Technical specifications for measurement verification of hot and cold shock test chambers

In order to ensure the linearity of air quality parameters in order to ensure the linearity of air quality parameters in the natural environment test standards in standard experimental equipment, technical management agencies and various industrial departments have also formulated a series of technical specifications
for measurement and verification of environmental test equipment and inspection instrument equipment.
For example, the Republic of China standardizes GB5170 "Measurement and verification method of main parameters of electrical and electronic commodity environmental test equipment", and JJG190-89 "Technical Specification for Measurement and Verification of Electrodynamic Vibration Test Bench System Software" implemented
by the Bureau of Technical Supervision.
This kind of measurement verification technical specifications are an important part of the selection of natural environment and reliability testing equipment and equipment, and experimental machinery and equipment that do not conform to the provisions of this measurement verification technical specification are not allowed to invest
funds.
The reasons for such requirements are as follows: 1.
After being embedded in the shell of the experimental piece, a smooth safety channel is occupied, and the smaller safety channel will cause the cyclone water flow to increase
.
Speed up the heat exchanger
between the cyclone and the test piece.
This is inconsistent with the reproduction of natural environment standards, because the relevant specifications require that the air flow rate around the first sample in the experimental chamber should not exceed 1.
7m/s for experiments involving temperature and natural environment, so as to avoid unrealistic heat
conduction caused by the first sample of the experiment and the surrounding atmosphere.
When fully loaded, the average wind force in the experimental box is 0.
6~0.
8m/s, not more than 1m/s, considering the indoor space and total area ratio required by the two provisions of a) and b), the wind force of the flow field will expand (50~100)%, and the average high wind force will be (1~1.
7)m/s
.
Consider the provisions of the
standard.
If the volume of the experimental piece or the total area of the windward break are not limited in the experiment, the cyclone wind force will be expanded to exceed the high wind force required by the experimental specifications during the specific experiment, and the validity of the experimental results will be doubted
.
2.
According to the basic principle of heat conduction, the temperature of the cyclone around the box wall is generally 2~3 °C away from the temperature of the flow field management center, and the special discount on the upper and lower left and right of the high and low temperature test will exceed 5 °C
.
The temperature of the box wall and the temperature of the flow field around the box wall are 2~3 °C (depending on the structure and raw materials of the box wall) The greater the distance between the experimental temperature and the external air pollution, the greater the temperature difference, therefore, the indoor space within the distance from the box wall (100~150mm) can not use the indoor space
。 3.
The precision index values of air quality parameters in the chamber working chamber (such as temperature, environmental humidity, corrosion resistant foundation settlement rate, etc.
) are all the results of the test under full load, if embedded in the experimental piece, the uniformity of the air quality parameters in the chamber working of the environmental test chamber will cause harm, the larger the indoor space occupied by the experimental piece, the more serious
such hazards are.
The evaluation experimental statistics show that the temperature difference between the windward side and the leeward side in the flow field can exceed 3~8 °C, and it can be as large as about
10 °C in more serious cases.
Therefore, it is important to consider the two provisions of a] and b] as much as possible to ensure the uniformity of the air quality parameters around the tested product
.