Electromagnetic compatibility ( EMC ) is a branch of electrical engineering related to accidental generation, propagation and acceptance of electromagnetic energy that can cause undesirable effects such as electromagnetic interference (EMI) or even physical damage to the operational equipment. The purpose of EMC is the correct operation of different equipment in a general electromagnetic environment.
EMC pursues three major classes of problems. Emissions are the generation of electromagnetic energy, whether intentional or unintentional, by some sources and their release to the environment. EMC studies undesirable emissions and possible counter measures to reduce undesirable emissions. The second class, vulnerability , is the propensity of electrical equipment, called a victim, damaged or damaged in the presence of unwanted emissions, known as radio frequency interference (RFI). Immunity is the opposite of vulnerability, because the equipment's capabilities function correctly in the presence of RFI, with the discipline of "hardening" equipment known as vulnerability or immunity. The third class under study is coupling , which is the mechanism by which the transmitted interference reaches the victim.
Interference mitigation and electromagnetic compatibility can be achieved by addressing any or all of these problems, ie, calming sources of interference, blocking couplings and/or hardening potential victims. In practice, many engineering techniques used, such as grounding and shielding, apply to all three problems.
Video Electromagnetic compatibility
Introduction
While electromagnetic interference (EMI) is a phenomenon - emitted radiation and its effects - electromagnetic compatibility (EMC) is the equipment characteristic or property - does not behave acceptable in EMI environment.
EMC ensures correct operation, in the same electromagnetic environment, of different equipment items that use or respond to electromagnetic phenomena, and avoid interference effects. Another way to say this is that EMC is EMI control so unwanted effects are prevented.
In addition to understanding the phenomenon itself, the EMC also addresses countermeasures, such as control regimes, design and measurement, to be taken to prevent emissions from causing adverse effects.
Maps Electromagnetic compatibility
Type of interruption
Electromagnetic interference divides into several categories according to the source and signal characteristics.
The origin of the disorder, often called "noise" in this context, can be man-made (artificial) or natural.
Continuous interference
Continuous, or continuous wave (CW), a disruption arises where the source continually radiates over a certain frequency range. This type is naturally divided into sub-categories according to the frequency range, and as a whole is sometimes referred to as "DC to daylight".
- Audio frequency, from very low frequency to about 20 kHz. Frequencies of up to 100 kHz are sometimes classified as audio. Resources include:
- Main parent of: power supply units, nearby power supply cables, transmission lines, and substations.
- Audio processing equipment, such as audio power amplifiers and speakers.
- Demodulate high frequency carrier waves such as FM radio transmissions.
- Radio frequency interference (RFI), from typically 20 kHz to an ever-increasing upper limit as technology pushes it higher. Resources include:
- Radio and wireless frequency transmission
- Television and radio receiver
- Industrial, scientific and medical equipment (ISM)
- Digital processing circuit such as microcontroller
- Broadband noise can be scattered in parts of one or both frequency ranges, with no particular frequency being emphasized. Resources include:
- Sun activity
- Continuous spark gap like a bow welder
- CDMA (spread-spectrum) mobile phone
Pulse or temporary interruption
An electromagnetic pulse (EMP), sometimes called a temporary disturbance, arises where the source emits a short-energy pulse. Energy is usually broadband by nature, although it often excites a relatively narrow damped sine wave response in victims.
The sources are widely divided into isolated and repetitive events.
- The isolated sources of EMP events include:
- Switch the action of electrical circuits, including inductive loads such as relays, solenoids, or electric motors.
- Electrostatic discharge (ESD), as a result of two closely related objects or contacts.
- Lightning electromagnetic pulses (LEMP), although usually a series of short pulses.
- Nuclear electromagnetic pulse (NEMP), as a result of nuclear explosion. The variant of this is the high level EMP (HEMP) nuclear device, designed to create pulses as the main destructive effect.
- Non-nuclear electromagnetic weapons (NNEMP).
- Power/pulse spike spike
- Recurring sources of EMP events, sometimes as ordinary toll train , include:
- Electric motor
- Electrical ignition system, like on gasoline engine.
- Continuous switch action from digital electronic circuits.
Coupling mechanism
Some technical words used can be used with different meanings. These terms are used here in a widely accepted way, consistent with other articles in the encyclopaedia.
The basic arrangement of noise sources, couplings and victims, receptors or sinks is shown in the figure below. Resources and victims are usually electronic hardware devices, although the source may be natural phenomena such as lightning strikes, static electricity release (ESD) or, in one famous case, the Big Bang in the Universe's origin.
There are four basic coupling mechanisms: conductive, capacitive, magnetic or inductive, and radiative. Any coupling path can be split into one or more of these coupling mechanisms that work together. For example the bottom path in the diagram involves an inductive, conductive and capacitive mode.
Conductive coupling
Conductive coupling occurs when the coupling path between the source and the receptor is formed by direct electrical contact with the conducting body, eg transmission line, wire, cable, PCB trace or metal enclosure.
The noise performed is also marked by the way it appears on different conductors:
- Common-mode combined or common-impedance : noise appears gradually (in the same direction) on two conductors. coupling
- Differential-mode : noise appears outside phase (in opposite direction) on two conductors.
Inductive inductions
Inductive clutch occurs where source and receiver are separated by short distances (usually less than wavelength). Strictly speaking, "Inductive coupling" can consist of two types, electrical induction and magnetic induction. It is common to refer to electrical induction as capacitive coupling , and for magnetic induction as inductive coupling .
Capacitive coupling
Capacitive coupling occurs when an electric field varies between two adjacent conductors usually less than a separate wavelength, causing a change in voltage across the receiving conductor.
Magnetic coupling
Inductive clutch or magnetic coupling (MC) occurs when a varying magnetic field exists between two parallel conductors that are usually less than the wavelength, causing a change of voltage along the receiving conductor.
Radiation hook
The radiative clutch or electromagnetic clutch occurs when the source and the victim are separated by large distances, usually more than one wavelength. Sources and victims act as radio antennas: sources emit or emit electromagnetic waves that spread across the space in between and picked up or received by the victim.
EMC Control
The damaging effects of electromagnetic interference pose unacceptable risks in many areas of technology, and it is necessary to control such interference and reduce the risk to an acceptable level.
Electromagnetic interference control (EMI) and EMC guarantees comprise a series of related disciplines:
- Characterize the threat.
- Set standards for emission and vulnerability levels.
- Design for standard compliance.
- Test standard compliance.
For complex or new equipment, this may require the production of a EMC control plan that summarizes the above implementation and specifies the necessary additional documents. Characterize the threat
Characterization of the problem requires an understanding of:
- Source and interference signals.
- Coupling for victims.
- The nature of the victim either electrically or in the sense of significance of damage.
Risks posed by threats are usually statistical, so much of the work in threat characterization and standard setting is based on reducing the annoying EMI probability to an acceptable level, rather than a convincing removal.
Legal and regulatory
Agency rules and standards
Several organizations, both national and international, are working to promote international cooperation in standardization (alignment), including the publication of various EMC standards. Where possible, standards developed by one organization can be adopted with little or no change by others. This helps for example to harmonize national standards across Europe.
International standards organizations include:
- The International Electrotechnical Commission ( IEC ), which has several committees working full-time on EMC issues. This is:
- The Technical Committee 77 ( TC77 ), works on electromagnetic compatibility between equipment including networks.
- ComitÃÆ' © International Spà © cial des Perturbations RadioÃÆ' © lectriques ( CISPR ), or the International Special Committee on Radio Interference.
- The Advisory Committee on Electromagnetic Compatibility ( ACEC ) coordinates IEC work in EMC between these committees.
- The International Organization for Standardization ( ISO ), which publishes standards for the automotive industry.
Among the major national organizations are:
- Europe:
- ComitÃÆ'Â © EuropÃÆ' Â © en de Normalization ( CEN ) or the European Committee for Standardization).
- ComitÃÆ'Â © EuropÃÆ'® en de Normalization Electrotechniques ( CENELEC ) or the European Committee for Elektrotechnical Standardization.
- The European Telecommunication Standards Institute ( ETSI ).
- United States:
- Federal Communications Commission ( FCC ).
- Automotive Engineers Association ( SAE ).
- Radio Engineering Commission for Aeronautics ( RTCA ); see DO-160
- English: Standard English Institution ( BSI ).
- Germany: Verband der Elektrotechnik, Electronic und Informationstechnik ( VDE ) or the Association for Electricity, Electronics and Information Technology.
Legal
Compliance with national or international standards is usually defined by laws enacted by individual countries. Different countries may require compliance with different standards.
In European law, manufacturers of electronic devices are advised to run EMC tests to comply with mandatory labeling of CE. The EU's 2004/108/EC (formerly 89/336/EEC) directive on EMC defines rules for the distribution of electrical devices within the EU. More is given in the EMC directive list.
EMC Design
Electromagnetic noise is produced at the source due to rapid current and voltage changes, and is spread through the previously mentioned coupling mechanism.
Due to a coupling line as effective at the beginning or at the end of the line, many aspects of good EMC design practice apply equally to potential emitters and potential victims. Furthermore, circuits that easily integrate energy into the outside world will easily integrate energy in and will be vulnerable. Single design improvements often reduce emissions and vulnerabilities.
Mem-ground and protect
Grounding and shielding aims to reduce emissions or divert EMI from victims by providing an alternative, low impedance path. Techniques include:
- Grounding or grounding schemes like earth star for audio equipment or ground planees for RF. The scheme must also meet safety regulations.
- Shielded cable , in which the signal cable is surrounded by an earthed, outer conductive layer on one or both ends.
- Sheltered home . A conductive metal house will act as an interference shield. To access components, such housing is usually made in sections (such as boxes and covers); RF gaskets can be used on joints to reduce the amount of interference leaked through the connection. RF gaskets are available in various types. Plain metal gaskets can be either braided wire or flat strips placed to create many tapering "fingers". If a waterproof seal is required, a flexible elastomer base may be impregnated with metal fibers which are dispersed into the interior or long metal fibers covering the surface or both.
Other common sizes
- Separate or filter at important points such as cable entries and high-speed switches, using RF chokes and/or RC elements. The line filter implements these steps between the device and the line. Techniques Transmission line for cables and cables, such as balanced differential signals and return paths, and impedance matching.
- Avoid antenna structures such as circulating current loops, resonance mechanical structures, unequal cable impedances or unfounded protectors.
- Eliminates the false rectifier connection that can form between metal structures around and near the transmitter installation. Such intersections in combination with an unintentional antenna structure can emit harmonic transmitter frequencies. Emergency depletion
- Avoid unnecessary redirection operations. The required shift should be done as slowly as possible technically.
- The noisy circuit (with many switching activities) must be physically separated from the rest of the design.
- High peaks can be avoided by using the spread spectrum method, in which various parts of the circuit emit at different frequencies.
- Harmonic wave filter.
- Design for operation at lower signal levels, reducing available energy for emissions.
- Fuses, travel switches, and circuit breakers.
- Temporary absorber.
- Design for operation at higher signal levels, reducing relative noise levels in comparison.
- Error correction techniques in digital circuits. This can be implemented in hardware, software or a combination of both.
- Differential signaling or other common-mode noise techniques for signal routing
- Aeroflex
- Anritsu
- Keysight (formerly Agilent and prior to Hewlett-Packard's test and measurement division)
- MILMEGA
- National Instruments
- Rohde & amp; Schwarz
- Tektronix
- Teseq (formerly Schaffner Testsystems)
- WÃÆ'¼rth
- Carries out electromagnetic interference
- Electrostatic discharge
- EMC (overground strength) issue
- EMC-aware programming
- Emergency conscious programming
- GTEM
- IEEE Electromagnetic Compatibility Society
- Immune-conscious programming
- International Commission for the Protection of Non-Ionization (ICNIRP)
- LISN
- List of common EMC test standards
- MIL-STD-461
- Spread spectrum
- Television Interference
- Automotive EMC Network
- European Commission EMC-Directive - Harmonious Standard for EMC
- EMC News and Blogs
- Emctest Technologies
- EMI Europe and EMC Assessment Compliance
- Federal Communications Commission
- IEEE EMC Society, Orange County, CA, Section
- IEEE EMC Society, Long Island Part
- News and information about Electromagnetic Compatibility rules
- Interference Technology - International Journal of Electromagnetic Compatibility
- EMC UK Compliance Club
- US. Telecommunication Certification Agency
- Radio Engineering Commission for Aviation
- A useful YouTube video explains what EMC is.
- FAQ About EMC
- EMC compliance FAQ
- Introduction to EMC
- Introduction to EMC & amp; EMI
- EMC and Regulatory Compliance Blog
- Introduction to EMC
- Introduction to EMC and inductive components
- The basics in EMC/EMI and Powerquality
- Analog, RF & amp; EMC Considerations in the Design of Printed Wiring Boards
- Application Notes: Design for EMC Compliance
- Design for EMC - Slot Via Effects, Split Planes, Gaps, and Refunds on Clock Signals
- Fundamentals of EMC Design
- EMC Design Guidelines
- EMC's engineering practice for panel builders
- EMC Resources (Clemson University)
- The Basics of Aircraft Electromagnetic Shield
- Standard EU summary by device type
Additional measures to reduce emissions include:
Hardening vulnerability
Additional measures to reduce vulnerabilities include:
EMC Testing
Testing is required to confirm that certain devices meet the required standards. This broadly divides into emissions testing and vulnerability testing.
An open air test site, or OATS, is the reference site in most standards. They are very useful for large equipment emissions testing systems.
However, RF testing of physical prototypes is most often done indoors, in special EMC test chambers. Room type includes anechoic, reverberation and gigahertz transversal electromagnetic cell (GTEM cell).
Sometimes a computational electromagnetic simulation is used to test virtual models.
As with all compliance tests, it is important that the test equipment, including the test chamber or any site and software used, is calibrated and maintained properly.
Typically, a series of tests provided for a particular piece of equipment will require the EMC test plan and test report follow-up . A full test program may require the production of some such documents.
Emissions test
Emissions are usually measured for emitted field strength and if appropriate for emissions made along wires and cables. Inductive (magnetic) and capacitive (electric) field strengths are near field effects, and are only important if the device being tested (DUT) is designed for locations close to other electrical equipment.
Usually a spectrum analyzer is used to measure emission levels of DUT in wide band (frequency domain). Special spectrum analyzers for EMC testing are available, called EMI test receivers or EMI analyzers. It combines the bandwidth and detectors specified by international EMC standards. The EMI receiver along with certain transducers can often be used for emissions that are carried and transmitted. Pre-selector filters can also be used to reduce the effects of strong out-of-band signals on the receiver's front end.
For emissions performed, typical transducers include LISN (channel impedance stabilization network) or AMN (artificial parent network) and RF current clamp.
For radiation emission measurement, the antenna is used as a transducer. Specific antennas specified include dipoles, bikonic, log-periodic, double-jointed guides and spiral conical spiral designs. Radiation emissions should be measured in all directions around the DUT.
Some more useful pulse emissions are characterized using an oscilloscope to capture pulse waveforms in time domain.
Vulnerability testing
Radiation field susceptibility testing usually involves a large RF or EM energy source and a radiating antenna to direct the energy to a potential victim or device under test (DUT).
Performing stress and current susceptibility testing usually involves a high-powered signal or pulse generator, and a current clamp or other type of transformer to inject the test signal.
Temporary immunity is used to test DUT immunity against powerline disturbances including spikes, lightning strikes, and switching disturbances. In motor vehicles, similar tests are performed on batteries and signal lines.
Electrostatic discharge testing is usually done with a piezo spark generator called an "ESD gun". Higher energy pulses, such as lightning or nuclear EMP simulations, may require large current clamps or large antennas that surround the DUT completely. Some antennas are so large that they are outdoors, and care should be taken not to cause EMP harm to the surrounding environment.
History
The earliest EMC problems are lightning strikes (lightning electromagnetic waves, or LEMPs) in buildings. Lightning rods or lightning conductors began to appear in the mid-18th century. With the emergence of power plants and widespread power supply lines from the late 19th century, problems also arose with the short circuit breakdown of equipment that affected electricity supplies, and with local fires and shock hazards when power lines were struck by lightning. The power plant is provided with an output circuit breaker. Buildings and equipment will soon be equipped with an input fuse, and then in miniature circuit breakers (MCB) of the 20th century will begin to be used.
As radio communications developed in the first half of the 20th century, interference between broadcast radio signals began to occur and an international regulatory framework was established to ensure interference-free communications.
As switching devices become commonplace, usually in gasoline-powered automobiles and motorcycles, but also in home appliances such as thermostats and refrigerators, temporary interference with domestic radio and (after World War II) TV reception becomes problematic, and in time legalized law requires suppression of the source of the disorder.
ESD problems first arise by accidental splashes of sparks in hazardous environments such as coal mines and when refueling aircraft or automobiles. Safe working practices must be developed.
After World War II the military became increasingly concerned with the effects of nuclear electromagnetic pulses (NEMP), lightning strikes, and even high-powered radar rays, on vehicles and mobile equipment of all kinds, and especially electrical systems.
When high levels of RF emissions from other sources become a potential problem (such as with the emergence of microwave ovens), certain frequency bands are set for Industrial, Scientific and Medical (ISM) use, which allows unlimited emissions. Various issues such as sideband and harmonic emissions, broadband sources, and the increasing popularity of electrical switching devices and their victims, resulted in steady development of standards and laws.
From the 1970s, the popularity of modern digital circuits grew rapidly. As technology develops, with faster switching speeds (increased emissions) and lower circuit voltages (increasing vulnerability), EMC is increasingly a source of concern. Many countries are aware of EMC as a growing problem and issuing direction to digital electronics equipment manufacturers, which specify the requirements of important manufacturers before their equipment can be marketed or sold. Organizations in each country, throughout Europe and around the world, are formed to maintain these directives and related standards. This regulatory environment led to sharp growth in the EMC industry supplying specialized equipment and equipment, analysis and design software, and testing and certification services.
Low voltage digital circuits, especially CMOS transistors, are becoming more prone to ESD damage because they are miniaturized, and new ESD regulatory regimes must be developed.
From the 1980s, the continued use of mobile communications and broadcast media channels has put great pressure on the airspace available. Authorities are pressing the band's allocations closer and together, relying on increasingly sophisticated EMC control methods, especially in the digital communication arena, to keep cross-channel interference to acceptable levels. Digital systems are essentially less vulnerable than analog systems, and also offer a much easier way (like software) to implement highly sophisticated protection measures.
Recently, even ISM bands are used for low-power mobile communications such as Wi-Fi and remote-operated door locks. This approach relies on intermittent ISM interference and the use of sophisticated error correction methods to ensure acceptance without loss during a quiet lull between interference bursts.
manufacturer of EMC (alphabetical) test equipment
See also
References
External links
Website
General introduction
Specific topics
Source of the article : Wikipedia
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