CS116: Transient Immunity Is Not RF Immunity

CS116 introduces fast-damped sinusoidal transients rather than continuous or steady-state radio-frequency energy. The test simulates transient disturbances that propagate through cables and wiring due to switching events, inductive loads, or external electromagnetic disturbances. These events are short but high in energy and can couple deeply into internal circuitry.

This test places primary emphasis on transient-protection strategies, including TVS diode selection and placement, power-input conditioning, and internal energy-dissipation paths. Designs that focus primarily on RF filtering and shielding often perform well under steady-state susceptibility testing but lack adequate protection against fast transient events.

Passing CS114 does not imply readiness for CS116. CS114 evaluates immunity to continuous RF current injection, while CS116 evaluates the system's ability to absorb and recover from impulsive energy without malfunction or damage. Failures during CS116 typically reveal marginal transient handling, insufficient clamping margins, or poor energy routing rather than deficiencies in RF filtering.