EMC Part 67. Conducted Immunity Via CDN (Coupling-Decoupling Network) & Capacitive Coupling Clamp.

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A conducted immunity test measures a device's ability to withstand disturbances that travel along power lines or signal cables. These disturbances can lead to malfunctions, performance degradation, or even complete failure. The purpose of a conducted immunity test is to ensure that the device remains unaffected by such disturbances and maintains its performance. These tests evaluate the potential impact of electromagnetic interference on a device's functionality. The results are used to ensure product reliability and for certification purposes.

The levels of interference traveling down these lines vary based on the associated E-Field or H-Field to which the equipment is exposed.

When testing immunity to conducted RF noise or interference, several injection and test methods can be employed. The most common method, as depicted in the image below, involves using the substitution method with a coupling decoupling network (CDN) injection device. Additionally, the injection of EFT pulses onto data lines is typically accomplished through a capacitive coupling clamp.

Testing with a CDN (Coupling-Decoupling Network) or Capacitive Coupling Clamp are both techniques used in electromagnetic compatibility (EMC) testing to inject signals into or couple signals with the equipment under test (EUT). However, these methods differ significantly in their application, functionality, and typical use cases.

Coupling-Decoupling Network (CDN):
Purpose: CDNs are used to inject conducted radio-frequency (RF) disturbances (e.g., common-mode signals) into cables connected to the EUT while ensuring that the unwanted signals are not back-fed into auxiliary equipment or the power supply.
Applications:
Conducted immunity testing (e.g., per IEC 61000-4-6).
Coupling RF disturbances to signal, data, or power lines of the EUT.
Isolates auxiliary equipment from the injected RF signals.
Operations:
The CDN is inserted between the EUT and its connected cables.
It provides a controlled impedance and consistent injection point for the RF signals.
The decoupling part ensures minimal disturbance to the rest of the test setup.

Advantages:
Provides consistent and well-controlled signal injection.
Reduces variability in test results due to environmental factors or cable configurations.
Easy to set up for certain standardized tests.

Limitations:
Limited to systems with specific cable types that match the CDN (e.g., Ethernet, coaxial, or multi-core cables).
Requires physical interruption of the cables to insert the CDN.

Capacitive Coupling Clamp:
Purpose: The capacitive coupling clamp is used to inject RF signals into the EUT's cables in a non-intrusive way, typically for conducted immunity testing.
Application:
Conducted immunity testing (e.g., per IEC 61000-4-6).
Used when inserting a CDN is impractical (e.g., for shielded cables or large setups).
Operation:
The coupling clamp is placed around the cable connected to the EUT.
It capacitively couples RF disturbances into the cable without direct electrical contact.
Works by creating a capacitance between the clamp and the cable, allowing RF energy to couple inductively.

Advantages:
Non-intrusive; no need to disconnect or interrupt cables.
Useful for setups with non-standard cable configurations or when CDNs cannot be used.
Flexible and can handle larger cable diameters or multiple cables.

Limitations:
Less precise than a CDN due to variability in coupling efficiency (depends on cable shielding, length, and geometry).
Coupling efficiency may need to be calibrated for each test setup to ensure compliance with standards.

In summary, CDNs are preferred for controlled, precise applications with standard cables, while capacitive coupling clamps are ideal for non-invasive testing, particularly for non-standard or shielded cables.

[technologiesdiscussion]

Thank you for watching this video.
There are two methods to perform Conducted Immunity (CI) testing. The first and preferred method is via a CDN (Coupling-Decoupling Network). The second method involves using a clamp to couple the noise source directly to the conductor of the cable.
For more information, please refer to this video. Thank you.

[avinashgowda]

please do the video on harmonics and flicker test

[emc]

Perfect explanation ! Thanks very much !

[ThànhTôn-kv]

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