What is EMC Testing?
Electromagnetic compatibility, or EMC, refers to the ways that electronic equipment interacts with the electromagnetic environment around it. All electronic devices have the potential to emit electromagnetic fields, and many can be affected by the fields of other nearby devices or pieces of equipment.
Electromagnetic compatibility testing is an essential part of any electronic design project, and a necessary step before a product can be released on the market. Whilst the health and safety consequences of product malfunction are not usually very severe, there have been numerous cases where electronic devices have had to be recalled because of electromagnetic interference, costing manufacturers thousands of pounds.
EMC testing is used to ensure that a piece of electronic equipment meets the necessary electromagnetic compatibility regulations and will be safe to use around all other devices. In this article, we outline the reasons that EMC compliance is necessary and give an overview of the standards that need to be followed.
Why is EMC Testing Important?
The importance of EMC testing was first identified back at the start of the 20th century where it was discovered that faulty electric lamps could cause problems with the electricity in an entire neighbourhood when they were in use. This led to the creation of the first piece of EMC legislation, known as ‘The Lighting Clauses Act’ of 1899.
Nowadays, almost everywhere we go is inundated with different electrical devices. Whilst these developments have had many benefits, this also means that the potential risk for a product’s electromagnetic field to cause interference is high. EMC testing is now more necessary than ever to ensure that accidents are kept to a minimum and that high safety standards are maintained.
In everyday life, EMC testing means that our electronic communications are protected and things like television and phone calls cannot be interfered with. It also means that utilities can all be trusted to work simultaneously without any item malfunctioning and resulting in a hazardous situation.
However, in the case of medical, automotive and military industries, an issue with a piece of electronic equipment could be the difference between life and death. Safety-critical devices must pass rigorous EMC testing to be used in a variety of industries, and the failure to do so could have catastrophic consequences if a product was sold.
As well as ensuring that a product is safe to use, EMC regulations also ensure that electronic equipment meets a high standard of design and functionality. The different processes used in testing for EMC compliance will highlight any aspects of a product’s design that have the potential to cause problems, helping to iron out any issues before manufacturing.
Finally, complying with electromagnetic compatibility regulations is important because you stand the risk of being fined if a device is found not meeting the necessary safety standards. Not only could this cost your company a lot of money, it can also have an irreversible effect on your company’s reputation which could affect sales for many years to come.
What is EMC Compliance?
EMC compliance is the completion of all necessary tests that determine that an electronic product will not malfunction when exposed to electromagnetic radiation or cause any other nearby products to do so. Compliance is measured by confirming that all necessary standards have been met and all the health and safety checks outlined within these standards have been completed.
You will know whether an electronic product or device is EMC compliant in Europe if it is marked with a ‘CE’. This signifies that all standards have been met in the product development stages and that the product has been deemed safe to use.
Common EMC Standards
Here is an overview of some of the most common EMC standards that are used when testing for EMC compliance.
Also known as DO-160, this is an aerospace standard that outlines the procedures and environmental tests that are required for all categories of airborne vehicles. It contains guidance for testing the effect of factors like temperature, vibrations, power input and radio frequency on the performance of aerospace equipment.
This standard is recognized as the de facto international standard ISO 7137.
This is another aerospace standard that focuses on the effect of lightning on an aircraft by providing test waveforms that can be used to decide whether its electromagnetic field will be affected by lightning interference. It is used in conjunction with the SAE ARP5416A standard that outlines the procedures for carrying out lightning tests on aircraft electrical equipment.
This is the most common EMC standard used to test the electromagnetic compatibility of all non-aerospace vehicles such as boats and cars. It describes the correct test methods for measuring voltage transient immunity along with conducted and radiated emissions produced by automotive electronic equipment.
This international standard is one of the most widely used electromagnetic compatibility standards used in Europe because it applies to such a wide variety of electronic equipment. It outlines the emission requirements that are related to radio-frequency disturbances within a certain frequency range and advises what levels of emission are acceptable and how to measure them.
CISPR 16 is another of the most frequently used EMC standards. The publication specifies all of the approved equipment and methodology for measuring electromagnetic disturbances and a device’s immunity to them when the electromagnetic frequency is above 9 kHz.
This is an incredibly thorough standard and therefore is split into four different parts, with fourteen sections within this providing all the information required to carry out the all EMC tests outlined by the International Special Committee on Radio Interference (CISPR).
This standard is considered interchangeable with the CENELEC standard EN 55022, both of which define the methods of measuring conducted and radiated emissions, measurement equipment, measurement limits and the interpretation of the applicability of these limits. The standard applies to almost all commercial electronic devices, from household products like fridges to complex medical devices.
Plenty of the most frequently used EMC standards come from IEC 61000, which outlines many of the factors which can affect a device’s electromagnetic compatibility. IEC 61000-3-2 describes the limits of harmonic current emissions for different levels of electronic equipment.
IEC 61000-3-3 also describes emission limits, but in this case specifies the maximum voltage changes that a piece of equipment can produce under specified conditions. It also provides guidance on how to assess the performance of equipment during the testing of its voltage changes.
This section of the standard outlines the testing methods and immunity requirements of any electrical equipment that is subject to static electricity discharges. Within these methods, there are individual tests specified for different environments and installation conditions, and the whole standard aims to evaluate how well a product performs when it is subject to electrostatic discharge.
IEC 61000-4-3 is very similar to the previous standard, but in this case outlines the best ways to evaluate how a piece of electronic equipment performs when subject to electromagnetic fields that are radiated or radio-frequency. The tests described help to assess the immunity of the product.
Again, this standard looks at electronic equipment immunity when it is subject to electrical fast transients or bursts on its supply, signal, control and earth ports. Test procedures are outlined and figures are given to help establish levels of safety and acceptability.
In this standard, the test methods and immunity requirements are outlined for electronic devices that may experience unidirectional surges in the event of over-voltage from switching and lightning transients.
IEC 61000-4-6 again looks at the immunity of electronic equipment, but in this case it suggests test procedures to establish whether electromagnetic disturbance will occur when a radio-frequency field is nearby.
Similar to previous standards, IEC 61000-4-8 outlines the immunity requirements of electronic equipment when it faces magnetic disturbances at frequencies of 50 Hz and 60 Hz. Test levels, equipment and procedures are all listed within the standard.
The final common EMC standard is IEC 61000-4-11, used to harmonize the test methods and immunity levels for electronic equipment during voltage variations and dips and short interruptions.
This standard is one of the most important EMC documents in the medical industry and covers all of the basic safety guidelines for electronic medical devices when they are subject to electromagnetic disturbances. EMC safety tests and procedures are described referring to levels of immunity and how to establish these.
Whilst it can often feel like completing EMC testing is a perfunctory, time-consuming task, it is vital to ensuring that all electronic devices are safe to use and will not affect the performance of other devices around them. As more and more wireless technology becomes integrated into our lives these tests are more important than ever, and following all the relevant EMC regulations is the best way to ensure that your product or device will have no problems in the future.
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