The high and low temperature test chamber is a commonly used experimental equipment, suitable for reliability testing of industrial products at high and low temperatures. It is widely used in fields such as automobiles, motorcycles, aerospace, marine weapons, and scientific research institutions. How should users choose high and low temperature test chamber products? Below, the editor will provide a specific guide for selecting high and low temperature test chambers, hoping to help users better apply their products.
1. Reproducibility of environmental conditions
It is impossible to fully reproduce the environmental conditions that exist in nature in the laboratory. However, within a certain tolerance range, people can accurately and approximately simulate the external environmental conditions that engineering products undergo during use, storage, transportation, and other processes. This statement can be summarized in the language of engineering, which means that "the environmental conditions (including platform environment) created by the testing equipment around the tested product should meet the requirements of the environmental conditions and their tolerances specified in the product testing specifications. The temperature chamber used for military product testing should not only meet the high and low temperature test values and test times specified for different types of products in the national military standards GJB150.3-86 and GJB150.4-86, but also meet the requirements for temperature field uniformity and temperature control accuracy in the test specifications. Only in this way can the reproducibility of environmental conditions be ensured in environmental testing.
2. Repeatability of environmental conditions
An environmental testing equipment may be used for multiple tests of the same type of product, and a tested engineering product may also be tested in different environmental testing equipment. In order to ensure the comparability of test results obtained for the same product under the same environmental testing conditions specified in the testing specifications, it is necessary to require the environmental conditions provided by the environmental testing equipment to be reproducible. This means that the stress levels (such as thermal stress, vibration stress, electrical stress, etc.) applied by environmental testing equipment to the tested product are consistent with the requirements of the same testing specification.
The repeatability of environmental conditions provided by environmental testing equipment is guaranteed by the national metrological verification department after passing the verification according to the verification regulations formulated by the national technical supervision agency. Therefore, it is necessary to require environmental testing equipment to meet the requirements of various technical indicators and accuracy indicators in the calibration regulations, and to not exceed the time limit specified in the calibration cycle in terms of usage time. If a very common electric vibration table is used, in addition to meeting technical indicators such as excitation force, frequency range, and load capacity, it must also meet the requirements of precision indicators such as lateral vibration ratio, table acceleration uniformity, harmonic distortion, etc. specified in the calibration regulations. Moreover, the service life after each calibration is two years, and after two years, it must be re calibrated and qualified before being put into use.
3. Measurability of environmental condition parameters
The environmental conditions provided by any environmental testing equipment must be observable and controllable. This is not only to limit the environmental parameters within a certain tolerance range and ensure the reproducibility and repeatability requirements of the test conditions, but also necessary for the safety of product testing, in order to prevent damage to the tested product and unnecessary losses caused by uncontrolled environmental conditions. The accuracy of parameter testing in various test specifications should not be less than one-third of the allowable error under test conditions.
4. Exclusion of environmental testing conditions
Each environmental or reliability test conducted has strict regulations on the category, magnitude, and tolerance of environmental factors, and excludes the infiltration of non test required environmental factors, in order to provide accurate basis for judging and analyzing product failure and failure modes during or after the test. Therefore, it is required that environmental testing equipment not only provide the specified environmental conditions, but also not allow additional environmental stress interference to the tested product. As defined in the verification regulations for electric vibration tables, the table leakage magnetic flux, acceleration signal-to-noise ratio, and total root mean square value ratio of in band and out of band acceleration. The accuracy indicators such as random signal inspection and harmonic distortion are all established as verification items to ensure the reliability of environmental testing conditions.
5. Safety and reliability of experimental equipment
Environmental testing, especially reliability testing, has a long testing cycle and sometimes targets high-value military products. During the testing process, testing personnel often need to operate or test around the site. Therefore, it is required that environmental testing equipment must have the characteristics of safe operation, convenient operation, reliable use, and long service life to ensure the normal progress of the testing itself. The various protection, alarm measures, and safety interlocking devices of the testing equipment should be complete and reliable to ensure the safety and reliability of the testing personnel, the tested products, and the testing equipment itself.