Examination of technical indicators of temperature shock test chamber

Wind Speed Requirements

Various temperature change test standards specify wind speed limits within the test chamber, typically requiring it to be less than or equal to 2 m/s. This restriction ensures that the test product is not exposed to excessive airflow, which could cause abnormal heat transfer and distort the actual performance conditions. A controlled wind speed helps achieve rapid and uniform temperature distribution inside the chamber. However, if the wind speed is too high, it may cause uneven heat exchange between the surface of the product and its internal components, leading to inaccurate simulation of real-world thermal conduction processes.

Absolute Humidity Requirements

MIL-STD-810F does not impose specific humidity requirements because most products are made from materials that are not significantly affected by humidity during temperature impact tests. However, it notes that porous materials, such as fiber-based ones, can absorb moisture, which may expand when frozen at low temperatures, potentially causing damage. Therefore, it is recommended to control the humidity in the test chamber. Typically, the absolute humidity should be kept below or equal to 20 g/m³ to prevent such issues.

Air Temperature Recovery Time Requirement

GJB150.5 (equivalent to MIL-STD-810 C/D) and GB2423.22 (similar to IEC60068-2-14) both require the air temperature recovery time to be less than or equal to the test duration, meaning the time it takes for the product to reach thermal stability. In contrast, MIL-STD-810F sets a stricter limit, requiring it to be less than or equal to 5 minutes. This requirement ensures the test chamber has sufficient thermal capacity to simulate true temperature shock conditions without prolonged stabilization periods.

Difference Between Chamber Wall Temperature and Test Temperature

Standards also define limits on the difference between the chamber wall temperature and the test temperature. This is to avoid excessive radiant heating effects caused by large temperature differences, which could lead to uneven temperature distribution on the test product. Generally, the maximum allowed difference is ≤ 3% for high-temperature testing and ≤ 8% for low-temperature testing.

Understanding these key technical specifications of a temperature shock test chamber not only enhances your knowledge of the testing process but also aids in selecting the right equipment. Moreover, it provides valuable insights into proper usage and maintenance, ensuring accurate and reliable test results over time.

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