EMC conducted test is one of the testing parameters on EMC test, beside the radiated test. This testing is required in order to ensure that electronic devices already met the requirements of EMC standard. EMC conducted is more focus on electromagnetic emissions produced from the power cable to the power source, which can affect the functionality of other devices around it.
In this article we will discuss everything you need to know before performing the conducted emission test for EMC requirement.
What is conducted emission test?
Basically, conducted emission test is an activity of measuring the amount of electromagnetic energy produced by electronic devices and delivered from the power cable to the power source. The emissions produced can interfere with other devices that connected to the same power source.
Conducted emission test is usually performed in the frequency range of 150 kHz to 30 MHz. In this frequency range, it should be ensured that the power source remains relatively clean and does not interfere with other devices around it.
Conducted emission testing process
Conducted emission test for telecommunication device is carried out in the appointed EMC laboratory by DJID. The testing process should refer to international standard of CISPR32. The following activities are related to the conducted emission testing process.
Testing setup
The device under testing (DUT) is placed on a special table or you can keep on the floor if the DUT is quite big. Below is the testing setup of EMC conducted emission test.
- LISN (Line Impedance Stabilization Network) is placed between the power source and the DUT. LISN helps to create a uniform impedance and filters out unwanted noise from the power source.
- Spectrum analyzer (EMI test receiver) is connected to the LISN to measure electromagnetic noise generated by the DUT.
Device classification
DUT is divided into two class categories based on their using environment.
- Class A is for device used in commercial or industrial environments, such as medical and automotive devices.
- Class B is for device used in household environments, such as home appliance devices.
Testing limits
The frequency range for conducted emission measurements are in 150 kHz – 30 MHz. Below is the conducted emission limits for class A and B.
| Frequency range | Class A Limits: Quasi-peak |
| 0.15 – 0.5 MHz | 79 dB(μV) |
| 0.5 – 30 MHz | 73 dB(μV) |
| Frequency range | Class B Limits: Quasi-peak |
| 0.15 – 0.5 MHz | 66 to 58 dB(μV) |
| 0.5 – 5 MHz | 56 dB(μV) |
| 5 – 30 MHz | 60 dB(μV) |
As you can see on the table above, the emission limits for class B are much stricter than class A. This is because the number of devices used in household environments is much bigger in number than in industrial environments.
Failed during conducted emission test
The conducted emission test does not always pass, it can be failed in some cases. We can simply see from the graph of conducted emission test result, the exceed graph will indicate that the testing is fail. A common reason of failing during conducted emission test is because a poor quality of AC-DC power adapter.
Poor quality of adapters tends to produce higher levels of emissions. Possibly the poor quality of adapters is due to defects during the production process.
In other cases, it may adapter manufacturer performs quality control testing with DC power source. Meanwhile, the conducted emission testing is performed by using AC power source, which may produce different results of emission level compared to the quality control test result.
Tips for passing conducted emission test
Here are some preventive action from testing fail before performing the conducted emission test:
Choose a good quality power adapter
The quality of the adapter will determine the result of conduction emissions produced by the device. It is also important to match the type of power adapter to be used with the class of the device.
Prepare alternative power adapter
It is important to bring several adapter options when performing a conducted emission testing at the EMC laboratory. If one adapter fails, it can be replaced with another adapter. This will save time and money during the testing process.
If you have any question related to DJID certification, please don’t hesitate to contact us by sending enquiry to info@narmadi.com.
