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Making EMI
Compliance Measurements
Application Note
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Table of Contents
Introduction to compliance measurements...................................................................... 3
The compliance measurements process .......................................................................... 4
Compliance EMI receiver requirements ............................................................................ 7
Requirements above 1 GHz ...................................................................................... 8
Conducted emissions measurements................................................................................ 9
Conducted test setup ................................................................................................ 9
Configuring the receiver............................................................................................ 9
Performing conducted emissions measurements............................................ 11
Radiated emissions measurements..................................................................................13
Open site requirements...........................................................................................13
Radiated emissions test setup ..............................................................................14
Measuring radiated emissions ..............................................................................15
Placement of EUT for maximum signals .........................................................................16
Ambient plus EUT measurements........................................................................16
Appendix A - Line impedance stabilization networks..................................................17
Appendix B - Antenna factors............................................................................................19
Appendix C - Basic electrical relationships ....................................................................21
Appendix D - Detectors used in EMI measurements ...................................................22
Appendix E - EMC regulatory agencies ...........................................................................25
Glossary of acronyms and definitions..............................................................................26
2
Introduction to compliance
measurements
Electrical or electronic equipment that uses the public power grid or has
potential for electromagnetic emissions must pass EMC (electromagnetic
compatibility) requirements. These requirements fall into four broad
types of testing: radiated and conducted emissions testing, and radiated and
conducted immunity testing.
Conducted emissions testing focuses on signals present on the AC mains that
are generated by the equipment under test (EUT). The frequency range of these
measurements is typically 9 kHz to 30 MHz. However, MIL-STD measurement
may have a wider frequency range.
Radiated emissions testing searches for signals being emitted from the EUT
through space. The typical frequency range for these measurements is 30 MHz
to 1 GHz or 6 GHz, although FCC regulations require testing up to 40 GHz.
Figure 1 illustrates the difference between radiated emissions, radiated
immunity, conducted emissions, and conducted immunity. Radiated immunity
is the ability of a device or product to withstand radiated electromagnetic fields.
Conducted immunity is the ability of a device or product to withstand electrical
disturbances on power or data lines. Immunity testing will not be covered in
this document.
For an electromagnetic compatibility problem to occur (such as when an
electric drill interferes with TV reception), there must be a generator or
source, a coupling path, and a receptor. Until recently, most efforts to remove
EMC problems have focused on reducing the emissions of the source to an
acceptable level—now both emissions and immunity tests are performed.
Emission
Immunity = Susceptibility
Figure 1. Four types of EMC measurements
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The compliance
measurements process
Before compliance measurements can be performed on a product, some
preliminary questions must be answered:
1. Where will the product be sold (for example, the United States,
Europe, or Japan)?
2. What is the classification of the product (for example, information
technology equipment (ITE); industrial, scientific, or medical (ISM);
or automotive and communications)?
3. Where will the product be used (for example, home, commercial, light
industry, or heavy industry)?
With the answers to the above questions, you can determine which testing
requirements apply to your product by referring to Tables 1a and 1b below. For
example, if you have determined that your product is an ITE device that will
be sold in the U.S., then you need to test the product to FCC Part 15 regulations.
International regulations summary (emissions)
CISPR
FCC
EN
Description
11
Part 18
EN 55011
Industrial, scientific, and medical
13
Part 15
EN 55013
Broadcast receivers
14
EN 55014
Household appliances/tools
15
EN 55015
Fluorescent lights/luminaries
16-1-1
Measurement apparatus/methods
22
Part 15
EN 55022
Information technology equipment
25
EN 55025
Automotive
EN 50081-1,2
Generic emissions standards
Table 1a. Comparison of regulatory agency requirements
European Norms (EN)
Equipment type
Emissions
Generic equipment
EN 50081-1
Residential
Light industrial
Industrial
EN 50081-2
Industrial, scientific, medical products (ISM)
EN 55011
Sound and broadcast receivers
EN 55013
Household appliances
EN 55014
Information technology equipment (ITE)
EN 55022
Automotive
EN55025
Table 1b. Major European requirements
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European Norms
EN55011 (CISPR 11)
Industrial, scientific, and medical products
Class A: Used in establishments other than domestic areas.
Class B: Suitable for use in domestic establishments.
Group 1: Laboratory, medical, and scientific equipment. (For example, signal
generators, measuring receivers, frequency counters, spectrum analyzers,
switching mode power supplies, weighing machines, and electronic
microscopes.)
Group 2: Industrial induction heating equipment, dielectric heating equipment,
industrial microwave heating equipment, domestic microwave ovens, medical
apparatus, spark erosion equipment, and spot welders. (For example, metal
melting, billet heating, component heating, soldering and brazing, wood gluing,
plastic welding, food processing, food thawing, paper drying, and microwave
therapy equipment.)
EN55014 (CISPR 14)
Electric motor-operated and thermal appliances for household and similar
purposes, electric tools, and electric apparatus. Depending on the power rating
of the item being tested, use one of the limits shown in Table 1c.
EN55014 Conducted household appliances QP
EN55014 Conducted household appliances AVE
EN55014 Conducted < 700 W motors QP
EN55014 Conducted < 700 W motors AVE
EN55014 Conducted > 700 W < 1000 W motors QP
EN55014 Conducted > 700 W < 1000 W motors AVE
EN55014 Conducted > 1000 W motors QP
EN55014 Conducted > 1000 W motors AVE
EN55014 Radiated household appliances QP
EN55014 Radiated household appliances AVE
EN55014 Radiated < 700 W motors QP
EN55014 Radiated < 700 W motors AVE
EN55014 Radiated > 700 W < 1000 W motors QP
EN55014 Radiated > 700 W < 1000 W motors AVE
EN55014 Radiated > 1000 W motors QP
EN55014 Radiated > 1000 W motors AVE
Note: The conducted range is 150 kHz to 30 MHz and the radiated range is 30 MHz to 300 MHz.
Table 1c. Tests based on power rating
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