Five points to be paid attention to in laboratory equipment of selecting environmental test box

Environmental test chamber is a kind of common laboratory equipment Environmental test chamber simulates the natural environment and climate by means of science and technology It can carry out many kinds of tests, such as high temperature test, low temperature test, solar radiation test, moisture-proof test, etc For the selection of laboratory equipment test box, five basic principles should be paid attention to: 1 The measurability of environmental condition parameters The environmental conditions provided by any environmental test equipment must be observable and controllable, which is not only to limit the environmental parameters within a certain tolerance range, To ensure the reproducibility and repeatability of test conditions, and from the safety of product test is also necessary, in order to prevent environmental conditions out of control leading to the damage of the tested products, resulting in unnecessary losses At present, the accuracy of parameter test should not be less than one third of the allowable error of test conditions 2 Repeatability of environmental conditions one environmental test equipment may be used for multiple tests of the same type of product, and one engineering product may be tested in different environmental test equipment In order to ensure the comparability of test results of the same product under the environmental test conditions specified in the same test specification, It is necessary that the environmental conditions provided by the environmental test equipment should be repeatable That is to say, 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 according to the verification regulations formulated by the national technical supervision organization Therefore, it must be required that the environmental test equipment can meet the requirements of various technical indexes and precision indexes in the verification regulation, and the use time shall not exceed the time limit specified in the verification cycle For example, in addition to the technical indexes such as exciting force, frequency range and load capacity, the widely used electric vibration table must also meet the requirements of accuracy indexes such as transverse vibration ratio, table acceleration uniformity and harmonic distortion specified in the verification regulation, and the service period after each verification is two years, and it can only be put into use after it has passed the re verification for more than two years 3 The reproducibility of environmental conditions can not be expected to reproduce the environmental conditions existing in nature completely in the laboratory However, within a certain tolerance range, people can simulate the external environmental conditions of engineering products in the process of use, storage, transportation and so on This passage is summarized in engineering language, that is, "the environmental conditions (including platform environment) around the tested product created by the test equipment shall meet the requirements of environmental conditions and tolerance specified in the product test specification" For example, the temperature box used for military product test shall not only meet the requirements of national military standards gjb150.3-86 and gjb150.4-86 according to different uniformity and temperature control accuracy Only in this way can we guarantee the reproducibility of environmental conditions in environmental tests 4 The safety and reliability environment test of test equipment, especially the reliability test, has a long test cycle Sometimes the test object is the military products with high value During the test process, the test personnel often need to conduct patrol inspection or test around the site, Therefore, it is required that the environmental test equipment must have the characteristics of safe operation, convenient operation, reliable use and long working life, so as to ensure the normal operation of the test itself All kinds of protection, alarm measures and safety interlock devices of test equipment shall be perfect and reliable to ensure the safety and reliability of test personnel, tested products and test equipment 5 Exclusiveness of environmental test conditions every time environmental or reliability test is carried out, there are strict regulations on the category, quantity and tolerance of environmental factors, and environmental factors not required for the test are excluded from penetration, so as to provide exact basis for judging and analyzing product failure and failure mode during or after the test, Therefore, the environmental test equipment is required to provide the specified environmental conditions, and it is not allowed to add other environmental stress interference to the tested products For example, the leakage of magnetic field, the signal-to-noise ratio of acceleration, and the ratio of the total root mean square of acceleration in and out of the band defined in the verification regulation of electric vibration table The test of random signal, harmonic distortion and other precision indexes are all verification items formulated to ensure the reliability of environmental test conditions.