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The necessity of the construction of automotive EMC laboratories for car companies

1. The necessity of building an automotive EMC laboratory

With the increase in the number and type of automotive electronic equipment and the increase in operating frequency, the electromagnetic environment in automobiles becomes increasingly complex. At the same time, electronic devices and devices in automobiles, especially semiconductor logic devices, are very sensitive to electromagnetic interference, and electronic devices in automobiles often interfere with each other. Even so, the wide application of automotive electrical equipment is still increasing, and its internal electromagnetic environment will become worse, resulting in more severe electromagnetic compatibility interference.

Any foreign electronic product must undergo performance testing and testing EMC testing before being applied to automobiles; Before commercialization, strict matching testing and the most critical matching testing EMC certification must be conducted. For electronic products that have not been strictly tested, no complete vehicle will be used, which is also the key to the difficulty for domestic enterprises to enter the foreign automotive parts supply chain. EMC involves the safety and reliability of complete vehicles, so foreign automotive companies do not easily use component products for reliability testing.


2. EMC Lab Construction Plan

Talking about the planning and construction types of automotive EMC laboratories, except for adding vehicle hub systems, there are only scale differences in vehicle level laboratories. Both laboratories include a test environment and a test system. The semi anechoic chamber required for automotive EMC testing is called an anechoic chamber. The testing system is divided into EM and EMS testing systems, namely, electromagnetic interference testing and electromagnetic interference testing.


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2.1. EMC Test Environment Planning

Half of the anechoic chamber of the test environment is generally composed of anechoic chambers, while the control room is composed of anechoic chambers The composition of the power amplifier. The anechoic chamber is a shielding chamber with a wave absorbing material inside. The function of the shielding room is to prevent outdoor electromagnetic waves from entering the interior of the laboratory and block the transmission of electromagnetic waves inside the laboratory; The function of the absorbing material is to absorb the electromagnetic waves emitted by the tested components in the laboratory to avoid errors in the test results caused by reflection; The control room is used to place fully compatible receivers, signal generators, monitoring computers, and other equipment to complete the monitoring of the test process and results; The power amplifier is placed in the power amplifier room. The power amplifier itself has strong radiation and is harmful to human health, so it is placed separately.

The anechoic chamber itself is an open place, simulating an open space without electromagnetic interference. Therefore, EMC Lab recommends building it in a relatively quiet, vibration free, and strong electromagnetic environment. At the same time, it is specifically built for automotive components or complete vehicles, and the EMC smoke exhaust problem must be considered in the laboratory. For automotive components, EMC Lab recommends leaving a waveguide on the darkroom wall to provide a photoelectric transmission channel or facilitate the introduction of compressed air pipes. Waveguides will play an important role in future experiments. Because the control room is also equipped with telephone filters and signal filters, and because the control room is also a shielded room, the installation of these two filters can solve the problem of communication with the outside world.


2.2. EMC test system planning

The selection of EMC testing systems will directly affect the testing standards and laboratory testing capabilities that can be completed, so targeted research and selection is particularly important. Relevant standards formulated by EMC international standards, regions, and standardization organizations, such as the Automobile Industry Association. EMC has been developing this standard for approximately 50 years since the 1960s. The standards of each standard organization basically include vehicle and component testing standards, and there is a corresponding reference relationship between each standard. That is, in addition to differences in the rigor of the standards, there is also a trend towards convergence in testing content and methods.

The standards developed by CISPR and ISO cover all types of automotive EMC. At the same time, the testing content also provides a model and foundation for other regional organizations and enterprise standards.

ISO and CISPR develop relevant vehicle EMC standards in Table L below, including:


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In addition to differences in the rigor of standards, there is also a convergence in testing content and methods, which also provides opportunities for companies or institutions that are relatively short of funds to gradually build. At this point, it is necessary to consider in detail in the planning which equipment must be in place at once and which equipment can be gradually improved. For the test system we are discussing, if we plan to gradually implement it, we can consider coordinating the test project or test intensity. For example, we can separately list transient interference and anti-interference equipment outside the dark room, separately list electrostatic discharge equipment, or gradually purchase expensive power amplifiers.


3.Issues needing attention in the construction of EMC laboratory

Due to the fact that project implementation generally involves the separation of environment and system, issues that should be noted during the respective construction or selection process are also discussed here.


3.1. Precautions in the construction of EMC test environment (semi anechoic chamber)

Before construction of a semi anechoic chamber, the following requirements must be met:

(1) The 3-meter method darkroom L * W * H is about 9m * 6m * 6m, and the 10-meter method darkroom L * W * H is about 21m * 13m * 9m. The laboratory requires that the parent body of the building is not divided, and there are no beams or columns of the building or structure;

(2) Ground flatness The ground flatness shall not exceed 3 meters and mm, and no accumulated error is allowed. Within the installation range of the darkroom, as the spliced shield plate is the standard size of the factory finished product, there is no accumulated error in the ground flatness that will cause the ground to tilt. If the ground is uneven, it will cause difficulty in assembly and affect the shielding effect;

(3) Provide a dark room independent grounding system with a ground resistance of less than 0. 5 Ω;

(4) The power supply system has no leakage protection device or isolation transformer isolation before being connected to the filter; The power system capacity supply meets the requirements for testing and darkroom power distribution, taking into account the power consumption mode and capacity of the object under test;

(5) The laboratory for testing complete vehicles or parts must consider the method of entering the laboratory for complete vehicles or parts, that is, planning the form of shield doors;

(6) The bearing capacity of the foundation and laboratory ground should be considered to meet the bearing requirements of test equipment and vehicles or parts.


The following issues must be considered during darkroom construction:

(1) The ferrite backing plate needs to be made of environmentally friendly wood panels, as the laboratory environment is closed and non environmentally friendly materials can directly cause environmental pollution;

(2) Determine the installation method of the wave absorbing tip. Improper installation methods can cause unsafe installation or contaminate the test environment;

(3) The surrounding and top of the laboratory are waterproof, and the shielding gasket filled at the direct joint of the shielding material may rust due to water exposure, which can lead to poor shielding effectiveness;

(4) Due to the relatively easy occurrence of problems with the shielding efficiency at the interface board, the interface board in each compartment should choose a conservative interface form as much as possible;

(5) The doors of the darkroom and amplifier room should be connected to the test system to ensure the safety of the test personnel.


3.2. Care should be taken to test the system

Question If you choose the appropriate EMC testing system vendor, generally speaking, there are no issues with the testing system. The only thing to note is that if the key instruments and equipment for the test system are imported from abroad, as domestic regulations require that the imported equipment be remeasured at a domestic metrological institution before use, this part of the cost should be clarified before purchase.


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