### 2.3.5 Preventing Electromagnetic Interference

All interference sources, either from outside or inside of the equipment or application system, affect the equipment by capacitive coupling, inductive coupling, or electromagnetic waves. Electromagnetic interference (EMI) occurs due to radiated interference or conducted interference, depending on the transmission path. When the energy, often RF energy, from a component arrives at a sensitive component through the space, the energy is known as radiated interference. The interference source can be either a part of the interfered system or a completely electrically isolated unit. Conducted interference occurs when interference is transferred from one unit to another unit through cables, which are usually electromagnetic wires or signal cables connected between the source and the sensor. Conducted interference often affects the power supply of the equipment, but can be controlled by a filter. Radiated interference may affect any signal path in the equipment, and is difficult to shield.

The anti-interference requirements for the equipment are as follows:

l Take interference prevention measures for the power supply system.

l Keep the switch away from the grounding system or surge protection grounding system of the power facility.

l Keep the equipment far away from high-frequency current equipment such as high-power radio transmitting stations and radar stations.

l Take electromagnetic shielding measures when necessary.