For electronic devices to function normally, electromagnetic interference (EMI) or noise must be mitigated at all costs, and there are various solutions, such as shielding and coating, that manufacturers adopt to achieve the same. Over the last few years, much emphasis has been placed on making electromagnetic compatible devices. What is electromagnetic compatibility and how is it different from interference? Electromagnetic interference and electromagnetic compatibility may seem similar, but they are two different terms and concepts. While electromagnetic interference (EMI) is produced by the clashing of signals produced by certain devices, board components, and so on, electromagnetic compatibility (EMC) is the ability of electronic devices to function normally in the presence of EMI. This means a device must be electromagnetically compatible to avoid any damage due to EMI. Since these concepts are different, their testing methods and tools are also different. This post discusses the differentiating factors between electromagnetic interference and compatibility testing.
Objectives of Electromagnetic Interference Testing and Electromagnetic Compatibility Testing
EMI and EMC must be considered during the design stage to ensure achieving the objectives. The purpose or aim of EMI testing is different from that of EMC testing. EMC testing is more focused on checking if the device can function in the presence of EMI within acceptable levels or as mentioned by the manufacturer. On the other hand, EMI testing focuses on the electromagnetic signals emitted by a device and if they can interfere with signals from other connected devices, mounted components on a printed circuit board (PCB), cables in the vicinity, and more. Here are some differentiating pointers on the purpose of EMI and EMC testing.
- Electromagnetic interference testing is done to identify and quantify the unintentional emissions from a device.
- This testing also checks if the emissions are within acceptable limits set by regulatory standards to prevent interference with other devices.
- Electromagnetic Compatibility Testing is done to validate if the device can function correctly when exposed to electromagnetic disturbances.
- It also helps ensure that the device does not emit electromagnetic radiation which may interfere with other devices.
Tests Performed for EMI and EMC Measurements
The EMC testing covers conducted and radiated interference, because EMI can affect power supplies through conduction and radiation. The following are common types of electromagnetic compatibility and electromagnetic interference testing performed on power lines.
- Emission Tests: These tests analyze the EMI generated by the tested device. Engineers analyze antennas, spectrum analyzers, or antennas to check the electromagnetic noise generated by them.
- Conducted Emissions Test: The testing measures the internal electromagnetic energy generated that may travel to long distances along the cable and cause interference on other systems.
- Radiated Emissions Test: This test is performed to measure the electromagnetic noise emitted through the air to check the extent to which it can affect the device’s testing.
- Immunity Tests: This testing is performed to determine a product’s susceptibility to EMI. It helps evaluate how a product reacts to intermittent and continuous exposure to electromagnetic energy. The tested device is subjected to various frequencies to check their response to electromagnetic noise and its impact on power supply. Two types of immunity tests are performed:
- Conducted Immunity Tests: This testing measures how the tested device reacts to the electromagnetic energy produced in another source and carried to it by a cable.
- Radiated Immunity Tests: This testing measures how the tested device performs on exposure to electromagnetic energy in its regular operating environment.
Just like electronic devices, board-level EMI must also be curtailed. While testing of EMI and EMC is crucial, considering these aspects at the design level is just as important even at board level. This can be achieved through effective PCB EMI shielding, comprising a combination of grounding techniques, use of thin and lightweight EMI shields, and more. While most devices now are designed to be EMC compatible, EMI shielding helps control board level internal and external noise. Plasticized EMI shields prevent unwanted signals and subsequent damage to the board and in turn, the system of the device. XGR Technologies offers SnapShot® EMI shields made from a thin polyetherimide film on the interior and conductive tin on the exterior surfaces. These flexible and lightweight shields can be easily used on any type of PCB to mitigate electromagnetic inference across applications. If you need further information on SnapShotTM EMI shields and their effectiveness in shielding EMI in PCBs, you can contact the team at XGR Technologies via phone or email.
