If you’re an electronic device manufacturer, it’s important to understand that your device — even if it may seem self-contained — can release waves that may disrupt other devices. This is known as electromagnetic interference, or EMI, and controlling it is a key part of compliance. 

The average home, office or industrial setting these days contains numerous electronic devices, from consumer electronics such as phones, tablets and computers to specialized equipment for manufacturing, measurement and specific business processes.

Understanding and controlling EMI is crucial for ensuring your device acts like a good neighbor within its shared environment, meaning it works as intended without causing disruption to other devices due to its electromagnetic radiation.

As specialists in electrical device testing, we can measure your device’s EMI and ensure that it stays within the limits set by regulatory authorities in the United States, European Union, or any other markets in which you plan to market your device.

To ask our team a question or request a quote for testing your device, contact us online or call us at 866-540-5287.

You can also learn more about how to measure electromagnetic interference below, from what electromagnetic interference is to topics like how EMI may affect your device’s compliance and the steps you can take to measure and control its output of electromagnetic emissions.

What is Electromagnetic Interference?

Electromagnetic interference is a term that’s used to refer to “noise” or interference that occurs in an electrical circuit caused by an external source. It can occur as a result of electromagnetic induction, electrostatic coupling, or conduction.

You may have heard of EMI as radio frequency interference. It can be natural or, more often, a result of electronic devices. When EMI occurs it can affect electronic devices and prevent them from working properly due to its effects on their internal components.

EMI can range from a minor annoyance to a serious problem. For example, you’ve likely seen (or, more accurately, heard) the results of electromagnetic interference when you use a phone near an amplified speaker or other audio equipment.

In some settings, EMI can be a major problem. For example, electromagnetic interference can prevent industrial machinery from functioning correctly, causing incorrect readings or potential safety issues, or cause performance problems with medical equipment.

Because of this, all major markets — including the United States, Canada, the European Union and many others — have regulations regarding the amount of interference an electronic device is allowed to produce before it’s considered unsuitable for the market. 

There are two major types of electromagnetic interference:

• Radiated electromagnetic interference. Radiated EMI is produced as a byproduct of radio frequency that’s picked up by other devices. This form of EMI travels through the air, meaning it can affect nearby devices even if they aren’t connected by a cable.
• Conducted electromagnetic interference. Conducted EMI travels through power and signal lines. For example, a device that’s connected to one electrical mains circuit could affect other devices that share the same mains circuit. 

Our guides to radiated emissions and conducted emissions provide more detail about the major types of electromagnetic interference, as well as how testing is performed to measure them. 

EMI and Regulatory Compliance for Electronics

Measuring and controlling EMI plays a major role in achieving compliance with regulations for your electronic device. As we mentioned above, all major markets have laws concerning limits on EMI produced by electrical and electronic devices and equipment.

In the US, these regulations fall under the scope of the Federal Communications Commission (FCC). In the European Union, there are various directives that govern the limits on emissions and interference from electronic devices. 

Measuring EMI from your device — and, more importantly, making sure it falls within the limits set under these regulations and directives — is a key step in getting compliance marks for your product and gaining market access.

FCC Part 15 Compliance

In the United States, the main regulation that governs electromagnetic interference — or, to be more precise — electromagnetic compatibility (the ability of electrical devices to work properly within a shared environment) is the Code of Federal Regulations, Title 47, Part 15.

Better known as the FCC Part 15 rules, this regulation sets limits on radio frequency emissions from devices. It also requires that any electronic devices are able to withstand a certain amount of interference from other devices without malfunctioning. 

Achieving compliance with FCC Part 15 is mandatory for almost all electronic devices that are sold in the United States. In other words, you need to demonstrate that your device isn’t going to cause excessive interference in order to legally sell it as a commercial product. 

However, some devices, such as industrial, scientific, and medical (ISM) equipment, fall under different regulations, such as FCC Part 18. 

Testing for FCC Part 15 involves measuring your device’s electromagnetic interference using a variety of techniques and metrics, including its radiated emissions and conducted emissions. It also involves measuring your device’s immunity to these forms of interference. 

EU Directives and Electromagnetic Interference

In the European Union and European Economic Area (the EU plus Iceland, Liechtenstein and Norway), electromagnetic interference is measured and regulated under a series of regulatory directives. 

The primary EU directive for electromagnetic interference is the Electromagnetic Compatibility Directive, or EMC Directive. The Radio Equipment Directive, which regulates radio equipment sold in the EU, also has requirements for measuring electromagnetic interference. 

How to Measure Electromagnetic Interference

So, if electromagnetic interference is a major problem, and controlling it is essential for gaining regulatory authorization and market access for your device, how exactly can you measure EMI and make sure your device is compliant?

EMI is measured during testing. Like other forms of electrical device performance testing, EMI testing requires the use of special equipment and a dedicated lab environment. 

This type of testing is usually divided into two types: pre-compliance testing, which is generally done early in the product development process, and more formal lab testing, which is done as part of the regulatory compliance process before bringing your device to market. 

Pre-Compliance EMI Measurement

Pre-compliance testing is a type of early-stage testing that’s carried out while you’re designing and developing your device. It helps you identify issues like electromagnetic interference early in the design process.

This can make changing your design cheaper and easier, since making changes at an earlier stage usually costs less and doesn’t require as much time as a late-stage change. 

Measuring EMI requires several devices, including the following:

• A spectrum analyzer (a device that measures and analyzes the strength of emissions from a device).
• An EMI receiver (a specific type of spectrum analyzer that measures electromagnetic emissions).
• Near-field probes (small probes that are used to visualize and locate where a device’s emissions are originating from).
• A pre-amplifier (a device that’s used to boost the signal strength of emissions, allowing for the detection of lower-level electromagnetic emissions).
• A Line Impedance Stabilization Network (LISN, a device that’s used to isolate a device from its power supply). 

Furthermore, pre-compliance measurement for electromagnetic interference requires a certain environment, namely, an anechoic chamber. This is a special testing environment that works to absorb reflections and allow for accurate measurements of radiated emissions from a device.

If you’re part of a large company, you might have access to the necessary test equipment and facilities to conduct in-house pre-compliance testing. 

However, most device manufacturers opt to work with a lab testing partner, as this allows for a simpler process and more accurate results. 

If you’re curious about the pre-compliance EMI measurement process and want to learn more, you can contact our testing lab to talk to our team about the necessary steps to measure your device’s electromagnetic emissions. 

Lab Testing for Electromagnetic Compatibility

In order to achieve compliance with FCC Part 15, the European Union’s EMC Directive, Radio Equipment Directive, or other national regulations for electromagnetic compatibility, you’ll need to complete lab testing for your device.

Lab testing offers a more formal assessment of your device’s electromagnetic interference than pre-compliance testing. It also involves extensive reporting of your device’s results, which plays an important role in achieving legal compliance and earning the FCC, CE or similar marks.

Lab testing for EMI includes conducted emissions testing, radiated emissions testing, as well as immunity testing, which assesses your device’s ability to function normally when it’s exposed to electromagnetic interference from other devices. 

As an ANSI-accredited testing lab, we offer a range of electromagnetic compatibility tests for all types of electronic devices. Our accredited lab scope page lists specific standards and tests we offer and provides more information about our services. 

Contact Us for Help With EMI Testing & Compliance

Measuring your device’s radiated and conducted electromagnetic emissions is a major step in the process of achieving compliance with FCC Part 15, the EU’s EMC Directive and other key standards for electronic devices. 

Emissions testing is one part of the formal process of electrical device testing, which needs to be completed before your device can earn the FCC Mark or CE Mark and legally go on sale in major markets. 

As an ANSI-accredited electronics testing laboratory, we can perform professional EMC testing for your device to help you achieve FCC, CE, ISED and other forms of compliance. 

We can also help you to determine which standards and regulatory compliance marks are most important for your device based on your device type and business objectives.

To request a quote for testing your device, or to ask our engineers and compliance specialists a question about any aspect of the process, contact us online or call us at 866-540-5287.