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          How to choose an environmental test chamber

          The types of natural environmental factors and induced environmental factors that exist in the earth's surface and the atmosphere are not yet counted, and there are no more than a dozen factors that have a greater impact on the use and life of engineering products (equipment). Engineers engaged in the study of environmental conditions of engineering products classify the environmental conditions induced by nature and human activities into a series of test standards and specifications to guide the environmental and reliability tests of engineering products. For example, instructing military products to conduct environmental tests GJB150 - National Military Standard of the People's Republic of China "Environmental Test Methods for Military Equipment", GB2423 for guiding environmental testing of electrical and electronic products - National Standard of the People's Republic of China "Guidelines for Environmental Test Methods for Electrical and Electronic Products", etc. . Therefore, the main basis for our selection of environmental and reliability test equipment is the test specifications and test standards for engineering products.

          Secondly, in order to standardize the tolerance of environmental test conditions in test equipment and ensure the control accuracy of environmental parameters, the national technical supervision agencies and various industrial departments have also formulated a series of verification procedures for environmental test equipment and instruments. The People's Republic of China National Standard GB5170 "electric and electronic products basic parameters of environmental testing equipment, test methods", and if the National Technical Supervision promulgated JJG190 - 89 "electric system vibration test stand trial test procedures" and the like. These verification procedures are also an important basis for selecting environmental and reliability test equipment. Test equipment that does not meet the requirements of these verification procedures is not allowed to be put into use.

          Basic principle of equipment selection

          The selection of environmental and reliability test equipment should follow the following five basic principles:

          1. Reproducibility of environmental conditions

          It is an elusive thing to completely and accurately reproduce the environmental conditions that exist in nature in the laboratory. However, within a certain tolerance range, people can correctly and correctly simulate the external environmental conditions experienced by engineering products during use, storage, transportation and the like. This passage is summarized in the language of the project, that is, " the environmental conditions (including the platform environment) created around the test equipment created by the test equipment should meet the environmental conditions and tolerances specified in the product test specifications. " The test products for military tank temperature not only to meet military standard GJB150.3 - 86, GJB150.4 - 86 in the control accuracy requirements depending on the uniformity and temperature. Only in this way can the reproducibility of environmental conditions in environmental tests be guaranteed.

          2 , the reproducibility of environmental conditions

          An environmental test equipment may be used for multiple tests of the same type of product, and one engineered product may also be tested in different environmental test equipment in order to ensure that the same product is in the same test test. The comparability of the test results obtained under the conditions necessarily requires the environmental conditions provided by the environmental test equipment to be reproducible. That is to say, the stress level (such as thermal stress, vibration stress, electrical stress, etc.) applied to the product under test by the environmental test equipment 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 after passing the verification according to the verification procedures formulated by the national technical supervision agency. To this end, environmental testing equipment must be required to meet the requirements of various technical indicators and accuracy indicators in the verification procedures, and the time limit specified in the verification period should not exceed the time limit. If the use of the very common electric vibration table meets the technical indicators such as excitation force, frequency range, load capacity, etc., it must also meet the requirements of the accuracy index such as the lateral vibration ratio, the uniformity of the table surface acceleration, and the harmonic distortion specified in the verification regulations. And the use period after each verification is two years, more than two years must be re-qualified before they can be put into use.

          3. Exclusivity of environmental test conditions

          Every 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 required for non-tests are excluded from infiltration in order to judge and analyze product failures during or after the test. In the case of failure mode, the exact basis is provided. Therefore, the environmental test equipment is not allowed to attach other environmental stress interference to the test product except for the specified environmental conditions. For example, the leakage magnetic field of the table, the acceleration signal-to-noise ratio, and the ratio of the total rms value of the in-band and out-of-band acceleration are defined in the electric vibration table verification procedure. Accuracy indicators such as random signal test and harmonic distortion are all verification items to ensure the uniqueness of environmental test conditions.

          4 , the controllability of environmental condition parameters

          The environmental conditions provided by any environmental test equipment must be observable and controllable, not only to limit environmental parameters to within certain tolerances, but also to ensure reproducibility and repeatability of test conditions. Moreover, it is necessary to start from the safety of the product test, in order to prevent the damage of the test product caused by the out of control of the environmental conditions, resulting in unnecessary losses. At present, the accuracy of the parameter test generally required in various test specifications should not be less than one third of the error allowed by the test conditions.

          ?€€ 5 , the safety and reliability of the test equipment

          Environmental tests, especially reliability tests, have long test cycles. The test objects are sometimes high-value military products. During the test, testers often have to conduct inspections or test work around the site. Therefore, environmental test equipment must be operated. Safe, easy to operate, reliable to use, long working life, etc., to ensure the normal operation 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 products and the test equipment itself.

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          亚洲 欧美 图片 自拍 视频
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