Compliance Engineering Reference Guide
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If an EMC engineering expert re-designed the hair dryer so that it wouldn't produce
electromagnetic interference, the annoying lines would go away.
The hair dryer and the television set would then be compatible with each other.
They would have acheived "Electromagnetic Compatibility" (EMC.)
EMI and EMC engineering are used interchangeably to refer to the technology
of preventing and eliminating electromagnetic interference.
Other names for this technology include "Radio Frequency Interference "
(RFI) and "Radio Interference."
Amateur radio operators call it " QRM " and " QRN ."
"Emissions" and "Susceptibility" are two important concepts in the field of electromagnetic compatibility.
The radio signals that the hair dryer produces are its "emissions."
The extent to which the television set malfunctions in the presence of these signals
is called its "Susceptibility."
Electromagnetic Compatibility can be acheived by either of the following EMC engineering techniques:
Many Electromagnetic Compatibility ( EMC ) engineering specifications require tests for both
the EMISSIONS that a device produces, and for
its SUSCEPTIBILITY to the emissions produced by other devices.
In Europe, "Susceptibility" tests are called "Immunity" tests.
The field of electromagnetic compatibility ( EMC ) engineering encompasses several
sub-specialties. Some of these are:
* Electrostatic Discharge Control (ESD), the prevention of damage
caused by static electricity, like the kind that you produce by walking
across a carpet on a dry day. These little shocks may not seem like much,
but electronic circuits, as they are made smaller and smaller, become
increasingly SUSCEPTIBLE
to being damaged by these little shocks.
Even shocks that are too small to feel can cause damage.
* Radiation Hazards (RADHAZ), protection against injuries that can be
caused by powerful radio transmitters.
*High Energy Radio Frequency (HERF) protection: Protection against
electromagnetic interference that is intentionally caused by
mischief-makers.
When you fill your car's gasoline tank, you may see a sign warning you
to turn off your cell phone.
This is because radio signals, like the ones produced by cell phones,
have been known to cause sparks that can
ignite gasoline fumes and cause a fire.
The term "HERF" is also used to mean "Hazards of Electromagnetic
Radiation to Fuel."
*Extremely Low Frequency ( ELF) signals, such as those produced by electrical power lines, have been accused of causing electromagnetic interference and even health problems. The study of ELF signals and their effects is also a part of the overall field of electromagnetic compatibility.
* Electromagnetically Shielded Enclosures are used in EMC engineering to
block unwanted radio signals from getting in or out. This general term is used to
refer to enclosures that can be several stories tall,
or small enough to fit on a printed circuit board.
* Shielded Enclosures that are approximately the size of a typical room or office
are often called " shielded rooms, " or (in Canada) "Walk-in shielded enclosures"
or "Faraday Cages " after the British scientist
Michael Faraday
who invented the first one,
Shielded rooms were originally made of copper screening fabric.
They were called "Screen Rooms," and the term is still used today.
* Shielding Effectiveness Testing is the technology used to determine if a
sheilded enclosure is working properly. It is also used in EMC engineering to determine the
effectiveness of different types of shielding materials.
For more information about shielding, see:
"THE SHIELDED ENCLOSURE HANDBOOK"
and these COURSES.
entitled:
SHIELDING EFFECTIVENESS TESTING
CONSTRUCTION OF ELECTROMAGNETICALLY SHIELDED ENCLOSURES
* "TEMPEST" is a sub-specialty of electromagnetic compatibility ( EMC ) enginering.
It deals with the prevention of electronic eavesdropping.
Most information about TEMPEST engineering is classified.
People who work in this field
are prohibited by the U.S. Government
from discussing it with anyone who does not have
a security clearance and a need to know
the information.
To learn more about Electromagnetic Compatibility ( EMC ) engineering,
see this one-day course:
Introduction to Electromagnetic Compatibility"
Copyright 1998 - 2010 by The Herndon Company. All rights reserved.
site map
Absorbing Material - RF:
Amplifiers: for electromagnetic compatibility testing.
Anechoic Chambers: see shielded enclosures.
Antennas and TEM Cells:
BOOKS:
Cable, Coaxial:
Cable, Shielded: see "Shielded Cable"
CE Mark Test Equipment: see "Test Equipment"
Chokes: see "Inductors"
Crystal oscillators:
Courses:
Current Probes:
d.c to d.c. converters:
Electric Field Monitors:
Electrostatic Discharge (ESD) Protection Devices
Electromagnetic Pulse (EMP) Protection Devices
European Community - special electromagnetic compatibility test equipment: see "Test Equipment"
Ferrites: Beads, Toroids, etc.
Fiber Optic Devices for EMC Design and Testing.
Filters: for a.c. power lines:
Filters: for d.c. power lines:
Filters: for signal lines:(see also "Ferrites")
High Energy Radio Frequency (HERF) Protection: See Electromagnetic Pulse
High Intensity Radio Frequency (HIRF) Protection: See Electromagnetic Pulse
Inductors
Instruments: See Test Equipment
Lightning: see "Electromagnetic Pulse"
Line Impedance Stabilization Networks (LISN's):
Manufacturers representatives:
Magnetic Shielding Materials:
Magnetic Field Cancellation:
Open Area Test Sites (OATS):
Microwave Absorbing Material:see Absorbing Material
Power Supplies:
Radiation Hazard Meters:
SCIFs: see shielded enclosures.
Sensitive Compartmented Information Facilities: see shielded enclosures.
Shielded Backshells
Shielded Bags:
Shielded Cable
Shielded Enclosures:
Shielded Glass.
Shielded Pouches:
Shielded Switching Units:
Shielded Rooms:
Shielded Tents:
Shielding Effectiveness Testing:
Shielded Enclosure Testing: See "Shielding Effectiveness Testing"
Shielded Vents:
Shielded Windows.
Shielding Materials:(see also Magnetic Shielding Materials)
Software:
Spread Spectrum Timing Devices:
Surge Protection: see "Electromagnetic Pulse"
TEM Cells: see "Antennas"
TEMPEST Switches
Test Equipment: general:
Test Equipment for European Community electromagnetic compatibility testing:
Test Equipment Rental:
Training: see "courses"
Vents: see "shielded vents"
If you cannot find what you need in our EMC engineering directory, try these:
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The data contained herein is for information purposes.
While every attempt was made to check the accuracy of the material
contained herein, there may be errors beyond our control.
Reference, in these web pages, to any specific products, services,
companies, or manufacturers
does not constitute their endorsement or recommendation by
TEMPEST INC. or THE HERNDON COMPANY. Neither TEMPEST INC. nor
THE HERNDON COMPANY are responsible for,
nor do they necessarily endorse,
the contents of any 'off-site' web pages referenced from
this web site.
(a) Reducing the EMISSIONS of the hair dryer, or:
(b) Reducing the SUSCEPTIBILITY of the television set.