EMI vs EMC – What is the difference?

Electromagnetic Interference (EMI) and Electromagnetic Compatibility (EMC) are two common, but very different topics that we talk about when discussing regulatory testing and compliance of electronic components and systems. In short, EMI refers to the disturbance generated by an external source that affects an electrical circuit through electromagnetic induction, coupling or conduction. It disturbs the normal operation of electronic devices in its sorroundings, causing them to malfunction or produce unwanted behavior. EMC, however, is an electronic device or system's ability to operate without malfunctioning in the presence of electromagnetic interference. Let’s discuss EMI and EMC separately.

Electromagnetic Interference (EMI)

Electromagnetic interference (EMI) refers to the disturbance caused by electromagnetic signals on the operation of electronic devices or systems. These disturbances can manifest as noise, signal degradation, or complete malfunction, leading to operational issues and potentially compromising the functionality of affected equipment. There’re various sources of EMI both natural and man-made. Man-made sources of EMI can be any electronic system through which electric current flows. Natural sources include events like solar flares, lightning, and auroras.

EMI has diverse effects on the performance of electronic systems, It may result in signal degradation causing distortion or loss of transmitted information. In some cases, it may disrupt normal operations to a point where extreme malfunction of complete failure of the device occurs. Therefore, it becomes extremely important to follow the practices which can help to mitigate EMI. This includes shielding sensitive components with metallic enclosures and ensuring proper grounding to protect the electronics inside. Twisted pair cables are also used to cancel out the effects of interference. Additionally, adherence to regulatory standards for electromagnetic compatibility further help in mitigating the effects of EMI.

Electromagnetic compatibility (EMC)

Electromagnetic compatibility (EMC) refers to the ability of electronic devices to function properly in a given electromagnetic environment without causing electromagnetic interference (EMI) to other devices in the vicinity. It ensures that electronic systems can operate without disrupting each other or being disrupted by external electromagnetic signals.

EMC includes both emission of electromagnetic waves and immunity against them. Emission deals with the unintentional generation of electromagnetic energy by a device and its transmission in the environment. These emissions should be kept within acceptable limits to prevent interference with other nearby devices. Immunity is the ability of the device to operate as intended despite being exposed to electromagnetic disturbances from external sources. Electronic devices need to be designed in such a way that they’re immune to such disturbances to maintain their functionality and reliability. This can be achieved by following various strategies like proper design practices, shielding, filtering, grounding, and compliance testing.

In conclusion, Electromagnetic compatibility (EMC) and interference (EMI) are both extremely important design considerations. Failing to consider them in the initial stages of product development can result in the time-consuming and costly need to redesign the product at a later stage to meet EMC/EMI specification tests and prevent product failure or safety risk.