Natural sources of “Electromagnetic Field (EMF)” or “Electric and Magnetic Fields” are present everywhere in our environment. Electric fields are produced by the build-up of electric charges associated with thunderstorms. The earth’s static DC magnetic field is present everywhere on the planet and far out into space. Man-made EMF sources are ubiquitous in any developed society: subway rail systems and medical MRI equipment produce strong DC fields; passing electric distribution lines and building electrical equipment emit AC magnetic fields; broadcasting, cellular and other communication transmitters and radar systems generate powerful RF electromagnetic fields.
Electromagnetic interference (EMI) is unwanted noise or interference in an electrical path or circuit caused by an outside source. EMI can cause electronics to operate poorly, malfunction or stop working completely.
EMI can be caused by natural or human-made sources. Using high quality electronics, electrical shielding, and modern error correction can reduce the impact of EMI.
A common example of EMI is when a cellphone is placed near powered audio equipment or speakers, and it causes a noise or series of beeps to be heard.
EMI occurs because of the close relationship between electricity and magnetism. All electrical flow produces a small magnetic field. Conversely, a moving magnetic field produces an electrical current. These principals allow electric motors and generators to work. Additionally, all electrical conductors can operate as radio antennas. High powered electrical and radio sources can produce unwanted effects in devices far away. As electronics become smaller, faster, more tightly packed and more sensitive, they become more susceptible to these effects, causing EMI.
In EMI there is a source, a path and a receptor (or victim). There are several types of paths, or methods of transmission of EMI from the source to the receptor.
"Conducted EMI" happens when there is a physical electrical path from the source to the receptor. This is often along power transmission lines. Some sources may be a large motor or power supply. An example of conducted EMI is the turning on of a treadmill or clothes dryer causing a computer on the same electrical mains circuit to reboot.
There are two categories of Conducted EMI.
1.Common Mode EMI – A high-frequency EMI that flows in the same direction through one or more conductors.
2.Differential Mode EMI – A low-frequency EMI that flows in an opposite direction though adjacent wires.
Radiated EMI – The most common type of EMI, caused by radiating electromagnetic fields. Common manifestations of radiated EMI include static noise on AM/FM radio receivers and “snow” on TV monitors.
"Coupled EMI" happens when the source and receptor are close together, but not electrically connected. Coupled EMI can be transmitted through induction or capacitance.
'Inducted or magnetically coupled EMI' happens when a conductor’s magnetic field induces an unwanted current in a nearby conductor. An example of inducted EMI is when a power cable and an audio cable are near each other, and a hum is heard on the audio line.
'Capacitively coupled EMI' happens when two conductors are parallel and store a capacitive charge between them. Capacitively coupled EMI requires the conductors to be very close together and is most common on electronic circuit boards or in groups of closely packed wires running long distances.
"Radiated EMI" happens when a high-power transmitter or electrical device produces a radio frequency that is picked up and causes unwanted effects in another device. Radiated EMI can be subdivided into narrowband and broadband interference. Narrowband EMI only affects a specific radio frequency and is commonly from a radio transmitter. Broadband EMI affects a large portion of the radio spectrum at many frequencies and is commonly caused by malfunctioning equipment.
Electromagnetic compatibility (EMC) of an electrical, electronic, or RF device has two facets:
The ability to work properly in the presence of electromagnetic radiation. The ability to not generate, propagate unintentional EMI that affects the operation of other devices in its vicinity.
The goal of EMC is the correct operation of different equipment in a common electromagnetic environment. While EMI is the problem, EMC counteracts to control EMI.
EMI/EMC testing for any electrical and electronic products as per International Standards such as EN/IEC/UL/SAE etc., and National Standards IS/BS/VCCI/CSA/FCC etc., could be supported by us.
