Reproducibility

It is an unattainable task to completely and accurately reproduce the environmental conditions existing in nature in the laboratory. However, within a certain tolerance range, people can accurately and approximately simulate the external environmental conditions of engineering products in the process of use, storage, transportation, etc. This phrase is summed up in engineering language, that is, "the environmental conditions around the tested products (including platform environment) invented by the experimental equipment should satisfy the environmental rules of the product experimental standards." Requirements for parts and tolerances. If the temperature box used in the experiment of military products not only satisfies the experimental values and time of high and low temperature according to the rules of different types of products in the national military standard GJB150.3-86 and GJB150.4-86, but also satisfies the requirements of uniformity of temperature field and accuracy of temperature control in the experiment standard. Only in this way can we ensure the reproducibility of environmental conditions in environmental experiments.

Repeatability

An environmental experimental equipment may be used for many experiments of the same type of products, and an engineering product may also be tested in different environmental experimental equipment. In order to ensure the comparability of the experimental results of the same product under the environmental experimental conditions regulated by the same experimental standard, the environmental conditions provided by the environmental experimental equipment must be repeatable. 。 That is to say, the stress level (such as thermal stress, oscillatory stress, electrical stress, etc.) applied by environmental experimental equipment to the tested products is consistent with the requirements of the same experimental standard.

The repeatability of environmental conditions provided by environmental experimental equipment is guaranteed by the supply of qualified environmental conditions after verification by the National Metrology and verification department in accordance with the verification regulations formulated by the National Technical Supervision agency. Therefore, it is necessary to require the environmental experimental equipment to satisfy the requirements of the technical and precision objectives in the verification regulations, and not exceed the time limit of the verification cycle. If the widely used electric oscillator not only satisfies the technical objectives of exciting force, frequency range and load capacity, but also satisfies the requirements of the rules in the verification regulation such as transverse oscillation ratio, uniformity of table acceleration, harmonic distortion, and so on. Moreover, the service period after each verification is two years, and it is necessary to start from scratch for more than two years before it can be put into use. 。

Measurement and control

It is necessary to observe and control the environmental conditions provided by any environmental experimental equipment. This is not only to restrict the environmental parameters within a certain tolerance range, to ensure the reproducibility and repeatability of the experimental conditions, but also to start from the safety of product experiments, so as to prevent the damage of the tested products caused by uncontrolled environmental conditions and bring about no damage. Necessary loss. In general, the accuracy of parameter test should not be less than one third of the allowable error of experimental conditions in various experimental standards.

Exclusive nature

In every environmental or reliability experiment, there are strict rules for the categories, quantities and tolerances of environmental factors, and the penetration of non-experimental environmental factors is excluded so as to provide the exact basis for judging and analyzing product failure and defective forms after the experiment or the end of the experiment. Therefore, environmental experimental equipment is required not to be allowed except for the regular environmental conditions. Adding other environmental stress disturbance to the product. For example, magnetic flux leakage, acceleration signal-to-noise ratio and total root mean square ratio of in-band and out-of-band acceleration are limited in the verification regulation of electric oscillator. Accuracy targets such as random signal checking and harmonic distortion are all verification items to ensure the uniqueness of environmental experimental conditions.

Safety and reliability

Environmental experiment, especially reliability experiment, has a long period of experiment. The object of experiment is sometimes a military product of high value. In the process of experiment, the experimenters often have to operate or test around the scene. Therefore, it is necessary for environmental experimental equipment to have the characteristics of safe operation, convenient operation, reliable use and long working life, so as to ensure the normal progress of the experiment itself. That's ok. All kinds of protection, alarm measures and safety interlocking devices of experimental equipment should be perfected and reliable to ensure the safety and reliability of the experimenters, the tested products and the experimental equipment themselves.