Electromagnetic interference is a prevalent problem for engineers. As manufacturers continue the miniaturization movement, the devices and components we make become more susceptible to electromagnetic interference (EMI). Therefore, the need to deflect interference around and away from delicate systems is only growing.
There are a few different ways to help reduce EMI, which we will be covering in this article.
Ways to Reduce EMI
When we’re talking about electromagnetic interference, we often refer to an emitter device and the victim device. This isn’t always the case, since there are natural causes of EMI, too.
Sometimes, reducing a device’s exposure to EMI is as simple as moving one of these two devices so there’s more space between them. However, the better solution is to include a solution in the initial design.
There are three different methods to help reduce EMI: filtering, grounding, and shielding. Let us now take a look at each of these and understand what each solution entails.
Filtering
One way to minimize EMI is to filter out unwanted signals.
Filtering prevents bad signals from entering the power supply of what would otherwise be the emitter device. It is most commonly used with cables and connectors on lines into and out of a circuit. In effect, the filter works as a choke to block unwanted EMI while letting desired signals to pass through.
Filtering can be a viable choice for electronics and aerospace manufacturers when they can control which signals to emit and which ones to block.
Grounding
Grounding establishes a conductive path for the signal to travel. It will connect an electronic element of a system to a destination point (such as the earth itself).
For those choosing to ground their systems, there are some notes they should be aware of:
- Keep leads away from internal circuits.
- Use multiple grounding points.
- Isolate circuits from ground if ground loop voltage can’t be controlled any other way.
- Maintain separate groups for analog and digital circuits.
Shields come in all shapes and sizes, depending on your needs.
Shielding
A shield encases the devices within an enclosure. It acts as a deflector, an absorber, or both to keep the device inside safe from the damaging effects of EMI.
Shielding is the most common way of deflecting interference for both emitters and victim devices. These shields are made of ferromagnetic metals and are proven to be a versatile solution in cases where electromagnetic interference is a concern for manufacturers.
Shields can be seen in a wide variety of industries, including medical, aerospace, electronics, telecommunications, and automotive.
Types of Magnetic Shields
Several types of shielding techniques can be used to protect equipment and instruments from the effects of magnetic interference. So, let’s look at the 4 most common types of magnetic shielding. Different applications and needs will call for different types of shields, but the types of shields can be combined if the situation calls for such a solution.
High-Permeability Alloys and Coatings
High-permeability materials, such as certain alloys and coatings, can mitigate EMI. They can be applied through several different methods including electroplating, dip coating, chemical vapor deposition, and physical vapor deposition.
When referring to high-permeability alloys or coatings, we’re talking about materials that attract and redirect magnetic field lines through themselves effectively.
These layers are often only micrometers thick but offer significant protection against EMI. Different types of coating materials include metallic, ceramic, or composite-based substances tailored to the device or the environment it operates in. This protective function is due to the high magnetic permeability of these materials.
Magnetic Shields
Magnetic shields are our specialty here at Eagle Magnetic. Different types of sheet metals—including stainless steel, nickel, copper, and iron—are cut and shaped to enclose the device within.
Designing and manufacturing a shield is a complicated process, requiring expertise and specialist equipment. However, it is a cost-effective solution and one proven to deflect and absorb EMI that can threaten systems of all shapes and sizes.
Active Magnetic Shields
Once the magnetic shields mentioned in the previous section are put in place, their functions are invisible. So, they are considered passive shields—a misnomer considering all the work they’re actually doing.
Active shields make use of electromagnets to create their own magnetic field to cancel out external fields.
While this is an effective method for shielding against high-frequency magnetic fields, these shields are more expensive than passive shields because of a more complicated construction and control system.
Superconductors can be used to counter EMI, but this is an expensive solution and not suited for all situations.
Superconducting Shields
Finally, we have superconducting shields. These are excellent conductors for both electrical and magnetic fields.
Superconductors conduct electricity and transport electrons from one atom to another. However, to do so, the material must be very cold—cryogenic, in fact. In order to work, some superconductors need to be as cold as -183°C (-297°F).
This does represent the biggest downside of superconducting shields. It is expensive and difficult to reliably maintain such a frigid temperature in anything but the most controlled environment.
Create the Magnetic Shield You Need with Eagle
More often than not, going the route of a traditional magnetic shield is the right call for your project. Not only is it the most cost-effective approach, but it is also the one with the most research and development behind it. The processes behind making a magnetic shield are the most well-documented and most reliable, so when you can’t leave it to chance, go with what’s proven.
Creating the right magnetic shield for your devices needs to be an intentional, considered process. Choosing the right team for the job is a critical first step.
The team at Eagle Magnetic has been making magnetic shields for over 50 years, so when you need reliability, expertise, and trust, you know Eagle is on your side. Ready to get started? Contact us today.
