LISN for conducted emissions

Definition

A LISN, or Line Impedance Stabilization Network, is a device used to measure conducted emissions from electrical and electronic devices by stabilizing the impedance of the power line during testing. It plays a critical role in compliance testing by ensuring that measurements are accurate and repeatable, which is essential for meeting regulatory standards. By isolating the device under test from external influences and providing a known impedance, a LISN enables consistent evaluation of how devices emit electrical noise through power lines.

5 Must Know Facts For Your Next Test

1. A LISN typically has a specific impedance value, often 50 ohms, which is standardized for testing purposes.
2. It provides a means to connect the device under test to measuring equipment while filtering out unwanted signals from the power supply.
3. Using a LISN helps in complying with international standards such as CISPR 16-1-2 for conducted emissions.
4. LISNs are designed to minimize the impact of the test environment on measurement accuracy, ensuring that results reflect true emissions levels.
5. They are often used in conjunction with spectrum analyzers to analyze and quantify conducted emissions effectively.

Review Questions

• How does a LISN stabilize impedance during conducted emissions testing, and why is this important?
  • A LISN stabilizes impedance by presenting a consistent load to the device under test, which eliminates variations caused by fluctuations in the power supply or external noise. This stabilization is crucial because it ensures that the measured emissions are solely due to the device being tested and not influenced by external factors. By providing a known impedance, it allows for accurate and repeatable measurements that are necessary for compliance with regulatory standards.
• Discuss the relationship between conducted emissions and electromagnetic compatibility testing regarding LISNs.
  • Conducted emissions refer to electrical noise that can interfere with other devices through power lines, making it essential to measure them accurately. Electromagnetic compatibility (EMC) testing aims to ensure that devices can operate without causing or being affected by such interference. A LISN plays a key role in EMC testing by allowing for controlled measurement of these emissions, helping manufacturers ensure their products meet EMC regulations and function properly in real-world environments.
• Evaluate how the use of a LISN affects compliance with international standards in conducted emissions testing.
  • The use of a LISN significantly enhances compliance with international standards such as CISPR 16-1-2 by providing a controlled environment for measuring conducted emissions. This device ensures that all tests are performed under standardized conditions, which is vital for achieving reliable results that regulators accept. By minimizing external influences and stabilizing impedance, LISNs help manufacturers accurately assess their products' performance against stringent requirements, ultimately facilitating smoother market entry and improved product reliability.

Related terms

Conducted Emissions: Electrical noise that travels along the power lines of a device, potentially interfering with other electronic equipment.

EMC Testing:

Electromagnetic Compatibility testing ensures that electronic devices function correctly without causing interference to or being affected by other devices.

Impedance:

The total opposition a circuit presents to the flow of alternating current, combining resistance and reactance.