Basic standards - the basis of standardisation's food pyramid
Standards are technical documents that establish procedures and technical requirements, for example, for the execution of EMC testing with electrical disturbance. When technical developments in society change the electrical environment, the standards and requirements keep up and take into consideration new sources of electrical disturbance, for example such as the widespread presence of wireless products or highly efficient switch-mode power supplies for LED lighting. An international group of experts are writing the new basic standards.
IEC´s technical committee 77 is responsible for standards relating to ElectroMagnetic Compatibility (EMC). In other words, the electromagnetic co-existence of electrical appliances in the environments in which they are used. Sub-committee SC77B works specifically on high frequency related EMC phenomena, such as radio waves. The working group WG10 is responsible for writing new standards when new electrical disturbances arise. This article is written by the group’s secretary.
Some time ago the working group WG10 was asked to write a new standard for “Radiated fields in close proximity”, which deals with field radiation from transmitters located very close to electronic products. Such transmitters can be RFID, mobile telephones, WiFi and similar devices. The standard, which is called IEC 61000-4-39, deals with testing with fields emitted from transmitters that are at distances of 200 mm or less from other products.
The technical preliminary work has shown that even though EMC testing with powerful fields of 100 V/m or 200 V/m is carried out in accordance with the existing standards, these electronic products are affected differently if the source of the field is very close to the product. This means that a new standard test is required at a distance of 100 mm ± 5 mm.
Very special antennas in the form of a TEM horn and a more meticulous procedure have been designed to be able to establish the test method. The aim is to achieve the best possible reproducible test, so that it can be repeated anywhere in the world without leading to diverging results. An example of the test setup is shown in Figure 1.
The first version of the standard IEC 61000-4-39 is now approved, and in the coming years it will go through a “stability period”, during which time it cannot be altered.
WG10 experts are currently working on updating the ‘old’ standard for field radiation: IEC 61000-4-3. This work will continue at the group’s next meeting in Pisa, in calendar week 19 in 2017.