Difference between EMI, EMS and EMC

07 February 2025

The terms EMI, EMS and EMC are often used in the field of communications, but they can be confusing for beginners. What is the difference between these terms?

What is EMI?

EMI stands for electromagnetic interference. It refers to unwanted electromagnetic signals that interfere with the normal operation of electronic equipment. EMI can be caused by natural sources (such as lightning, solar flares) or man-made sources (such as motors, radio transmitters, power lines), which can affect the performance of nearby equipment, causing malfunctions or communication errors. For example, if your cell phone signal drops, or you hear static noise, that's EMI at work.

Types of EMI:

Conducted EMI: Noise is transmitted through physical connections such as wires and cables.

Radiated EMI: Noise is transmitted through electromagnetic waves in the air.

What is EMS?

EMS stands for electromagnetic susceptibility. It refers to the sensitivity of a device to external electromagnetic interference. Devices with high EMS are susceptible to EMI from other devices. If a poorly shielded speaker is placed near a strong radio transmitter, it may generate unwanted noise. EMS ensures that the device can operate normally in an environment with high levels of electromagnetic interference.

What is EMC?

EMC stands for electromagnetic compatibility and is the ability of a device to operate properly in an electromagnetic environment without causing or being affected by EMI. EMC is achieved by shielding, grounding, and filtering techniques.

Conclusion

EMI refers to the interference itself, which can cause problems with a device. EMS describes the degree to which a device is affected by interference. EMC is the overall ability of a device to coexist with other devices in an electromagnetic environment without encountering problems. Think of electronic devices as people in a crowded room, then EMI is like someone shouting loudly and disturbing everyone else, EMS is about people being easily distracted by noise, and EMC is about the overall harmony in the room, where everyone can talk and listen without interruption.

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