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Brief Introduction of Pre-EMI Civil Products CE Test System

Release time:

2023-04-11 15:16

Source:

　　1 Introduction

For electronic products, conducted harassment and radiation harassment are EMC testing items that must be passed. Radiation harassment is a big challenge for enterprises in terms of site and capital cost due to the need to build a standard three-meter anechoic chamber.

The usual test frequency range of conducted disturbance is 150KHz-30MHz. Some products such as lamps need to be tested from the lower frequency of 9KHz. In this frequency range, the electromagnetic environment of the space is relatively low, and the main reason affecting the bottom noise of the test comes from the power grid.

A standard conducted disturbance test usually includes the following equipment:

A,EMI receiver (or spectrum analyzer with EMI option)

B, artificial power network

C, pulse limiter (can be built in artificial power network)

D, the test environment that meets the standard test (shielded room or ordinary environment that meets the test bottom noise)

For enterprises, the construction of similar testing methods is more to conduct thorough testing in the research and development stage and better control the electromagnetic disturbance characteristics of products in the early stage of research and development. Therefore, how to adopt the most cost-effective scheme on the premise of ensuring comparability (consistency) with the test results of third-party laboratories as much as possible is a key consideration for each enterprise, especially in the initial stage of starting a business.

In the conducted disturbance test, artificial power supply network/pulse limiter are all equipment that must be purchased. As long as the test environment meets the system noise, shielded room or ordinary environment can be adopted. EMI receiver and spectrum analyzer (with EMI function) have relatively large price difference, which is also the biggest factor affecting the comparability of results. Therefore, it is necessary to compare the two in various ways, see if you can meet the consistency of the test results as far as possible under the premise of taking the best solution.

　　2 Comparison test

　　Summary of 2.1 comparison test instruments　　

Comparison test is divided into two steps:

The first step is manual operation, the overall layout is consistent, and the bottom noise and comb source are tested;

The second step is software operation, the overall layout is consistent, and the bottom noise and comb source are tested;

　　2.2 Manual Operation Test

　　2.2.1 Manual Test-Noise Bottom

　　

　　

The test layout is shown in the above figure, and the test results are shown in the following table:

　

Summary: The ESR/ESW bottom noise of the certified receiver is far below the standard limit line, which is a perfect test scheme. However, due to the relatively high price, it invests too much in research and development for enterprises. The bottom noise of FPC spectrometer itself is relatively high, the peak bottom noise is higher than 20dBμV in 150KHz ~ 5MHz, and even as high as 55dBμV in 150KHz frequency point, but it still meets the bottom noise of ordinary civil products below the limit of 6dB.

　　2.2.2 Manual Test-Comb Source

　　

The test layout is shown in the above figure, and the test results are shown in the following table:

Summary: The above test randomly extracts 6 test frequency points (PK value), and the test results deviate from the average value within 1dB.

　　2.3 Software Operational Test

　　2.3.3 Software Test-Noise Bottom

　　

The test layout is shown in the above figure, and the test results are shown in the following table:

　　

Summary: The ESR/ESW bottom noise of the certified receiver is far below the standard limit line, which is a perfect test scheme. However, due to the relatively high price, it invests too much in research and development for enterprises. The bottom noise of FPC spectrometer itself is relatively high, the peak bottom noise is higher than 20dBμV in 150KHz ~ 5MHz, and even as high as 55dBμV in 150KHz frequency point, but it still meets the bottom noise of ordinary civil products below the limit of 6dB.

　　2.3.4 Software Test-Comb Source　　

The test layout is shown in the above figure, and the test results are shown in the following table:

　　

Summary: The above test randomly extracts 6 test frequency points (PK value), and the test results deviate from the average value within 1dB.

　　3 Summary

In view of the testing in the research and development stage of the enterprise, that is, pre-compatible Pre-EMI, comprehensive test accuracy and cost considerations, recommend the use of spectrum analyzer (increase EMI option) program.

In the ordinary environment to conduct EMI (conducted disturbance) test, you may encounter the following problems:

A, the power supply of the test environment itself is relatively poor, which directly leads to the noise exceeding the standard and cannot be tested.

B,220V power supply has leakage protection, connected to LISN directly lead to office trip

C, there is no special site for long-term layout test

Under normal circumstances, R & D companies located in office buildings will encounter these or more problems, so how to quickly and efficiently carry out testing is very critical.

To this end, our company (Century Huize) has launched a full set of solutions, which have been taken into account in all aspects such as distribution filtering, grounding, EUT layout, etc., as shown in the following figure:

Advantages of the program:

A, Century Huize has completed the data comparison between the receiver and the spectrum analyzer by using its own laboratory, and the consistency is high;

B. Customized isolation and filtering integrated products, the input end can be directly connected to the 220V mains, and the output end can be directly connected to the product end for power supply, and they are all national standard sockets;

　　     According to GBT 6113.201/CISPR 16-2-1 standard, chapter 6.2: the test site shall be able to distinguish various emissions of EUT from environmental noise, and the environmental level

It shall be at least 20dB below the specified limit. During the field test, the ambient noise level shall be at least 6dB lower than the specified limit.

In this regard, our company recommend LISN front-end filter to ensure that the test environment meets the standard requirements.

C, the addition of isolation and filtering integrated products can not only ensure that LISN will not cause tripping, but also ensure that the bottom noise will not exceed the standard due to power supply problems;

　　     LISN used in CE test has relatively large leakage current. In order to ensure that the test does not affect the staff office, etc.

Division I introduced the isolation of power supply and filter integration products.

D, foldable ground plane, fully meet the requirements of the standard test and almost does not occupy the site in the case of folding;

　　     The bottom or back of the EUT shall be placed at a maneuverable distance of 40cm from the reference ground plane per GBT 6113.201/CISPR 16-2-1, Section 7.4.

The ground plane is usually a wall or ground, and it can also be a grounded metal plate of at least 2m × 2m (the boundary should exceed the boundary of EUT by at least 50cm, I .e.

can).

We have introduced a folding ground plane for the development of multi-site testing.

E,40cm high solid wood table, daily can be used to place instruments and equipment, can be used to place samples during testing, meet the standard test conditions.

　　     In accordance with GBT 6113.201/CISPR 16-2-1, Section 7.4, the actual layout is achieved as follows:

1. EUT is placed on an insulating material test bench at least 80cm high, which is 40cm away from any wall surface of the shielding room. (When the wall surface is used as the reference ground plane)

2. The EUT is placed on a 40cm high insulating material test bench, so that the bottom of the EUT is 40cm higher than the ground plane. (When the ground is the reference ground)

Our company has introduced a folding ground plane and a 40cm high test table for multi-site testing.

Through the optimized scheme, the test cost of the enterprise can be greatly reduced, and the R & D efficiency of the enterprise can be improved. The conducted harassment test can be carried out in the ordinary office environment (office building), and the results are highly comparable to those of the third-party laboratory. The conducted harassment plays a very key role in the power supply system of the whole product, and will also bring great help to the later radiation emission.

Century Wisdom (Suzhou) Testing Technology Co., Ltd

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