How to Reduce or Prevent EMI Noise in Electronic Devices

When a device circuit varies in magnitude or oscillates to a frequency level of 10 kHz or more, it creates electromagnetic interference (EMI) resulting in noise or disturbance. Any device using transistors and diodes when switched on and off so frequently emit electromagnetic waves. With the use of high-speed switching power supplies, it has become a major challenge nowadays. This is the reason you need EMI shielding material to reduce undesired noise in a control system or device causing disturbances. EMI may cause the Silicon Controlled Rectifier (SCR) to fall through in drives and damage the device beyond repair. To protect your devices and appliances, you need metal shields to control interference. In some situations, a twisted wire may solve the problem. However, when this method fails to work, take into consideration the following methods to check EMI noise in electronic devices and equipment:

Shielding

You can shut out unwanted electromagnetic fields and prevent it from damaging a device by using a shielded electronic enclosure. Most of them come with a metal shield to reduce unwanted noise. Though the efficiency of a shield depends on the material’s magnetic permeability, conductivity, and thickness, you can reduce noise significantly with a thin metal plate-like aluminum foil. It’s important to note that the impact of noise control or reduction for devices depends more on the methods of connection for enclosure formation than on the specifications of the materials used. When designers create openings in a shield to release heat, they reduce the maximum size of an individual opening than their total area. They keep every opening small to prevent electromagnetic waves from entering in and going out of the shield. That’s why EMI specialists prefer using plate materials with small multiple holes. Expanded or punched metals are ideal for shielding and ventilation.

Shielded Cables

Shielded cables help in breaking down the coupling effect between the signal and the noise. You can opt for coax cables for shielding purposes. A thin aluminum film foil or sprayed copper shielding is often found inside the plastic cover of a programmable logic controller (PLC) for protecting the electronic components in the PLC.

Fiber Optic Cable

In areas where noise pollution is high, experts prefer using fiber optic as it is one of the best solutions to eliminate noise. Though fiber optic proves expensive initially, it’s resistant to all forms of electrical noise.

Radio Frequency Chokes

You can use radio frequency (RF) chokes in power and data cables to protect devices from interference. If you look at portable device line cords, you will notice a split core choke near the line side input of that device or appliance.

Balanced Circuits

When you use a twisted pair of wire, you do not get rid of the noise. Instead, you couple it into the conductors, that is, the return and signal. This way, it’s subtracted as a common-mode noise, thus creating the balanced circuit that produces a higher impedance for the coupled noise or disturbance.

EMI shielding techniques entail covering the device completely or a circuit partially with metal shields from where the noise originates. The right choice of material will get rid of the noise and prevent it from radiating outside the electronic enclosure.

Elvis Moore is an active blogger with an extensive industry experience in the field of electronics and technology.