3m semi-anechoic chamber construction and EMI testing technology practice
EMI / EMC design of electronic product design engineer m Cheats essential manual download EMI-test.rar
Abstract: This paper describes the construction of 3-meter semi-anechoic chamber EMI should pay attention to the actual test questions and test result analysis techniques, and special.
Keywords: EMC anechoic chamber testing technology
EMI EMC (EMC) is the last ten years developed a new discipline. With the importance of people's knowledge of its continuous improvement of many countries and regions have made it compulsory certification management. such as the United States in accordance with the FCC (Federal Communications Commission) regulations, the European Community in accordance with the 89/336/EEC Electromagnetic Compatible EMC certification instructions, not in accordance with these regulations and directives for electromagnetic compatibility certification and the certification does not allow unqualified products in these countries and regions on the market and use. China State Administration of Quality and Technical Supervision also in October 1999 EMC certification issued a management approach that contains the [1999] Document 223. In order to meet the EMC certification of the implementation of management practices, some testing agencies and production companies have introduced the EMC EMC test equipment and built a semi-anechoic chamber test There are many inspection agencies and manufacturers in this regard the ongoing construction and building plans to invest in this area.
I center in October 1999 built its own development of Tai Chi Villa open test field emission of electromagnetic radiation; from abroad advanced EMC test equipment; EMC testing of the new 3-meter semi-anechoic chamber is also in March 2000 and put into use. in 3-meter semi-anechoic chamber construction and EMI (electromagnetic interference) testing, accumulation and summarizes some experience, for your reference and reference. The following were from the semi-anechoic chamber 3m construction and information technology equipment, the two aspects of EMI testing techniques described.
a .3-meter semi-anechoic chamber construction < br> (a) 3-meter semi-anechoic chamber
building aspects involved in the construction when the chamber in general, will involve the following aspects:
1. anechoic chamber size. you should be aware that you have to build The chamber is a standard 10-meter semi-anechoic chamber or a standard 3-meter semi-anechoic chamber site, or be customized according to your size anechoic chamber; anechoic chamber is to support the construction of a shielded control room and amplifier room, their respective long, width, height and size is the number, which they built in a dark direction.
2. PSD of the type, size and quantity. PSD sub-pole, pole, Mito, such as different types, and with electric, pneumatic and manual three. you want a future based on your test equipment and personnel out of convenience and the PSD of the shielding performance, durability, reliability, easy maintenance and other aspects into account to select them.
3. shield plate type and connection. As the manufacturer of the chamber used to build different types of dark shielding plate, the connection between the shield and technology is not the same. In order to ensure close contact and good electrical continuity, should pay attention to their choice shielding plate and the connection between the shield plate to understand and compare.
4. shielded room shielding. darkroom manufacturers should be allowed to provide electromagnetic shielding of the shielding can be achieved specific performance indicators (give a specific value) , which should include different frequencies (from low frequency to high frequency) of the magnetic field, electric field, plane wave, microwave shielding performance.
5. absorbing materials. Notice chamber used by manufacturers manufacturers absorbing materials and models (including the ferrite absorbing materials and wedge absorbers); attention to absorbing material of the structure and its resistance to high temperature, high humidity and fire retarding properties; understand the long-term use is easy to deform and a variety of suction material in different wave bands of the absorbing performance, understand their way in the dark room and laying the laying position and role.
6. the power line and signal line filters. consider the good dark type of power to be used in future and their maximum power, such as test equipment, tested equipment and auxiliary equipment and lighting systems, whether to use 380V, 220V, 110V AC voltage, the need for testing and tested DC power supply equipment, the numbers are, whether there are special test equipment and auxiliary equipment require special filters, all of which need to be considered thoroughly, so that these suppliers are ready ahead of the power line and signal line filters.
7. letter guide and waveguide hopper windows. dark room needs to be installed Bird ventilation window and the exhaust fan or air conditioning system connection. Note the band waveguide hopper windows designed to comply with its shielding shielding shielding room. letter guides to install shielding wall can not be installed directly through the terminal or the signal interface ; letter installation guide number, location and its terminal on the number and type, and test equipment suppliers to discuss together to decide.
8. fire alarms and lighting facilities. Note that the choice will not have any radio interference lighting facilities; fire alarm installation should not affect the chamber performance.
9. dark room automation devices. dark room automation equipment including the antenna down the tower, turntable and the monitoring system and can control them controller. antenna down the tower to be considered the choice of manufacturer, model and whether to install the antenna adapter, if supported by the test equipment (ie, its test equipment connected to the test whether the software drivers that support it); turntable should also be supported by the test equipment and in accordance with the size of the EUT to determine the size and carrying capacity turntable, taking into account the rotation of turntable angle and positioning accuracy; control system includes a camera installed in the darkroom and placed in the control room Monitor, according to the actual use to select the number of cameras and monitors, cameras to choose in a wide frequency range and high-intensity work the field and does not generate radio frequency interference signal models, and its shooting area installed in the absence of food.
10. anechoic chamber performance testing and warranty training. applies not only to the chamber in EMI EMC testing can also be used for EMS in radiated immunity testing. Therefore, the chamber's performance testing to including the chamber after the completion of the shield and the chamber shielding performance tests after the completion of all construction site attenuation testing and field uniformity test. these tests according to the contract requirements and the construction of the international acceptance of chamber to carry out the relevant standards. To select a profile and after authority recognized testing agencies. darkroom warranty and support equipment, parts warranty, and training and going to be written into the contract.
(b) information technology equipment for testing the function of chamber
need to increase the information type of equipment under test needs, needs in the general darkroom on the basis of the functional type of equipment to add some information on the private interface. These interfaces include: the standard monitor port, parallel printer port, RS232 serial communication interface, USB Interface, PS / 2 interface, video and audio interfaces , IEEE488 parallel interface. the addition of these interfaces, since separate interface device for these tests is very easy to distinguish between the disturbance source and the isolation and analysis of the impact of other devices to provide a good way.
manufacturers of the chamber construction Information processing equipment testing different interface. I Center 3-meter anechoic chamber to provide a construction company adopted a turntable from the control room to the chamber method of shielding the channel. Its function is implemented as follows: all the above interface cable penetration shielding the channel, the interface line interface on both ends to install the plug or socket, a dark room in the device under test and connected to an auxiliary control room connected with the devices. shielded channel ports in the control room full of copper / iron silk floss to prevent possible into the chamber of the electromagnetic interference. If the interface connection has shielded the skin, shielding the skin can be connected to the port ground terminal on the shield, thus completely avoiding the interference of the chamber. This may be brought into the conducted interference is very weak, not enough affect the test results. when such testing is not required, you can control room this side of the interface cable into the mask channel, shielding Channel ports can be used with the lid. It is also possible changes for the future and the interface can be extended of providing the convenience and flexibility.
other construction companies to take a dark room known as the -2mm size of the copper particles (RFI Trap shielded cable as an multiterminal sleeve). In this way, copper particles formed inside a bare metal RF shielding cable shield contact. Trap can use many cable without the cable cut through, like many of the cable through a coaxial cable. cable outer shield must be stripped, making the shielded cable is part of the package exposed. RFI Trap can be poured and clear empty. RFI Trap can be installed in the shield plate can also be removed with a shutter-like interface board replaced its position.
(c) of the chamber construction process should pay attention to the problem
chamber is a large construction project to spend a large sum of funds, many technical details to consider, a little ill-will bring human, financial and material losses on the work of the future left many troubles. According to the Center 3-meter semi-anechoic chamber construction experience in the following aspects need attention:
1. technical bid comparison
contract before the chamber to find a few construction companies, for their careful comparison of technical bids, respectively the content of their tenders for technical discussion and careful inquiry, the details of the bids, the more clearly understand better.
2. to understand the strength of
chamber construction companies construction companies to understand the background of dark and technical strength, so that They provide domestic and overseas examples of chamber construction, the best they can be built similar to the darkroom to the field visits.
3. and test equipment manufacturers to provide coordination and cooperation
used in future test chamber equipment manufacturers to determine, preferably after the signing of a construction contract darkroom. Because the test equipment and darkroom equipment there are many links where necessary, test equipment related to cable length and placement of auxiliary equipment, the signal lead connection terminal board and the number and type of chamber design so closely related. Therefore, we must find the construction process chamber test equipment manufacturers together to discuss and determine the connection details related technologies, and coordinate the relationship between them, define their respective responsibilities.
4. construction workers
site construction experience and quality of the experience and quality of staff is also very important to the construction of high-quality trained staff is an important guarantee for darkroom built. In every stage of the construction process, we should pay more attention to View the shield close connection and electrical connection connectivity, pay attention to see filters, shielding channel and credit tightness of the screw guide, which will affect the after dark screen shielding the cavity built good or bad. ferrite paste watt-hour is taken to keep the body cavity temperature shielding, ferrite tile attention to check with the adhesive paste is sufficient and uniform brush to prevent future cavities ferrite tile detached from the shield, causing personal injury.
5. fireproof, waterproof and safe handling measures
darkroom darkroom construction site and installation of the insulation layer. so be sure to pay attention to water, or insulating layer will be destroyed. while also dealing with fire prevention. for the prevention of outside hedge against in the first place, preferably in consultation with the chamber works, in the darkroom ceiling pull a safety net to prevent the ferrite tile fell, hurt staff and facilities.
6. The final acceptance of completed construction work
darkroom, urge the chamber to pay attention to manufacturers and test equipment manufacturers with complete test equipment and darkroom equipment, installation and commissioning work, so that the whole system to work properly. to background noise testing to meet the contract requirements. related to the darkroom darkroom equipment manufacturers ask for Manual and related equipment, installation of electrical outlets and other layout (because most of them are installed under the raised floor) as the basis for the future to find and repair. darkroom should also allow manufacturers to leave more vulnerable parts, so that they provide repair services fast enough to respond.
II. information technology equipment EMI testing technology practices of information technology equipment
EMI (electromagnetic interference) test consists of two aspects: the radiated and conducted emission testing. radiated emission is spread in space The conduction disturbance to the public through the power line transmission grid. our current information technology equipment Radio disturbance test standard is GB9254-1998, equivalent to the standard of international standards CISPR 22, the same as with the European standard EN 55022.
I center in 3 m semi-anechoic chamber method for the EMI test system in Germany Rohde & Schwarz (R / S) products, one of the important receiver models with full compatibility testing is the ESI 26. The range of frequency measurement receiver from 20Hz to 26.5GHz, is included with the receiver, computer, spectrum analyzer functions in one of three types of aircraft. Rohde & Schwarz is the world's largest-known radio interference test receiver manufacturers, the EMC test equipment has extensive experience in manufacturing. test system software is the soul of the system, provided by Rohde & Schwarz test receiver with the ESI 26 supporting the preparation of test software ES-K1 very successful. The test system software provided for the EMI test on the basis of a fully automated solution with the composition of each module as a whole and their mutual independence, degree of automation and flexibility in applications are very high, the user interface is also very well written, easy to use and also very intuitive, very comfortable .
the past year, through the use of ESI 26 test system on a large number of micro-computers and other information technology equipment for testing and on the ES-K1 software trial and error, practice, summed up the experience of some tests, the common line as a reference and common study.
(a) with ES-K1 software automatic testing of several important steps in the use of ESI 26
test system software ES-K1 fully automated radiation emission test, to note several important steps: first make sure the system control computer on the ESI 26 receiver, turntable, antenna tower control normal movements, and then test the demand for ES-K1 program Navigate File menu item including items under the various sub-parameters are set correctly; its child parameters entry in the (data reduction) parameters that affect the test results and test the accuracy of the important parameters of the length of time items should be properly prepared according to test requirements; another one is under Navigate into the on the DataReduction setup and test time and test results are closely related, only a deep understanding of its meaning for each project and make the correct settings, will get a multiplier effect. Here I do not start to talk, just the actual number of radiated emission test examples are explained. Figure 1, Figure 2 is a restrictions limit the data deviate from the judge as qualified curves in Figure 1, Figure 2 and the grid does not curve, one can be judged. Figure 3, Figure 4 is in the Since the device under test (computer system) produced the type of harassment vary widely, from Figure 3, Figure 4 test curve can be seen, although the ES-K1 test software automated test results are given (some quasi-peak value) is qualified, but many peaks is excessive, and many exceeded the peak no quasi-peak test, this case can not be jumping to conclusions, need to re-set entry value from The 30MHz ~ 1GHz, into 30MHz ~ 40MHz (Fig. 4 cases) or 300MHz ~ 1GHz (Figure 3 cases), it will be difficult to determine the frequency band to do a more refined range of more detailed re-measurement; if necessary can not be determined frequency of harassment manual measurements to determine the final consolidated.
(c) Note that the maximum emission
find the device under test during the EMI radiated emission testing, should be noted that the system under test to find the maximum emission. If the computer system being tested, the components of the system should support the display's brightness and contrast to maximum, but also to change the display resolution and refresh rates were tested. For the external interface of the computer such as the COM port and parallel printer port, etc. to be connected to the MODEM and printers with the composition of the tested system; to run a dedicated EMI testing procedures, in the Black Lands on the display of full screen white unstable frequency, ES-K1 test software with a single point test function, the amplitude of the fluctuations in the frequency of harassment, arbitrary point of repeated tests, and automatically maintain the maximum amplitude. Here we must note that the computer with the measured composition MODEM test system and printer to choose low radiation emission, and to test screening, and their harassment of the best value is less than the standard limit to be limited to 6dB.
(d) EUT placed
EUT (equipment under test) and static placement of auxiliary equipment, GB9254-1998 standard in detail in the illustrations and instructions to make them generally positive to the outer boundary of the location of the antenna is 3 meters. But after the turntable turn up For the receiving antenna system under test will change the distance; for this change, there is no standard description of the field, test equipment, which is often raised doubts inspection side. we passed the actual test, it was found that small differences in distance little effect on test results received, the device under test on the antenna azimuth greater impact on test results.
(e) the background noise and test software code changes to the Center chamber
30MHz ~ 1GHz background noise ratio GB9254-1998 B-level limit lower limit of 20dB, but if the automatic test, you incorrectly modify the increased 10dB, so pay attention to correctly set the content. In addition, ES-K1 software requirements for the test program set a password, the password into the operator password and administrator password. does not allow the operator to change system settings, can only be tested The system administrator can change the test system settings can also be tested. so pay attention to management at different levels, once the test system is set up, it should not be changed. passwords to remember, in case the password forgotten, will not enter the test system. Here are Forgot your password after the removal of the original password, password reset method:
editing software ES-K1 EXECUTE subdirectory under the installation directory under the ES-K1.INI file, perform the following steps:
1. will file to the user name . Exit ES-K1 test software, re-enter the ES-K1.INI file;
6. the INI files, re-entering the ES-K1 test the software, you can reset your password.
III. Conclusion
short, 3-meter semi-anechoic chamber and EMC testing EMI testing technology is a very important part, which is interdependent and interrelated. high standards of quality test environment (3-meter anechoic chamber) and inspection staff a wealth of experience in EMI testing, EMC testing to improve the quality of the important factors. These are some of my personal experience and understanding, and more details still need to practice in the future continue to recognize, explore and summarize the hope that the contents of the text can be helpful to everyone.
EMC m must break the technical barriers
EMI / EMC Design Cheats m electronic product design engineers will Preparation Manual EMI-test.rar
a conducted interference to make 70% of the domestic PC into the ranks of substandard products, and conducted interference of electromagnetic compatibility of electronic products is an indicator. electromagnetic compatibility has become a restricting China's exports of electronic products a technical barrier.
mm Zeng electromagnetic conductivity 70% of SMEs in the quality of the Lok Ma
back in September 1996, the State Bureau of Technical Supervision in conjunction with the former Ministry of Electronics Industry of the domestic computer had a sample of the product quality inspection, the results can not be optimistic, PC's pass rate was 61.5%. 27 projects in 7 categories comprehensive examination, conducted interference failed to become the most prominent problem.
conducted interference is electromagnetic compatibility testing of electronic products a project of this spot check 70% of businesses failed the problem here, and electromagnetic compatibility indicator is the mandatory requirements of national standards. Therefore, only this one failed to be designated as substandard products, there is no discussion room.
that 70% of the enterprises, When products in the electricity grid will be issued on the interference signal, if the interference signal is too large, it will affect the quality of the electricity grid, thereby interfering with the normal operation of other appliances. Therefore, most countries conducted interference of electronic products, indicators a rigid provision prohibiting the conduction disturbance is too large production and sales.
mm electromagnetic interference against the growing problem of electromagnetic compatibility
a matter of fact, conducted interference is a fundamental problem of electromagnetic interference, which is due to PC caused by power failure, compatible manufacturers generally use cheap power supply, coupled with a filter as long as we can guarantee the transmission interference detection coil clearance. So what is it EMI?
EMI (Electromagnetic Interference-EMI) is an electronic equipment or system or external energy emitted stray into the electronic device or system, spurious energy, such as between the laptop and test equipment, printers and desktop computers as well as between cell phones and medical equipment so high between the frequency electromagnetic interference. electromagnetic interference, including conduction (low frequency) EMI, radiation type (high frequency) EMI, electrostatic discharge (ESD) or lightning caused by EMI.
entered the information in human society today, the electromagnetic waves as a resource 0Hz ~ 400GHz bandwidth in the range, widely used in information technology products, such as automotive, communications, computers, home appliances, large numbers of human society and the Chung family. it brings a low-frequency electromagnetic interference from the microwave will band, all-pervasive to radiation or conduction to the operation of the sub-device or system and the surrounding environment, to the equipment or system brings even more serious ecological damage.
information technology equipment electromagnetic interference can not be ignored. the computer has towards high speed, high sensitivity, high integration and multifunction, the system is in many sub-systems contain a variety of low-voltage components and the complexity of devices to transmit information. High-speed and high-density system, the radiation will increase, low, high sensitivity would the system's immunity. As a result, the electromagnetic environment of mutual interference and harassed within the system, a serious threat to the work of computer and digital system stability, reliability and security.
in the family, commercial, plant and transport level in the microprocessor is constantly increasing. In the future, in a variety of electronic equipment room will have more launch and sensitive equipment, the corresponding problems will follow.
Now, with the Bluetooth technologies, in almost all electronic devices can occur in the new launcher. Bluetooth is a use of 2.4GHz ISM (industrial, scientific and medical equipment) band, roughly in the range of electronic devices within 30m Automatic frequency hopping wireless communication specifications. more than 1,200 worldwide, the company has accepted the operation of the Bluetooth specification. By 2004, there will be 400 million devices using Bluetooth. Clearly, the incident radio signal when exposed to the next, the use of Bluetooth devices should work. but we are not able to determine that the design close to other non-Bluetooth devices can work without interference.
electromagnetic leakage of information technology equipment, information security threat. In the Internet age Information leakage is considered the greatest threat to network security. However, the computer's keyboard, screen and so will the information through the radiation leak out. This is called TEMPEST phenomenon. a more precise definition is an electronic information device through the electromagnetic energy emission leakage of information generated.
United States has been done in New York test, the radiation signal interception device Customs House, Federal Reserve Bank, the World Trade Center, City Hall, police headquarters, the telephone office and the United Nations Headquarters in New York and other units are working on a computer monitor radiation signal. The results surprised to find that New York is a huge information base. < br> EMI hazardous to your health. Today, many medical devices using advanced electronics and information technology. immunity of these devices is directly related to the safety of people's lives. such as the heart device from the shoulder, often would be from computers, mobile phones and other electromagnetic interference, its function changes. It is said that a pair of artificial limbs controlled by the bio-electrical, electromagnetic interference in high-voltage lines by the descendants of Yang under the car turn. This is the electromagnetic interference of medical equipment through the interference of indirect damage caused by the human body.
the rapid development of EMC mm edge discipline
IEC under electromagnetic compatibility are defined as: to complete its function, without creating unacceptable interference. areas, such as microwave technology, microelectronics, computer technology, communications and network technology and new materials. electromagnetic compatibility of a wide range of technologies, involving almost all modern industries.
including equipment within the electromagnetic compatibility of circuit module compatibility between the equipment and the compatibility between the systems compatibility. interference between the circuit performance degradation is one of the main equipment. digital device with the pulse current and voltage is very rich in high-frequency harmonics, and therefore have a very strong radiation. in fact universal digital circuits, the electromagnetic interference problem was becoming increasingly prominent. interference between devices, mainly through two ways: one is the space in the form of electromagnetic interference; the other is through the power line interference, so the power output device to be installed at the entrance to the general power line filter.
electromagnetic compatibility of the three elements: electromagnetic interference, coupling means, sensitive equipment. to solve this problem of electromagnetic compatibility 3 two-pronged approach to eliminate one of them. In order to achieve electromagnetic compatibility must examine the following five issues: in-depth study of electromagnetic interference source, including its frequency and time domain characteristics, resulting in the inhibition mechanism and measures; in-depth study propagation characteristics of electromagnetic disturbance ;-depth study of the ability of sensitive equipment immunity;-depth study of methods of measurement of electromagnetic compatibility;-depth study of the system and the electromagnetic compatibility between systems.
electromagnetic compatibility testing of engineering methods to modify laws, in the design process electromagnetic compatibility as far as design, prototype testing is completed, if found not to meet the electromagnetic compatibility requirements, and then be modified to meet the requirements until the date, the method is suitable for relatively simple device, but development costs are high; system design, In the product design process to carefully predict the possible occurrence of electromagnetic compatibility problems, beginning from the design to take various measures to avoid the problem of electromagnetic compatibility, this method can usually be resolved before completion of the formal product 80% of the electromagnetic compatibility problems.
EMCmm domestic electronic equipment must break through technical barriers
20 a century since the 90s, many countries have enacted laws, management practices and standards, and electrical and electronic equipment production and market distribution, as well as in the activities of electromagnetic radiation stations and the establishment of enterprises, the implementation of the overall management and supervision, in particular, is widely carried out EMC certification system to ensure public safety and public interest.
With the development of market economy, China should participate in the world technology market competition, import and export of electronic products must pass EMC tests. Therefore, our government and relevant departments increasingly concerned about EMC issues, and constantly develop the relevant mandatory standards. the various departments and the military also began to study and the establishment of EMC laboratories of different sizes and testing centers.
but must face the fact that the electromagnetic compatibility of electronic products, compared with developed countries also have a big gap. attaches great importance to the international EMC of electronic products design, and electronic products in many countries of the electromagnetic compatibility standards are enforced, so EMC has become a restricting exports of electronic products in China, a technical barrier.