LISN, EMI Receiver & Test Setup
Two pieces of equipment make conducted-emission testing possible: the LISN, which isolates the EUT from mains noise and diverts a calibrated fraction of the EUT's own noise into a measurement port, and the EMI receiver, which sweeps that signal across frequency. This module opens both up and shows how a full test bench comes together.
A LISN (Line Impedance Stabilization Network) does two jobs at once: it presents a fixed, standardized impedance to the EUT so measurements are repeatable across labs, and it diverts a defined fraction of the EUT's noise current into a calibrated 50 Ω port feeding the receiver — while blocking noise coming from the mains supply itself from contaminating the measurement.
| Component | Typical Value | Purpose |
|---|---|---|
| Blocking inductor (L) | 50 µH (per CISPR 16-1-2) | Blocks mains-side noise; forces EUT noise toward the measurement port |
| Coupling capacitor | ~0.1–8 µF | Couples the EUT's noise current into the 50 Ω measurement path |
| Measurement resistor | 50 Ω | Provides the calibrated impedance the EMI receiver expects |
| Termination resistor (unused port) | 50 Ω | Terminates the port not currently feeding the receiver, so it doesn't distort the measurement |
Click each control below to see what it does on a live sweep.
A repeatable CE test needs more than a LISN and receiver: the EUT sits on an insulated table above a bonded ground plane, is fed through an isolation transformer to keep facility mains noise out of the measurement, and every metal enclosure on the bench is bonded to the same ground reference.
Module 5 Quiz
Select the best answer for each question. Instant feedback is provided after each response.