Lisn

Definition

A LISN, or Line Impedance Stabilization Network, is a specialized device used in electromagnetic interference (EMI) testing to stabilize the impedance of power lines and provide a consistent measurement environment. By ensuring that the impedance seen by the device under test (DUT) is uniform, LISNs help accurately measure conducted emissions and immunity levels, enabling compliance with regulatory standards.

5 Must Know Facts For Your Next Test

1. LISNs are crucial for ensuring that measurements taken during EMI testing are reproducible and consistent by providing a stable reference impedance.
2. The standard frequency range for LISNs typically covers from 150 kHz to 30 MHz, which aligns with common conducted emissions testing requirements.
3. LISNs can also isolate the DUT from the mains power supply, helping to prevent unwanted feedback during testing and ensuring more accurate results.
4. In addition to stabilizing impedance, LISNs often include built-in filtering capabilities to reduce noise and improve the quality of measurements.
5. When using a LISN, it is important to follow specific standards, such as CISPR 16-1-2, which outlines the proper setup and use of LISNs for EMI testing.

Review Questions

• How does a LISN contribute to accurate conducted emissions testing?
  • A LISN plays a vital role in conducted emissions testing by stabilizing the impedance seen by the device under test (DUT). This stabilization ensures that the measurements reflect the true emissions from the DUT without interference from fluctuating impedance levels. By providing a consistent measurement environment, LISNs help engineers obtain reliable data that can be compared against regulatory standards.
• Discuss the key features of a LISN that enhance its functionality during EMI testing.
  • Key features of a LISN that enhance its functionality during EMI testing include its ability to stabilize impedance and isolate the DUT from mains power. This isolation prevents feedback that could distort measurements. Additionally, many LISNs come equipped with filtering capabilities to minimize noise, leading to clearer readings. Compliance with established standards like CISPR 16-1-2 ensures that these devices perform optimally and reliably during tests.
• Evaluate the impact of using a LISN on the overall process of achieving electromagnetic compatibility (EMC) in electronic devices.
  • The use of a LISN significantly impacts the process of achieving electromagnetic compatibility (EMC) in electronic devices by providing precise control over testing conditions. By ensuring stable impedance and isolating devices from noise during measurements, engineers can accurately assess a device's emissions and immunity characteristics. This leads to better design choices that enhance EMC performance and compliance with regulations. Ultimately, the effective use of a LISN streamlines the development process, reduces time-to-market for compliant products, and improves reliability in real-world applications.

Related terms

EMI:

Electromagnetic interference, which refers to the disruption of electronic devices caused by electromagnetic fields generated by other devices.

Conducted Emissions: Unwanted electromagnetic energy that travels along conductive paths, such as power or signal lines, potentially affecting other equipment.

Measurement Receiver: A device that captures and analyzes signals for EMI testing, used in conjunction with LISNs to evaluate the performance of electronic devices.