EMI RFI Mains Power Filters
EMI RFI Noise Filters are required in two situations, to prevent EMI from an Electronic Equipment Like A Dimmer, Thyristor Drive, SMPS or Switcher affecting other Modules in a System or Neighboring Equipment.
The Second Situation is when a Sensitive Equipment Like a Medical Apparatus or Precision Measuring Instrument has to be Immune to any Noise from outside, as it can affect performance.
Sometimes it is Accuracy that can get affected, but some electrical jolts can damage or desensitize fine sensors or positioning systems.