EMC Service | EMC Tech

Electromagnetic Interference – Its Meaning and the Way It Affects Us

Electromagnetic Interference – Its Meaning and the Way It Affects Us

EMI is the recognised acronym for electromagnetic interference. It is a function of electromagnetic energy that affects electronic equipment and devices.

The science of EMI relates to the concepts of EMC (electromagnetic compatibility) and EMR (electromagnetic radiation).

Com-Power Corporation explains EMI in the following terms:

“EMI can be defined as electromagnetic energy which affects the functioning of electronic devices. EMI is also called radio frequency interference (RFI) where it is a disturbance caused by electromagnetic induction, electrostatic coupling, or conduction.”


Electromagnetic Interference | EMC Tech


What sources cause EMI?

The sources that produce EMI can be natural, or other electronic devices.

Natural sources. These include electrical storms, lightning in particular, solar magnetic storms, atmospheric noise, and the earth’s magnetic field.

Equipment sources. Typical sources that generate EMI include equipment types like welders, electric motors, electrical contacts, TV and wireless transmissions, LED screens, and integrated circuits.

Industrial systems. Electric utility transmission lines, broadband digital signals, airport radar equipment, railroad and mass transit systems.

Medical systems. EMI sources include ventilators, electric wheelchairs, MRI systems, X-ray units, telemetry and electrocardiogram units.

Power degradation. Effects include voltage surges, dips, blowouts and blackouts, power line faults, and superimposed electrical noise.


The effects of EMI

The benign effects of EMI  affect the operation of computers, mobile phones, home entertainment systems, vehicle sound systems, cordless phones, wearable technology gadgets, and many more commercial devices.

More critical effects of EMI include its potential effects on mission-critical systems, some of which may cause life-threatening risks. Such effects include:

  • Avionics systems like the electronic guidance systems that control aircraft landing approaches.
  • Military equipment, ordnance, and electronically controlled weapon systems.
  • Industrial or commercial electronic systems that control automatic processes.

There is also a growing body of science that claims EMI effects on human health. Research claims the human body is “bio-electronic” and utilises many electromagnetic processes to control the way our brain, nervous and immune systems function. More information on this can be found in an article published by Michael R. Neurt titled “Do EMFs Really Affect Our Health?


Destructive uses of EMI

In military and terrorist circles, there is something called HEMP (High Powered Electromagnetic Pulse) devices designed to disrupt or disable electronic systems.

There are half a dozen of specially designed HEMP weapons intended for warfare. They range from nuclear, microwave, E-bombs, and cannons. All of them utilise electromagnetic energy.


EMI by source category

These sources are based on scientific or engineering classifications and may have limited value to casual observers of EMI.

There are two types of EMI. There is conducted EMI where there is physical contact between source and victim, and radiated EMI caused by induction.


Further classifications include:


Continuous interference and Impulse noise. Continuous background noise may be man-made or natural. Natural sources include lightning and ESD (static energy).

If man-made, it would come from an electronic circuit that is emitting continuous energy, or from switching systems.

Narrowband noise. Single carrier source like an oscillator, spurious noise from a transmitter, mobile phone, or Wi-Fi router.

Broadband signals. Caused by heavy man-made equipment like arc welders, or natural noise from the sun.

Coupling mechanisms. The source emits a signal and the victim suffers disruption to its performance on the receiving end. Conducted coupling happens when there is a route along which the signal can travel. This may be power or interconnection cables.