What is electromagnetic compatibility testing? Why EMC testing is required? How EMC testing is done?

1. Electromagnetic compatibility testing
Asif Khan
Faculty Elect. Department,
Rustomjee Acedamy for Global Careeres, Dahanu
asif@ragc.in
Abstract- We are surrounded by many types of electromagnetic waves such as radio signals and other frequencies. The
electronic equipments are designed to work on a particular frequency, they can malfunction due to any interference of
external signal or even this equipment can emit unwanted signal due to which problems can arise with other systems or
equipments, to ensure that this does not happen government has made some guideline known as Electromagnetic
compatibility directives. This technical paper presents the simplified explanation of Electromagnetic compatibility with
examples of few tests conducted on products to achieve compliance with EMC directives. It further tries to explain how
simple steps can be taken while designing an electronic circuit to improve EMC performance of the circuit.
Keyword - electromagnetic wave, radio signal, interference, directives compatibility, compliance
INTRODUCTION
The purpose of an electromagnetic compatibility test is to
ensure that an electrical or electronic device/ product
does not emit radio-active signals that can affect the
functionality of any other device near it and at the same
time the functionality of any electrical/ electronic device
or product should not be affected by the emission of
radioactive signal from the product/ device manufactured
by a company. There are various legislations and
standards in place for product manufacturing companies
to ensure the compliance such as ARE 47000-6-3 (2002)
electromagnetic compatibility standard in India, EMC
directive (2014/30/EU) etc.
Why EMC testing is important?
1. There is a limited range of electromagnetic
spectrum that can be used today as there fixed
frequency bands used radio transmission,
microwave communication X ray machines
military applications etc. If an electronic
product emits unwanted radiation it will
adversely affect the frequency band reserved for
other devices.
2. In many product EMC performance becomes
extremely critically as it poses a threat for our
safety, such as a CT scan machine has a huge
magnet that can attract a 500 Kg weight car if its
within the range of its magnetic field a
considerably Medical equipment directives
provide instruction to keep electromagnetic
signal emission to an acceptable level.
3. F the power regulation of an internal power
supply can cause error in measuring devices
used in the lab; an externally applied radiation
can corrupt the data of critical device.
4. EMC testing is a requirement by Law and if a
manufacturer is found not carrying out an EMC
test as required he may be fined if his product is
to be sold in European market or his license can
be canceled or he may be put behind the bars.
Common test methods for Electromagnetic
compatibility
Radiated emission test:
Pre-compliance test chamber is a metal box where the test
is conducted; metal walls ensure that there is no external
signal to get into the chamber as the test is being
conducted. This test is done in anechoic (Non reflective)
or semi anechoic chamber which means that the wall of
the test chamber consists of a material that does not
reflect any radiation emitted from the test device which
prevent antenna catching any wrong signal or ensures
accurate result. As per the standard Device under test
should be placed on the wooden table and the emissions
are caught up by the antenna and emitted radiations are
compared against the limit lines defined in the EMC
directive. To get the best result device under test is a
rotated at a fixed speed and the antenna is kept in
horizontal position to capture maximum emitted signal
through the device.
Equipments required:
1) Anechoic (Non reflective) or semi anechoic
chamber
2) SpectrumAnalyzer:
3) Antenna
Conducted Emission:
EMC directive requires the amount of radio frequency
signal on any cable connected to a device should not
exceed a certain limit specified by directive.
Immunity test: Common immunity tests
Electro static discharge test

2. 2
A vertical coupling plan- horizontal coupling plane, a
wire attached to a metal plane on the floor through a one
mega Ohm resistor. The devices under test are kept on a
table between vertical and horizontal coupling planes. An
EST discharge test device is used which has two types of
signals one is conducted discharge and the other one is air
is air discharge tube. EST discharge device discharges a
signal on vertical plane then on the horizontal plane and
on the housing of the device under test. Then an air
discharge is done on one of the screws of the housing of
the device. If the equipment under test operates without
any disruption that means product has passed the test.
Common test methods for Electromagnetic
compatibility
Radiated emission test:
Pre-compliance test chamber is a metal box where the test
is conducted; metal walls ensure that there is no external
signal to get into the chamber as the test is being
conducted. This test is done in anechoic (Non reflective)
or semi anechoic chamber which means that the wall of
the test chamber consists of a material that does not
reflect any radiation emitted from the test device which
prevent antenna catching any wrong signal or ensures
accurate result. As per the standard Device under test
should be placed on the wooden table and the emissions
are caught up by the antenna and emitted radiations are
compared against the limit lines defined in the EMC
directive. To get the best result device under test is a
rotated at a fixed speed and the antenna is kept in
horizontal position to capture maximum emitted signal
through the device.
Equipments required:
1) Anechoic (Non reflective) or semi anechoic
chamber
2) Spectrum Analyzer:
3) Antenna
Conducted Emission:
EMC directive requires the amount of radio frequency
signal on any cable connected to a device should not
exceed a certain limit specified by directive.
Immunity test: Common immunity tests
Electro static discharge test
A vertical coupling plan- horizontal coupling plane, a
wire attached to a metal plane on the floor through a one
mega Ohm resistor. The devices under test are kept on a
table between vertical and horizontal coupling planes. An
EST discharge test device is used which has two types of
signals one is conducted discharge and the other one is air
is air discharge tube. EST discharge device discharges a
signal on vertical plane then on the horizontal plane and
on the housing of the device under test. Then an air
discharge is done on one of the screws of the housing of
the device. If the equipment under test operates without
any disruption that means product has passed the test.
REFERENCES
(2016). Getting EMC Design rights first time. In P. R.
Alan Herr, Get EMC right first time. SimplyEmc.com.
Learn EMC . (2016). Retrieved from EMC Fast Pass:
http://www.emcfastpass.com/emc-testing-beginners-
guide/emissions/
Poole, I. (n.d.). Radio electronics.com. Retrieved from
http://www.radio-electronics.com/info/circuits/emc-
emi/electromagnetic-interference-basics-tutorial.php
BIOGRAPHY
Asif Khan completed Diploma in
Electrical Engineering from Saboo
Siddik Poly technique Mumbai. His
research areas include synchronous
digital hierarchy in Telecom
Industry. He has 6 years of practical
work experience working in telecom
and electrical facility management
companies
At present he is working with
Rustomjee Academy for Global
Careers as Faculty in Electrical
Department.