Electromagnetic interference, also known as EMI, is a major source of concern to all engineers around the world since this has the capacity to possibly damage and cause harmful effects on all electronic items that we use daily. The exact effect of EMI on electrical items is not uniform but it is almost always harmful since we cannot imagine a life today without electronics.
What is EMI?
In very simple terms, EMI refers to the situation when electromagnetic waves from an outside source affects the internal working of an electrical system, and can cause minor interruptions as well as extremely major damage.
For example, the reason why we are asked to switch off our cell phones in an aeroplane is because EMI from the device can affect navigation signals. Electric static heard over phone calls is also caused by EMI. These are very minor damages, of course; however, sometimes EMI can cause very major damage such as harmful effects on military equipment or research materials, which can have very blinding impacts.
Electromagnetic energy can be of different types, and in order to know how to counter EMI, it is important to know what kind of energy we are dealing with. Electromagnetic energy mostly refers to:
- Gamma rays
- X- rays
- Ultraviolet rays
- Infrared rays
- Visible light
- Micro waves
- Radio waves
The effects of each of these are different. While visible light does not generally cause any kind of harmful effect, rays like gamma rays and infrared rays can jam up signals and cause major repercussions.
What is EMI shielding?
In order to protect equipment from sustaining damage, it is important to shield them with a protective coating that does not expose them to the harmful effects of EMI. EMI shielding can be of two types- RF shielding and magnetic shielding.
RF shielding- refers to the blocking of specific radiofrequency electromagnetic waves.
Magnetic shielding- this is a different type of shielding which is achieved by reversing the magnetic north and south poles or by separating the two magnetic items using a magnetic barrier, which will then redirect the magnetic field lines.
What are the materials that can be used for EMI shielding?
Not all kinds of materials can be sued for this because if they themselves react to EMI, then the whole purpose gets defeated. Shielding effectiveness should be taken into account while choosing a particular shielding material and this simply refers to the strength of the incoming EMI against the strength of the material.
The most common metals used for EMI shielding are aluminum, copper, nickel and steel. All of these are quite cost effective and resistant as well as have multiple practical applications. While all of them have their specific disadvantages, like the price of copper, corrosion of aluminum, ineffectiveness of steel against some kinds of rays, they are good options.
Mu metal is made from combining nickel with iron and is also a well known EMI shielding material.
Other than these, non metals such as silicone and neoprene are also used vastly as EMI shielding materials.