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A Brief Guide to EMI RFI Shielding Techniques

We are surrounded by electromagnetic fields, they are everywhere. We cannot see them and we cannot hear them so unless they are causing a problem, it is not something that we necessarily focus upon.

Every electric or electronic device emits electromagnetic radiation and some of the electromagnetic radiation comes from natural sources.

In a world where most of us use laptops, mobile phones, tablets, TV and more, our ever increasing use of technology is creating more and more in the way of electromagnetic radiation.

You may become aware of electromagnetic fields as they can cause interference between technological devices, you may notice a noise or a picture interference on a device and the problem can cause devices to function below capacity, can cause damage to the device or cause it not to function at all. For example if you place your cell phone beside the speakers for your computer, the speakers may hiss or buzz. Industry, business and government departments have to be increasingly aware of the potentially very serious risks to security equipment, hospital life saving equipment, controls for aviation and transport and in fact devices across the entire infrastructure. EMI RFI shielding techniques can simply be a nuisance or it can be potentially life threatening. Many people are concerned regarding the effects that exposure can have for their health.

This interference is known as electromagnetic interference (EMI), or if it is in the radio frequency range, (RFI). EMI travels along wires and circuits while RFI is the noise which travels as radio waves.

It is essential that devices have the capacity to work properly and as such most countries have introduced certain requirements for devices. They must be able to work correctly when they are subjected to an amount of EMI and the requirements also state that a device should be ‘insulated’ in a way so as not to emit beyond a certain measured amount of EMI which could interfere with other devices. Manufacturers must comply with the requirements.

The process by which devices can work alongside each other is known as electromagnetic compatibility (EMC). In order to achieve electromagnetic compatibility, a technique known as electromagnetic shielding has to be employed.

EMI shielding techniques are used to effectively isolate the device from the effects of external EMI sources and to prevent the device interfering with other devices, by providing a barrier. Electromagnetic shielding uses a specialist type of material capable of blocking out the electromagnetic fields. Metals such as copper, aluminium, stainless steel and zinc can be employed for this purpose.

Shielding is used on cables and also on enclosures.

Shielding techniques include

  • Enclosing equipment in a material which is capable of absorbing EMI
  • Using a coating which can be sprayed on the enclosure of a device
  • The use of filters which are designed to block the incoming and outgoing interference
  • The use of gaskets which can be made of rubber materials and used to seal joints
  • RF absorbing materials for RFI
  • Fabric combined with a metal can be used to protect rooms
  • Using wire devices can be used to protect yourself as can minimising the number of devices that you use
  • Keeping a distance between you and the devices that you use

Different devices will require different techniques and materials and it is a matter for the professionals to decide on the most appropriate technique or material for the purpose.



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Written by Nathaniel Fried

Co-founder of Fupping. Busy churning out content and building an empire.

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