Electromagnetic compatibility testing is usually divided into three levels: equipment and
LM2594HVM-12 datasheet and subsystem electromagnetic compatibility test, the system electromagnetic compatibility testing and
LM2594HVM-12 price and system electromagnetic compatibility test environment (also called inter-system electromagnetic compatibility test). Usually the system electromagnetic compatibility
electromagnetic compatibility testing and
LM2594HVM-12 suppliers and environmental testing systems collectively referred to as system-level electromagnetic compatibility test.
This chapter includes system-level electromagnetic compatibility test on the basic concepts, the need for electromagnetic compatibility and complexity of system level EMC test requirements, test the content and implementation of some note.
1, the basic concept
(1) performance threshold performance thresholds used to describe the performance characteristics of a technology EUT or failure to achieve the limits, in theory, is a specific constant, and In fact performance threshold is usually a data area. Above the upper limit of this region, the measured system can work; below the lower limit in this region, the state of the system under test as unacceptable. Upper and lower middle area is a gradual transition zone, called the critical area. For a specific test system, the performance threshold expression should be clear, making the system electromagnetic compatibility test, you should indicate in the technical documentation of the system under test which of the indicators for the system electromagnetic compatibility test on performance criteria.
(2) the key point for a complex electronic system, often the most sensitive to interference as a key click, with sensitivity, the inherent sensitivity, the importance of the mission objectives, and in which the electromagnetic environmental factors, is actually an electrical point. For example, in the receiver to choose their RF input, IF input, IF output, input or output detector for determining the baseline performance thresholds.
(3) monitoring point monitoring points in the system electromagnetic compatibility test used to monitor the response of the system in one or more actual physical location, it can be installed within the system, also available at the output. But it is important to ensure that monitoring equipment installed on the monitoring
not affect the test results.
(4) radiation emission limits radiation emission limits is given in the task book, the system under test and the amplitude of the radiated emission limits of spectrum, which is based on theoretical analysis and practical experience that a system to allow radiation emission, which is to provide the design limit. It is a function of frequency.
(5) limits the radiation sensitivity radiation sensitivity limit is given in the task book, the system under test and the amplitude spectrum of radiation sensitivity limit, which is based on theoretical analysis and practical experience, that a system should be able to tolerate outside interference value, which is the system resistance to interference of a radiation design requirements. It is a function of frequency.
(6) radiated emission radiated emission test value test value is useful to test the system and do not want to launch some of the measured value. It can not be a constant, and testing frequency and test location-related.
(7) the radiation sensitivity radiation sensitivity threshold threshold is measured after the system receives analog interference showed the smallest discernible, and some do not want to respond in case of interference signal level, but also said sensitivity threshold. It is a function of frequency, usually measured by. As the sensitivity threshold of the test more time-consuming, laborious, engineering generally interested only in certain frequency point on. In practice, when the system under test measured on a frequency electromagnetic interference (defined as where
at the receiving device) is less than the receiving device associated with the sensitivity limits, and there is a certain margin (eg 3 ~ 6dB), then the measured threshold sensitivity of the system
quantitative test can be done free. The sensitivity threshold of the actual system is not only related by the probability of electromagnetic interference, but also with other factors related, not a simple or pure electromagnetic parameters of the data, engineering analysis of specific issues have been guided by the principle of discretion.
(8) safety factor safety factor of electromagnetic interference as defined in the GJB 72-85 "electromagnetic interference and electromagnetic compatibility terminology" sensitivity threshold expressed as a critical test points and appear in the line or signal interference ratio. In GB/T4365---1995 "the term electromagnetic compatibility", the margin with a design value of emission and immunity margin designed to characterize the electromagnetic compatibility index value (theoretical value).
theory to the sensitivity limits and emission limits as the difference between the safety factor. Launch margin refers to the device, equipment or system level electromagnetic compatibility and the difference between the emission limits. Electromagnetic compatibility level is the expected increase in the working conditions of the specified device,
equipment or system specified maximum electromagnetic disturbance level. Emission limit is specified maximum electromagnetic disturbance source emission level. Immunity margin (margin sensitivity can also be said) is a device, equipment or system immunity limit (sensitivity limit can also be said) and electromagnetic compatibility level of the difference between. Immunity is the specified minimum limit immunity level. Different frequencies of radiation emission test on the product is lower than the rate of radiation emission limits is not the same, this difference is called the launch margin test value is a function of frequency.
measured on the products of different frequencies of radiation sensitivity threshold is higher than the sensitivity limits of the different levels of radiation, said the difference for the sensitivity margin test value, which is a function of frequency. Used in engineering to electromagnetic interference test value and the measured emission sensitive
understand the difference between the threshold measured for the system safety factor, which is used to describe a complete system level EMC.
power stone block interference because the randomness of the system work more complicated. During the test of time, location, environmental conditions, the system on-line working, not enough to express the system electromagnetic compatibility. In order to protect the reliability of the system can impose harsh conditions of acceptance
moment. Specific operation, you can increase the systems power transmission equipment (an additional transmitter margin), or to test the system more sensitive receiving equipment to work (to increase the sensitivity of a margin). Commonly used in practical engineering systems most vulnerable obtained through analysis of disturbing frequency transceiver pair, the value for their jammer and receiver sensitivity tests to estimate the safety factor.
system receiving equipment and key safety factor sensitivity, inherent electromagnetic sensitivity, mission objectives and the importance of the electromagnetic environment in which other factors, can-type (2.15), said.
when 777, dB 10, the said system is in critical condition. When mdB> 0, it is called self-compatible system, safe and reliable. Often the actual system into the system safety factor safety factor of the receiver, the transmitter safety factor, safety factor parasitic interference.
(9) classification system, equipped with highly critical equipment interference, the system will cause potential performance degradation. According to different levels of performance degradation can be divided into three categories:
a class is a serious hazard or reduce the life span;
II refers to the ability to perform tasks the system down;
three refers to the system of non-essential functions damage.