This standard describes the test basis, environmental effects, test equipment and environmental parameter measurement of temperature/low pressure/vibration comprehensive test. This standard is applicable to high temperature/low pressure/vibration (sinusoidal) comprehensive test and low temperature/low pressure/vibration (sinusoidal) comprehensive test. GB/T 2424.24-1995 Environmental test guide for electrical and electronic products: temperature (low temperature, high temperature)/low pressure/vibration (sinusoidal) comprehensive test GB/T2424.24-1995 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Environmental testing for electric and electronic products
Basic environmental testing proceduresfor electric and electronic productsGuidance for combined temperature(coldand heat)/low air pressure/vibration(sinusoidal) test
Subject content and scope of application
GB/T 2424.24--- 1995
This standard describes the test basis, environmental effects, test equipment and measurement of environmental parameters for combined temperature/low air pressure/vibration test.
This standard is applicable to combined high temperature/low air pressure/vibration (sinusoidal) test and combined low temperature/low air pressure/vibration (sinusoidal) test. 2 Reference standards
GB/T2424.15 Basic environmental test procedures for electrical and electronic products Temperature/low pressure comprehensive test guide GB2424.22 Basic environmental test procedures for electrical and electronic products Temperature (low temperature, high temperature) and vibration (sinusoidal) comprehensive test guide 3 General description
3.1 The temperature (low temperature, high temperature)/low pressure/vibration (sinusoidal) comprehensive test method is formulated on the basis of GB2423.1 Test A: Low temperature test method, GB2423.2 Test B: High temperature test method, GB2423.10 Test Fc: Vibration (sinusoidal) test method and GB2423.21 Test M: Low pressure test method. Therefore, the relevant basic test principles in GB2424.1 High temperature and low temperature test guide and GB2424.7 Vibration (sinusoidal) test guide are also applicable to this comprehensive test. 3.2 This comprehensive test takes into account the commonly used air pressure range including the ground and aircraft, and the air pressure below 1kPa is not within the scope of this standard. 3.3 Within the considered air pressure range, the surface temperature of the heat dissipation test sample will be greatly reduced under forced air circulation conditions than under "free air" conditions, so the "free air" condition should be used for the heat dissipation test sample. However, considering the additional thermal interference generated by the vibration table and the equipment cannot meet the "free air" condition, it is allowed to use a forced air circulation test method with a wind speed of less than 0.5m/s. 3.4 Under low air pressure conditions, the efficiency of convective heat transfer decreases and the influence of thermal radiation increases. Therefore, the mutual thermal interaction between the heat dissipation test samples in the same test box (room) also increases. In order to avoid thermal interference caused by radiation between heat dissipation test samples, it is best to test only one test sample at a time in this test. Non-heat dissipation test samples and those heat dissipation test samples that are known to have little thermal interference with each other (does not affect the reproducibility of the test) should be tested together with as many test samples as possible. 3.5 The change of material properties caused by temperature will cause the natural frequency of the test sample (such as rubber or plastic device) to drift (i.e. drift to the direction of high frequency at low temperature and drift to the direction of low frequency at high temperature). Therefore, in order to accurately obtain the natural frequency of the test sample, the vibration response inspection should be carried out under comprehensive environmental test conditions. 3.6 The comprehensive test procedure of the test sample is to first carry out sinusoidal vibration and temperature test inspections, and then carry out comprehensive tests. Approved by the State Administration of Technical Supervision on January 27, 1995 632
Implementation on December 1, 1995
4 Environmental effectswwW.bzxz.Net
GB/T2424.24--1995
The temperature (low temperature, high temperature), low pressure and vibration act on the test sample at the same time, which can produce the following comprehensive effects: a. The change of material properties caused by temperature will increase the deformation and cracking of the sealing equipment or seal at low pressure. This phenomenon is aggravated by the superposition of vibration stress, increasing the possibility of leakage. b. Under the simultaneous action of low pressure and temperature, the plasticizers and plastic decomposition products in the engineering plastic parts are volatilized, resulting in changes in the mechanical or electrical properties of the parts. When superimposed with vibration stress, the thermal tendency of deformation and cracking of the parts is increased. c. Other comprehensive effects that cannot be revealed by single or combined tests. 5 Test equipment
The test equipment should comply with the requirements for equipment in GB2423.1, GB2423.2, GB2423.10 and GB2423.21. When developing test equipment by yourself, the configuration of the equipment and the "interface" device should be properly handled. 5.1 Equipment configuration
In general, the vibration table body should be installed outside the test box (room), and only the vibration table surface should be extended into the box (room). This configuration is more reasonable.
If the vibration table is installed in the test box (room), it will not only make the vibration table repeatedly suffer the test of the comprehensive environment and affect the life of the vibration table, but also the heat generated by the vibration table will interfere with the temperature field in the box (room). It must also be noted that the vibration isolation device (such as rubber vibration damper) of the vibration table has a significant change in vibration transmission characteristics under low temperature conditions. At this time, there may be mechanical coupling between the vibration table and the test box (chamber), and the excitation generated by it may damage the structure of the test box (chamber). 5.2 Interface device
When the vibration table body is installed outside the test box (chamber) and the vibration table surface is extended into the test box (chamber), the problem of heat insulation and pressure-resistant sealing interface device between the vibration table and the test box (chamber) must be solved. In addition to meeting the basic requirements of heat insulation and airtightness, the interface device should also avoid mechanical coupling between the vibration table and the test box (chamber) and unfavorable factors such as the vibration table surface deviating from the equilibrium position (rising or deviating from the center) when the air pressure in the test box (chamber) drops.
6 Measurement of environmental parameters
6.1 Temperature measurement
When measuring temperature under the combined environmental conditions of low air pressure and vibration, a temperature sensor with a small mass should be selected and installed firmly so that it does not change the dynamic characteristics at the monitoring point. For heat dissipation test samples, radiation shielding should be used around the temperature sensor to reduce the error caused by the thermal radiation of the test sample.
6.2 Air pressure measurement
Air pressure measurement should usually use a thin and long tube to connect the pressure gauge to the workspace. Because the use of a short and thick connecting tube may cause the sensor element to be heated or cooled by the gas in the test box (chamber) to produce elastic changes and measurement errors. 6.3 Vibration measurement
The vibration sensor and connecting cable must be suitable for the specified test temperature, and they must be calibrated at the test temperature. The sensor should be installed with fasteners. When adhesives are used, the physical properties of the adhesives used must not change at the specified test temperature.
Additional remarks:
GB/T2424.241995
This standard is proposed by the Ministry of Posts and Telecommunications of the People's Republic of China. This standard is under the jurisdiction of the National Technical Committee for Environmental Technology Standardization of Electrical and Electronic Products. This standard is drafted by the Guangdong Post and Telecommunications Science Research Institute. The main drafters of this standard are Chen Jianer, Liang Xiaobing, Han Zhiqiang, Wang Shurong, Wei Bei, 63.1
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