The comprehensive tests specified in this standard are usually used only when a single environmental test on the test sample cannot reveal the comprehensive environmental impact. The test methods specified in this standard are only applicable to test samples that can achieve temperature stability during the test. The test methods specified in this standard can only test one heat dissipation test sample at a time. The heat dissipation test sample should generally be tested in a test chamber without forced air circulation in accordance with the provisions of GB 2423.1. This standard is only applicable to pressure tests with an air pressure greater than 1kPa. For the relationship between altitude, pressure and temperature, see GBl920. The guidance on the comparison of the application of non-heat dissipation test sample tests and heat dissipation test sample tests in GB 2423.1 also applies to this standard. GB/T 2423.25-1992 Basic Environmental Test Procedures for Electrical and Electronic Products Test Z/AM: Low Temperature/Low Pressure Comprehensive Test GB/T2423.25-1992 Standard Download Decompression Password: www.bzxz.net

National Standard of the People's Republic of China
Basic environmental testing procedures for electric and electronic productsTest Z/AM: combined cold/low air pressure testsGB/T2423.25-92
Replaces GB 2423.25--81
This standard adopts the international standard IEC68-2-40 (1976), "Basic Environmental Testing Procedures Part 2 Test Test Z/AM Combined Cold/Low Air Pressure Test" and its 1983 amendment. 1 Subject content and scope of application
1.1 Subject content
This standard specifies the test purpose, test equipment, severity level and test procedures for the combined test of low temperature (temperature gradient and sudden change) and low air pressure of heat dissipation and non-heat dissipation test samples. 1.2 Scope of application
1.2.1 The comprehensive test specified in this standard is usually used only when the test sample cannot reveal the combined environmental impact by a single environmental test. 1.2.2 The test methods specified in this standard are only applicable to test samples that can achieve temperature stability during the test. 1.2.3 The test methods specified in this standard can only test one heat dissipation test sample at a time. The heat dissipation test sample should generally be tested in a test chamber without forced air circulation in accordance with the provisions of GB2423.1. 1.2.4 This standard is only applicable to pressure tests with air pressure greater than 1kPa. 1.2.5 For the relationship between altitude, pressure and temperature, see GB1920. 1.2.6 The guidance on the comparative application of non-heat dissipation test sample testing and heat dissipation test sample testing in GB2423.1 also applies to this standard. Note: The definition of non-heat dissipation test samples is as specified in GB2422, and the temperature of its hottest point should not be measured under low air pressure. 2 Reference standards
GB1920 "Standard atmosphere (below 30 km)" GB2421 General rules for basic environmental testing procedures for electric and electronic products GB2422 Terminology of basic environmental testing procedures for electric and electronic products GB2423.1 Basic environmental testing procedures for electric and electronic products Test A: Low temperature test method GB2423.21 Basic environmental testing procedures for electric and electronic products Test M: Low pressure test method GB2423.22 Basic environmental testing procedures for electric and electronic products Test N: Temperature change test method GB2424.1 Basic environmental test procedures for electric and electronic products Guidelines for high and low temperature tests GB2424.15 Basic environmental test procedures for electric and electronic products Guidelines for temperature/low pressure comprehensive tests 3 Test purpose and general description
3.1 Test purpose
The purpose of this test is to determine the adaptability of components, equipment and other products to the low temperature-low pressure comprehensive environment to which they are used and (or) stored Approved by the State Administration of Technical Supervision on July 1, 1992 and implemented on March 1, 1993
GB/T2423.25-92
3.2 General description
3.2.1 This test is a combination of GB2423.1 Test Ab or Ad and GB2423.21 Test M. 3.2.2 In the test, the test sample shall first be subjected to a low temperature test of the severity level specified in the relevant standards. If the test sample is to work during the test, it must be tested to ensure that the test sample can work normally. Then, while the temperature is maintained at the specified value, the pressure of the test chamber is reduced to the test pressure specified in the relevant standards. This temperature and pressure condition is maintained for the specified time. Figures 1 and 2 show the cross-section of this procedure.
Clause or sub-clause
Test room temperature
Specified test temperaturebZxz.net
Test room air
Specified test air pressure
3. Power on the test sample
4. Functional test and
(or) appearance inspection
Initial test,
·Intermediate test
8. 2.5,8.2.618.2.7
Conditional test
Test sample temperature
Test chamber temperature
Test chamber pressure
Exposure time
Test sample can be powered off
Figure 1 Test profile of non-heat dissipation test sample18.2.8
Final test
Clause or subclause
.Temperature
Test chamber temperature| |tt||Specified test temperature
Test room air pressure
Specified test air pressure
3.Power on the test sample
[4.Functional test and
(or) appearance inspection
4 Test equipment
4.1 Test chamber
Initial test
*Intermediate test
GB/T2423.25-92
X.2.5, 8.2.6, 8.2.7
Conditional test
Test sample temperature
Test chamber temperature
Test chamber pressure
Fin time
Relevant standards may require that the test sample be de-energizedA
Figure 2 Test surface diagram of heat dissipation test sample
Final inspection
4.1.1 The test chamber shall be able to produce and maintain the test conditions specified in GB2423.1 Test Ab or Test Ad and GB2423.21 Test M. However, the temperature requirements for the chamber walls do not apply during temperature and pressure changes. 4.1.2 When restoring pressure, the auxiliary equipment, devices and introduced air of the test chamber should be prevented from contaminating the air in the test chamber. 4.2 Installation
When the heat dissipation test sample is tested, its installation shall comply with the requirements specified in GB2423.1 Test Ad. 5 Severity Level
5.1 General Requirements
5.1.1 Severity is expressed in terms of temperature, air pressure and exposure duration. The severity level selected for the test shall be specified in the relevant standards. 5.1.2 Temperature, low air pressure values ​​and their tolerances and durations - shall generally comply with the provisions of GB2423.1 Test Ab or Test Ad and GB2423.21 Test M.
Note that when the air pressure is lower than 10 kPa, it is difficult to achieve the temperature tolerance requirements specified in Test A. In this case, the relevant standards may specify a larger tolerance. 5.1.3 The exposure duration shall be calculated from the time when the test sample reaches temperature stability under low air pressure conditions (see Figures 1 and 2). 5.2 Priority of temperature, air pressure and duration. A set of temperature, air pressure and duration values ​​shall be selected from the following table in priority. 273
6 Pretreatment
GB/T 2423.25-92
Corresponding height
Relevant standards may require pretreatment and specify the pretreatment atmospheric conditions and time. 7 Initial inspection
The test samples shall be subjected to visual inspection and electrical and mechanical performance inspection in accordance with the relevant standards. 8 Conditioning test
8.1 General provisions
8.1.1 Heat dissipation test samples
Duration
The test shall be conducted in a test chamber without forced air circulation in accordance with the provisions of GB2423.1 Test Ad. If the test chamber used for the test is large enough to meet the conditions specified in GB2423.1 Test Ad, the test may be conducted using Method A of GB2423.1 Test Ad.
8.1.2 Non-heat dissipation test samples
Can be tested in a test chamber with or without forced air circulation. 8.2 Test procedures for heat dissipation test samples without artificial cooling and non-heat dissipation test samples 8.2.1 Place the test samples in their normal working position or in accordance with the relevant standards in the unpackaged, unpowered and ready-to-use state into the test chamber. At this time, the temperature of the test samples and the test chamber is the ambient temperature of the test room. 8.2.2 Adjust the temperature in the test chamber to the specified test temperature at a rate not exceeding 1°C/min (not greater than the average value of 5min), and allow the test samples to reach temperature stability at this temperature. The test temperature should be measured in accordance with Article 2.7 of GB2422. Note: The maximum change rate of 1C/min is not applicable to test samples that can withstand thermal shock, such as test samples that can usually withstand the rapid changes specified in Test Na or Test Nc in GB2423.22. 8.2.3 This clause is only applicable to test samples that are required to work during the test. Power on the test sample and test it to see if it can work according to the requirements of the relevant standards. Then turn off the power and allow the test sample to reach temperature stability.
Related standards may specify other test procedures for low temperature and normal pressure. 8.2.4 Reduce the pressure in the test chamber to the specified test value at a rate not exceeding 10 kPa/min. 8.2.5 This clause is only applicable to test samples that are required to work during the test. Power on the test sample or apply an electrical load to see if it can work according to the requirements of the relevant standards. Then, keep the test sample in working state or disconnect the power supply according to the relevant standards. If the relevant standards have requirements, intermediate testing can be carried out according to Article 9 of this standard. 8.2.6 Maintain this temperature and pressure condition for the specified time. 8.2.7 This clause is only applicable to test samples that are required to work during the test. 271
GB/T 2423.25-92
During the last 1h of the low pressure time, perform intermediate testing according to the requirements of the relevant standards, and then cut off the power supply or remove the load. 8.2.8 Restore the pressure in the test chamber to normal pressure at a rate not exceeding 10kPa/min, and at the same time, slowly increase the temperature of the test chamber to the temperature range of the standard atmospheric conditions of the test room at a rate not exceeding 1C/min (not greater than the average value of 5min). Note: The maximum rate of change of 1 °C/min does not apply to test specimens that can withstand thermal shock, for example, test specimens that can normally withstand the rapid temperature changes specified in Test Na or Nc.
8.2.9 The test specimens are recovered in the test chamber or in accordance with the relevant standards. 8.3 Precautions when testing test specimens with artificial cooling. See GB2423.1 Test Ad9.7.2.
9 Intermediate test
See GB2423.1 Test Ab and Ad.
10 Recovery
See GB2423.1 Test Ab and Ad.
11 Final test
Perform visual inspection and electrical and mechanical performance tests on the test specimens in accordance with the relevant standards. 12 Information to be given in relevant standards
When applying this test method, the following applicable details should be given in relevant standards: a.
Pretreatment;
Initial test;
Detailed requirements for mounting frames or supports (applicable to heat dissipation test samples), test sample status (including cooling system), severity level (temperature, pressure and exposure duration), whether the temperature change is sudden or gradual; test items to be carried out at low temperature before depressurization, inspection, measurement and loading requirements during low temperature/low pressure test; load conditions during recovery;
Final test.
Additional notes:
This standard was proposed and coordinated by the National Technical Committee for Environmental Conditions and Environmental Testing of Electrical and Electronic Products. This standard was drafted by the 301st Institute and the 601st Institute of the Ministry of Aerospace Industry. The main drafters of this standard are Xia Yuemei, Zhu Yaochang and Zhang Leshan. 275
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