Transient Limiter for Protecting Spectrum Analyzer
Transient Limiter Limits input voltage when conducted EMI emissions measurements are conducted using Line Impedance Stabilization Network (LISN).
Transient Limiter is connected between the EMI measurement instrument input and RF output port of LISN. The Transient Limiter blocks the supply voltage from the LISN RF port but allows the RF signal to pass without much attenuation, so that it can be measured with an EMI receiver.
Because the RF signal must be passed through, any short transients (a few microseconds or less) on the power supply lines will also be passed through. Transient limiter LIT-930A protects the EMI receiver input from these short transients. A transient with high enough energy could badly damage an unprotected receiver input.