As the name clearly suggests, EMI stands for Electromagnetic Interference. It is a generalization of an older terminology RFI (Radio Frequency Interference). EMI can be defined as an electromagnetic or electro static disturbance that causes malfunctioning or undesired response in one or more electronic system, equipment or circuit.
Recent studies and continuing evaluations have verified that no major/minor organization or a functional unit is totally free of EMI. It occurs when a system or equipment is unintentionally affected by electromagnetic energy. To exist, EMI requires an interfering signal source, a coupling path to the affected equipment or system and a system or equipment which is susceptible to the interfering signal. If we break/isolate anyone of the three, we can reduce/nullify the affects of EMI of that system.
You should keep it in mind that an EMI will only occur when all the three elements of this EMI triangle are available. This is also referred as golden rule of EMI.
The Interference Sources includes:
- Natural phenomena
- Transmitters (all types)
- Non – linear junctions
- Arcs (from slip ring assemblies, motor brushes, rotary joints, etc)
- Switching circuits
- Receivers
The medium for coupling includes:
- Direct radiation
- Indirect coupling
- Hard wire conduction
The susceptible equipments include:
- Receivers (all Types)
- Computers
- Audio systems
- Video systems
EMI problems range from minor disturbances to catastrophic equipment breakdowns. While acute occurrence can be easily recognized, they are not so common as the less severe, which are, nonetheless, quite capable of destroying a systems effectiveness. Generally moderate interference levels do not cause total loss of system operation but they can introduce inaccuracies and add considerably to operators as a normal occurrence during system operation because either they do not recognize the interference or they do not know that corrective control measures are available.
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