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emc basics


By the way - What is EMC?

EMC - a definition

EMC means nothing more than "an electronic or electrical product shall work as intended in its environment. The electronic or electrical product shall not generate electromagnetic disturbances, which may influence other products". In other words, EMC deals with problems of noise emission as well as noise immunity of electronic and electrical products and systems. Electromagnetic disturbances occur as conducted interference as well as radiated emissions and immunity problems.

Generally EMC, Electro Magnetic Compatibility, should really not be difficult to understand, but as you know, the devil is in the details. Let us explain the topic in a little bit more details. For those of you who are EMC-experts, we hope you excuse us for making some "non-scientific" simplifications.
The word EMC does not include the influence of electromagnetic waves (either desired or undesired) on biological systems. This is a much larger field and is covered by the expression "EMCE" ("E" is for environmental), which is not the topic here and is also not the field in which EM TEST works.


Where EMC got started

The history of EMC

Let us go back in the history of EMC. EMC is older than you may believe.

We are all living with our history. The same is for EMC. You may not know, as many EMC experts also do not know, how everything was started. We want to give you a short summary of the history of EMC in Europe. The following is not given in great detail, but it does illustrate why we are where we are today in the EMC world.

The new age of communication in Europe began 1892 when the German Parliament voted to create the "Law of Telegraph in the German Empire". This was the first law in the world that dealt with influences of electromagnetic disturbances on products and installations in the field of telegraph technique. This law also regulated the procedures to be followed in case such electromagnetic disturbances were found. People at that time had discovered very quickly that cables did disturb each other. The disturbances on telegraph and telephone communication were the most severe. The German Society of Electrotechnicians, founded in 1893, was the foundation of what today is well known as VDE. Wilhelm von Siemens was one of the original founders of this famous society.

More than 110 years ago EMC was not a big matter but this was changed immediately in the evening of December 22 in 1920. On this night, the radio station of König Wusterhausen southeast of Berlin broadcasted the Christmas concert of the German mail officials. The concert was a live event and the audience included the German Chancellor Hermann Müller, who was close to the concert location in the famous castle of König Wusterhausen. The Chancellor was not very amused by the electrical noise interference generated by vehicles passing by and he gave strict orders to immediately prevent such disturbances. The hour of "Radiated Emission" had come and was then later on called EMC.


EMC standardization in the past

The first steps towards standardization ...

Germany was among the first to recognize the need to prevent and solve the problems of radiated emissions. In 1933, the international committee for radiated emissions, better known as CISPR was founded. Late in the 60's, concrete investigations were made to deal with the immunity of electrical products. In 1973 the International Electrotechnical Commission, the IEC, founded the technical committee TC77 whose function is to develop standards related to EMC.

In the 2nd World War knowledge of electromagnetic waves and their ability to create disturbances was used. During the war, radar technology was developed. Not only did the new communication technologies of radio, television and telephone require electromagnetic compatibility, they were the driving force in changing from tube technology to transistors. The evolution of highly integrated chip technologies requires a broad understanding and use of EMC design experience.

As the technology progressed, legislation and standardization was developed to insure the harmony of the new sciences from an EMC standpoint.

Lets go back again to the German example. In 1927 the first edition of the "Deutsche Hochfrequenzgerätegesetz" was published. The recommendations of Chancellor Müller were successfully introduced although it took about 7 years to result in an official law. The new law was revised several times and was matched to the technical progress. This law was valid until December 31 of 1995 and was then replaced by the German EMC law, which is based on the European Directive.


... and today

Every product's reliability depends on EMC

No electrical product or installation can be designed seriously unless all aspects of EMC are taken into account. This is not only important for common products such as radios, television sets, computers, telephones, washing machines, etc., but it is also especially important for complex products such as vehicles, aircraft, ships and large industrial installations. These are very sensitive to EMC problems and no one wants to accept serious disturbances within a big chemical plant.

Because of all the efforts made and being made to insure EMC compatibility, people start to believe that, after a certain time, all products are safe and immune. Sorry, but this has not come true as yet. Each new generation of engineers and technicians are again challenged by the issue of EMC with each new product and within each new installation. Practical solutions to EMC problems are not taught at universities. This can only be achieved with many years of experience in the field and testing. This is where EM Test can be of help.

EM Test has the task of educating engineers and technicians about EMC. EM Test can use its EMC experience to help all. Remember how this very interesting technical field began and developed. Only those who know the sources, and our sources are the basics of EMC, know where he has to go. We know the issues from the very beginning and will support you so that you better understand them. Let's go together a part of this way and let's keep in contact. By reading this message you have completed the first step.

Diethard E.C. Möhr

Siemens AG,
Manager of the Referat EMV, Erlangen/Germany
Secretary of IEC TC77 EMC



EMC - What it is

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