1. Reproducibility of environmental conditions It is beyond expectation to completely and accurately reproduce the environmental conditions existing in nature in the laboratory. However, within a certain tolerance range, people can completely and accurately simulate the external environmental conditions experienced by engineering products during use, storage, and transportation. This paragraph is summarized in the language of engineering, that is, "The environmental conditions (including the platform environment) created by the test equipment around the tested product should meet the environmental conditions and tolerance requirements specified in the product test specifications." For example, the temperature box used for military product testing should not only meet the requirements of the national military standard GJB150.3-86 and GJB150.4-86 according to different uniformity and temperature control accuracy. Only in this way can the reproducibility of environmental conditions in environmental tests be guaranteed.
2. Repeatability of environmental conditions An environmental test device may be used for multiple tests of the same type of product, and a tested engineering product may also be tested in different environmental test equipment. In order to ensure that the same product is The comparability of the test results obtained under the environmental test conditions specified in the same test specification inevitably requires the repeatability of the environmental conditions provided by the environmental test equipment. This means that the stress level (such as thermal stress, vibration stress, electrical stress, etc.) applied by the environmental test equipment to the tested product is consistent with the requirements of the same test specification. The repeatability of the environmental conditions provided by the environmental test equipment is guaranteed by the national metrological verification department in accordance with the verification procedures formulated by the national technical supervision agency. To this end, it must be required that the environmental test equipment can meet the requirements of various technical indicators and precision indicators in the verification regulations, and the use time should not exceed the time limit specified in the verification cycle. If the commonly used electric vibration table meets the technical indicators such as excitation force, frequency range, load capacity, etc., it must also meet the requirements of accuracy indexes such as lateral vibration ratio, table acceleration uniformity, harmonic distortion, etc. specified in the verification regulations And, the use period after each verification is two years, and more than two years must be re-verified before it can be put into use.
3. Measurable and controllable environmental parameters The environmental conditions provided by any environmental test equipment must be observable and controllable, not only to limit the environmental parameters within a certain tolerance range, but also to ensure the test conditions The reproducibility and repeatability requirements, and from the safety of product testing is also necessary, in order to prevent the environmental conditions out of control lead to damage to the tested product, bringing unnecessary losses. At present, various test specifications generally require that the accuracy of the parameter test should not be less than one-third of the error allowed by the test conditions.
4. Exclusiveness of environmental test conditions Each time an environmental or reliability test is carried out, there are strict regulations on the types, magnitudes and tolerances of environmental factors, and the environmental factors that are not required for the test are excluded from penetration in order to be included in the test Or provide accurate basis when judging and analyzing product failure and failure modes after the test, so the environmental test equipment is not allowed to add other environmental stress interference to the tested product in addition to the specified environmental conditions. The magnetic flux leakage of the table, the acceleration signal-to-noise ratio, and the ratio of the total rms value of the acceleration in and out of the band as defined in the electric vibration table verification regulations. Accuracy indicators such as random signal inspection and harmonic distortion are all verification items formulated to ensure the uniqueness of environmental test conditions.
5. Safety and reliability environmental test of test equipment, especially reliability test, the test period is long, the test object is sometimes a high-value military product. During the test, the test personnel often have to conduct patrols or test work around the site. Therefore, the environmental test equipment must have the characteristics of safe operation, convenient operation, reliable use, and long working life to ensure the normal conduct of the test itself. The various protection, warning measures and safety interlocking devices of the test equipment should be perfect and reliable to ensure the safety and reliability of the test personnel, the tested product and the test equipment itself.

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