Electromagnetic Interference (EMI) and Electromagnetic Compatibility (EMC) are vital terms for product development and regulatory testing of electronic devices for companies all over the world, including Australia. Although these terms bear very different meanings, they are generally interchanged and the two have become easily confused.

It is a common misconception that electronics are closed systems. However, any electronic device produces an amount of electromagnetic radiation and the electricity that flows through these systems in the circuit and wires, is never completely contained. The energy that these devices emit, called electromagnetic radiation, can circulate through the air or even be conducted through power cables, and this is usually referred to as ‘disturbance voltages’.

When releasing a product into the market, it is imperative that the product withstands a wide range of industry level tests in which EMI and EMC levels are analysed to ensure the compliance of the product.


EMI is defined as the electromagnetic energy that interferes and affects the function of an electronic device. Although EMI can sometimes occur naturally through environmental elements and events, such as electrically charged storms and radiation from solar, usually the source of EMI is generated from another electrical device or electrical system.

EMI can be caused by a multitude of electronic devices, however, certain devices and elements create a greater disturbance than others. Devices such as industrial machines and intentional radiators such as mobile phones and smartphones are the biggest and commonest contributors to EMI interference.

For these machines to operate efficiently and as electronic devices rarely operate in solidarity, these devices are developed to operate in the presence of EMI energy.


EMC is the measurement of the ability of a device to operate in its regular capacity in a shared operating environment at the same time as other devices, without affecting the regular operating ability of other devices in the same environment.

The evaluation of devices on how they will react when they are exposed to an environment with high levels of electromagnetic energy is a component of this type of testing and is most commonly known as immunity or susceptibility testing. Radiated immunity CE mark EMC testing for Europe

Another measurement of EMC that is known as emissions testing, is the measurement of EMI that is generated by the internal electrical systems of the device.

Both of these aspects are crucial to the design, engineering and manufacturing analysis of an electronic device. The failure to adequately and accurately anticipate the EMC of an electronic device can have caused a lot of negative consequences. These consequences include safety risks, the failure of the operation of the device and loss of data. The testing of equipment for EMC and EMI is essential in the development stages of creating a device to understand how it will operate in conditions in the real world.

Engineering and design considerations
Electronic products that have gone through the engineering and development process should meet the EMI/EMC limits that have been developed by regulatory bodies. It is important that this is done prior to the products being launched into the public domain for consumers to purchase. If proper manufacturing guidelines and standards have been followed at the engineering and design stage, the product will be able to pass this testing. If the electronic component fails, particularly after purchase, this poses a number of serious problems including personal safety risks, loss of important data and ultimately, product failure.

As part of the engineering and design process, some manufacturers actually use EMI/EMC compliant components. If this is done, it can save a lot of re-work that may potentially be required if these components fail the EMI/EMC test, particularly once the products reach the final manufacturing stage. It is important for the designer to consider specific industrial or military standards for the components of the product that is being developed, as these already comply with the manufacturing standard.

Compliance requirements

There are various manufacturing standards such as ISO, IEC and CISPR that define acceptable limits of EMI and overall EMC. There has also been a wide range of testing equipment to measure EMI/EMC levels, which helps to give engineers a better understanding of how a device or product my behave once purchased by the consumer.

For certain industries, this testing is actually a requirement, but this isn’t the case across all industries. However, it is widely recognised that one of the best ways to identify EMC issues early in the product engineering and development process, is to use compliant components. This can save the product manufacturer massive amounts of time and money, as well as reduce many of the risks highlighted earlier.

If you want to be sure that your electronic device is up to standard, it is important to ensure that it has passed EMI and EMC testing before you purchase it.

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