LISN for Conducted Emissions Testing

YAAN LISN products are measurement-network building blocks for conducted EMI testing. They create a controlled RF measurement condition at the EUT supply terminals while allowing operating power to reach the EUT. Selection must account for the supply system, current, voltage, network type, frequency range and measurement instrumentation.

LISN means Line Impedance Stabilization Network. It is a passive network placed in the EUT power path during conducted-emissions measurements. Its components establish a defined high-frequency impedance, reduce the influence of noise arriving from the external power source and couple disturbance from the EUT to a measurement port.

Without a controlled network, the impedance and background noise of a facility power connection can change the measured disturbance. A LISN improves measurement repeatability by presenting the intended RF impedance and providing a consistent receiver connection. It does not replace correct grounding, cabling, setup geometry or the procedure defined by the applicable test method.

Facility or DC source power enters the LISN and passes to the EUT through a network designed for the intended measurement. At radio frequencies, the network controls the impedance and routes EUT-generated noise toward the RF measurement port. An EMI receiver or suitable analyzer measures that coupled signal using the required detector, bandwidth and scan procedure.

The EUT is connected to the designated output while the supply is connected to the input. The RF measurement port connects to the EMI receiver through suitable coaxial cable and any required protection or transient-limiting accessory. Unused measurement ports, grounding and termination must follow the model documentation and laboratory procedure.

Conducted emissions testing evaluates unwanted RF energy carried on power or signal conductors. The LISN provides the measurement interface for supported power-line methods. Test limits, detector settings, frequency ranges and setup details depend on the applicable product requirement and must be verified by the responsible laboratory.

Identify the applicable measurement method and required network first. Then confirm AC or DC supply, number of conductors or phases, maximum EUT voltage and continuous current, frequency range, connector type, grounding, protection needs and measurement receiver interface. Select only from verified model ratings with suitable operating margin.

A LISN can store energy and may expose hazardous voltage depending on its supply and internal network. It must be installed, grounded, discharged and operated by qualified personnel according to its documentation and the laboratory safety procedure. Ratings and safety provisions are model-specific; this page is not a substitute for the operating manual.