EMI (Electromagnetic Interference)

Introduction

Whether you’re an engineer at an original equipment manufacturer (OEM) looking to specify lights for a new vehicle, or an end-user looking to replace some lights on your vehicle, electromagnetic interference (EMI) is something you should know about.

If you’re not familiar with “EMI,” the term refers to a disturbance that affects an electrical circuit. If you’ve ever experienced reception issues with your AM/FM radio when your cell phone rings (or vice versa), that’s a perfect example of a problem caused by EMI. Lights can both cause and be the victim of EMI issues in your vehicle. For this reason, it is important to have a basic understanding of EMI and look for lights that have been adequately tested.

The Five Types of EMI

There are five main types of EMI that you should be aware of:

Radiated Emissions – Electromagnetic noise emitted by a light through the air that can interfere with other electronics (ex. cell phones, radios, etc.).
Conducted Emissions – Electromagnetic noise conducted down a power line in a vehicle which can interfere with other electronic components on the vehicle.
Radiated Immunity – The tolerance of a light to inbound electromagnetic noise in the atmosphere. Any broadcast signal (cell phone, radio tower, non-compliant electronics, etc.) can interfere with a light if it is not properly designed.
Conducted Immunity – The tolerance of a light to inbound electromagnetic noise conducted on vehicle power lines.
Electrostatic Discharge (ESD) – As a kid, you probably experienced shuffling your feet on carpeting and touching someone to give them a shock. This phenomenon is called electrostatic discharge (ESD) and can damage any electrical component – lights included.

Component Level vs. Vehicle Level

For OEM applications, lighting manufacturers focus on testing their products at a component (light) level. This is done to make sure that the lights will not cause a vehicle level EMI failure or interfere with other electronics on the vehicle. OEMs then test at a vehicle level to ensure that it meets regulatory requirements.
Standard vs. Custom Products

At J.W. Speaker Corporation, we design and manufacture both standard and custom products. For our standard products, we’ve established a set of high standards by which we design and test our products for electromagnetic compliance. For custom products, we design, test, and manufacture to meet your exact specifications. In the event that you do not have EMI specifications, we’ll provide you with our EMI standards to review and approve before we start on the design.