

From 1800 to today

The problem of electromagnetic incompatibility has existed since the beginning of electrical engineering. However, the term EMC is only 40 years old. Optical telegraphy was replaced by electrical telegraphy around 1800. With the laying of the first submarine cable in the mid-19th century, long-distance communication using coded signals became possible. Direct lightning strikes or interference voltages from thunderstorms posed a problem, but even then, this could be solved with devices such as surge arresters. Telegraphy was very time-consuming and was constantly being developed further. There were typed telegraphs with letter keyboards and teleprinters capable of transmitting messages in written form.

At the end of the 19th century, the previously unpopular telephone became widely available. Alexander Graham Bell founded the Bell Telephone Company in 1877, which was renamed the American Telephone and Telegraph Company (AT&T) in 1885. At that time, telegraphy and telephony were based on "single-wire" technology. With the introduction of the public power grid around 1900, this technology had to be abandoned. Until then, the earth had been used as the return conductor, which was subject to excessive interference from arc lamps in street lighting and other sources.

Another milestone in electrical engineering was the spread of radio technology. Initially used by the Imperial Navy to send wireless telegrams, it soon became widely known in the form of radio broadcasts (1930). Even then, attempts were made to mitigate interference and the International Special Committee for Radio Interference (CISPR) was founded. During World War II, the number of electronic devices increased rapidly, causing them to interfere with each other. Safe operation was no longer guaranteed. It was quickly recognized that not only the source of interference, but also the immunity of devices played an important role.

In the mid-1960s, consumer electronics boomed. Color television using the PAL system was introduced in Germany. For cost reasons, manufacturers chose plastic housings, which naturally lacked shielding. Due to the ever-increasing number of devices, interference also increased. There were no established standards that manufacturers could adhere to. Starting in the early 1980s, the Association of German Electrical Engineers established new regulations for emitted interference and immunity. The DIN VDE regulations have since been incorporated into the European standard system (the EN standards).

The development of these standards is far from complete. With the advent of ever-newer technology, the requirements continue to increase. As I already mentioned in my article "Medical devices in the Internet of ThingsAs I described in "Integrated Communication," the trend is toward networked devices that are continuously connected to the internet. Another trend is toward wireless communication and data transmission. Most devices today are connected to the internet via Wi-Fi. Wireless chargers enable wireless charging of smartphones, and NFC cards/chips are used to pay in cafeterias or to unlock front doors.

Basic concepts

Sources of interference There are various forms of interference. They all have one thing in common: the emission of electronic or magnetic interference. There are both natural and artificial sources of interference. Natural sources include atmospheric discharges and electrostatic discharges. Artificial sources of interference can be intentional (e.g., radio) or unintentional (e.g., frequency converters) and are emitted by other electronic devices.

Interference sinks are electrical devices or equipment that are Sources of interference Electromagnetic emissions can lead to signals being misinterpreted or amplifier inputs being overloaded, making further communication impossible. Interference sinks must have a certain Immunity to have Malfunctions to avoid.

There are three main Pathways of spread: conducted electromagnetic propagation, propagation via magnetic or electric near fields and via electromagnetic waves.

Brief excerpt of the EMC standards

The EMC standards are far too extensive to address every single point. Therefore, the goal is not to address each individual standard, but rather to provide a brief overview. The EMC standards are divided into the so-called Generic standards (EN 61000), in which Product standards and into the Test standardsGeneric standards are general and contain standards for immunity and emission. Product standards are specifically tailored to product groups. The following tables provide an overview of important standards.

Conclusion

EMC technology is a very broad topic (almost like black magic), which certainly cannot be explained in detail in a single blog post. I hope I've given you a brief introduction to the topic and piqued your interest. More articles will follow on this blog. Please leave me some feedback. I'll be happy to answer any questions you may have on this topic.

Best regards