Electromagnetic Interference Explained
Electromagnetic interference (EMI) is the distortion resultant on to:
an existing electromagnetic field, or
a conductor, termed a "receptor."
When EMI couples to a person (Yes, we are very conductive.), the correct engineering term for this receptor type is “victim.”
Here you see a current probe reading of an Apple Trackpad. Rather than the sine wave being smooth, it is very jagged. Notice the 645.9 kHz Frequency. A smooth sine wave would be 60 Hz. Copyright © 2020
EMI causes the altering of an electrical waveform and direction of an electron path due to an interaction with a strong intercepting or coupling electromagnetic field that has a different frequency. Interference can occur on any electrical conductor; both electronic and biologic.
With the exponential increase of wireless technologies around the world, EMI has become common vernacular. Synonyms are: signal to noise ratio (SNR), line noise, harmonic transients, dirty electricity, RFI (radio frequency interference), and electromagnetic coupling.
I prefer electrical engineering terms because I communicate with engineers everyday.
The Four Types of Electromagnetic Coupling are:
1. Inductive Coupling occurs when a strong electromagnetic force, or EMF, intersects an electrical conductor within a magnetic field, causing the first magnetic field to become distorted. The famous Michael Faraday, who developed what is now termed the Faraday Cage, discovered electromagnetic induction in 1831. James Clerk Maxwell, who preceded Albert Einstein, mathematically described this process as "Faraday's Law of Induction.".
Because of Faraday's Law of Induction," the Zeeman Effect, 60 Hertz magnetic fields interfere with lower frequencies; the brain (0.5-30 Hz), heart (1-1.7 Hz), nervous system, blood, and everything else biologic.
(Interestingly, The human limbic system (Dr. Jerry Tennant and Dr. Boyd Haley, and now many others) as storing a magnetic field resulting from past emotions. One therapy called "brain reprogramming, retraining, or rewiring" has some claiming success with helping some cope with electro-hypersensitivity (EHS), also termed by me a few years ago as EMF Sensitivity™. The idea is that if you relieve stored emotional strain, then the magnetic field will be mitigated, thus reducing the symptoms. Whether this is all real science or not the result of a placebo effect, is difficult, but as I stated at the onset of this paragraph, it is interesting.)
2. Conductive Coupling occurs when the coupling path between the source and the receptor forms a direct electrical contact with a conducting body,
Examples of Conductive Coupling occur when wires cross in an electronic device, when a human touches an active wire, when a neutral wire is coupled on to an active water pipe which is conducting a neutral current from an opposite direction.
When the signal to noise ratio appears in phase, in the same direction on both conductors, we call this common impedance.
When the signal-to-noise ratio appears out of phase, in the opposite direction on both conductors, we call this differential impedance.
3. Capacitive Coupling occurs when two fluctuating electrical fields co-exist between two adjacent conductors, thereby inducing a change in voltage on the receiving conductor, or receptor. Capacitive Coupling is one of the most intriguing and challenging for the new student to grasp. We see this occurring when we turn off the circuit in a room, and the electric field becomes stronger. It is because the electrician strung to wires in parallel from different circuits.
4. Radiative Coupling occurs when there is a distance exceeding one wavelength between the source point and the receptor. The source point and receptor both act as antennas whereby the source-point emits or radiates an electromagnetic force which then emits across space in between and is coupled or received by the receptor. Radiative Coupling is the most common form of EMI. Examples are:
you are walking past a 5G network Microcell Node (5G antenna.)
the RF from a nearby cellphone transmitter or WiFi router coupling onto unshielded (Romex) electrical wiring in your home or office
using your cellphone to your ear (This combines all four of the types of coupling!)
Why Be Concerned About EMI?
Electromagnetic interference (EMI) causes latency, malfunction, and sluggish performance to fine electronics such as computers, medical devices and equipment, pace-makers, financial trading platforms, graphic software, recording equipment, and more.
How Do You Know It’s EMI?
An easy way to tell if you have an EMI issue is to observe the presence of any:
overheating of any metal enclosures. Are enclosures very hot to the touch? (Inductive Heating)
motor failures from overheating. (Voltage Drop)
fuses blowing for no apparent reason (Inductive Heating and Overload)
static or interference on sound or voice communication (Harmonic Line Noise)
electronic equipment shutting down for no apparent reason (Voltage Distortion)
computer malfunction or locking up. (Voltage Distortion)
flickering fluorescent or LED lights (Transformer Saturation)
blinking incandescent lights (Transformer Saturation)
flickering or distortion lines and static on screens (Transformer Saturation)
What Are the Additional Benefits of Reducing EMI?
Reduced Electrical Consumption
Cooler Equipment
Longer Lifetime for Equipment
Lowered Utility Bill
EMF Reduction for a Safer and Healthier Environment
Surge Protection for Your Entire Facility
Improved Screen Quality
Improved Audio
Phase Correction Which Improves Efficiency and Performance
Cleaner Power Resulting from Transient Harmonic Attenuation
Improved Health and Wellness
How Does EMI Occur?
Metal, of course, is a conductor for electromagnetism. If you have a strong electromagnetic field nearby a metal wire that has an electrical current and/or voltage, the nearby electromagnetic field will magnetically converge, couple, and ride along with the original current. Imagine a surfer hopping onto his surfboard to ride that perfect wave.