IEC 61000-5-7: Degrees of Protection Provided by Enclosures Against Electromagnetic Disturbances (EM code)
The IEC 61000-5-7 testing standard details performance requirements for degrees of protection by empty enclosures against electromagnetic disturbances. The frequency range covered by the IEC-61000-5-7 tests is between 10kHz and 40GHz. The shielding performance of this testing is completed prior to equipment being installed in the components.
When working with an IEC 61000-5-7 test lab, the objective is to determine whether or not the enclosure provides adequate shielding of electromagnetic energy. Adequate shielding provides acceptable performance of the complete assembled units when tested to the applicable IEC standards. It is important to note that acceptable performance of an empty enclosure does not guarantee that the completed units will meet all of the EMC test requirements.
The objective of IEC 610000 5 7 testing is essentially to categorize enclosures by shielding performance. Enclosures can mean cabinets and sub racks. By providing categorization, manufacturers can determine which enclosures would be the best fits for their equipment. The requirements for immunity to various types of attenuating electromagnetic disturbances will need to be considered. These disturbances can be caused by lightning or high-altitude electromagnetic pulses (HEMP).
IEC 61000 5 7 test labs like Keystone Compliance are essentially testing the shielding effectiveness of an enclosure when testing to this standard. This testing is evaluating the ability of the shield to attenuate or reduce the external electromagnetic fields and surface currents before they reach the interior. Conversely, it might be necessary for the enclosure to reduce the electromagnetic fields produced by the internal equipment of the enclosure.
The most effective shielding material is metal. However, several other materials such as fabrics, resins and composite materials can also shielding properties. The most common reasons for enclosures to fail centers around enclosures. The two primary causes of penetrations are electrical and mechanical. Electrical can include alarms, antennas, cables, connectors, power and signal. Mechanical can be doors, pipes, vents and other mechanical openings. There are various ways of sealing penetrations, but the most common are gaskets and filters.
To complete the required tests in shielding effectiveness testing, two frequency sweeps must be conducted. The first sweep is completed when there is no barrier in place. This provides the shielding effectiveness test lab with a summary of all of the frequencies that are present. The second sweep occurs with the barrier in place. All strength of the signal received during the first sweep is compared to the strength of the signal received during the second. The strength is determined in decibels.
The IEC61000 5-7 test standard provides a number of definitions that assist with understanding the testing. Below are some of the more prevalent terms used:
Degree of protection: This is defined as the extent of protection provided by an empty enclosure against the passage of electromagnetic energy from external to internal or internal to external regions.
Electromagnetic disturbance: Any electromagnetic phenomenon which may degrade the performance of a device, equipment or system.
EM Code: Coding system to indicate the degree of protection provided by an enclosure against the passage of electromagnetic energy.
Immunity level: Maximum level of a given electromagnetic disturbance incident on a particular device, equipment or system for which it remains capable of operating at a required degree of performance.
Point of entry: Physical location on the electromagnetic barrier where electromagnetic energy may enter or exit a topological volume, unless an adequate protective device is provided.
Shielding effectiveness: Ability of an enclosure to attenuate an electromagnetic signal as it enters or exits the enclosure. This is quantified as the ratio of a signal received without the shield, to the signal received with the shield in place. Shielding effectiveness is frequency sensitive and can exhibit sharp changes dependent on enclosure geometry.
IEC-61000-5-7 EMC testing designates the shielding performance of enclosures. The shielding code has two components. The first component is the frequency band and the second is the shielding performance.
Here is the chart for the frequency band:
|Frequency Band||Shielding Designator|
|10 kHz – 100 kHz||A|
|100 kHz – 1MHz||B|
|1 MHz – 30 MHz||C|
|30 MHz – 1 GHz||D|
|1 GHz – 10 GHz||E|
|10 GHz – 40 GHz||F|
Here is the chart for the shielding code designators:
|Shielding Performance dB||Shielding Designator Value|
An example of an EM Code would be EMx66666. This represents the code for an enclosure that was not tested from 10 kHz to 100 kHz, but provided shielding effectiveness of at least 60 dB over the other frequency ranges.
If you are looking for the best IEC 61000-5-7 test lab, look no further than Keystone Compliance. Our experienced engineers are shielding effectiveness experts. We can complete enclosure testing on essentially any size enclosure. Contact us today to experience why so many manufacturers partner with Keystone Compliance to meet their EMC testing needs.