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Test Index of Constant Temperature and Humidity Testing Machine

Apr 27, 2022

Test Index of Constant Temperature and Humidity Testing Machine

The accuracy indexes of parameters of constant temperature and humidity testing machine (such as temperature, humidity, etc.) are the results of detection under no-load state. Some customers might ask: don't the test results under no-load and non-no-load are the same? It must be different. Once the constant temperature and humidity testing machine is placed into the tested product, it will have an impact on the uniformity of environmental parameters in the test chamber. The larger the space occupied by the tested product, the more serious the impact will be. Why? A large number of measured test data show that the temperature difference between the windward side and the leeward side in the flow field can reach 3 ~ 8 ℃, which can be more than 10 ℃ in severe cases. Therefore, several requirements outlined above must be met as far as possible to ensure the uniformity of environmental parameters around the tested product.

According to the principle of heat conduction, the temperature of the air flow near the box wall is usually 2 ~ 3 ℃ different from the center temperature of the flow field, and may reach 5 ℃ at the upper and lower limits of high and low temperature. The difference between the temperature of the box wall and the temperature of the flow field near the box wall is 2 ~ 3 ℃ (depending on the structure and material of the box wall). The greater the difference between the test temperature and the external atmospheric environment, the greater the temperature difference. Therefore, the space within the distance from the box wall (100 ~ 150mm) is unusable.

Relevant standards stipulate that the wind speed in the warm and wet box shall be less than 1.7m/s during the environmental test. For the test itself, the smaller the wind speed, the better. Excessive wind speed will accelerate the heat exchange between the surface of the test piece and the flowing air flow in the box, which is unfavorable to the authenticity of the test. However, in order to ensure the uniformity in the chamber, it is necessary to have circulating air in the chamber. However, for the rapid temperature change high and low temperature test chamber and the multi factor comprehensive environmental test chamber such as temperature, humidity and vibration, in order to pursue the temperature change rate, it is necessary to speed up the flow rate of circulating air flow in the chamber, and the wind speed is usually 2 ~ 3M / s. Therefore, the wind speed limit is different for different purposes.

In order to more accurately simulate the actual environmental conditions suffered by products in nature, it is necessary to ensure that the surroundings of the tested products are under the same temperature environmental conditions in the environmental test. Therefore, the temperature gradient and temperature fluctuation in the test chamber must be limited.

In the constant temperature and humidity testing machine, the humidity is mostly measured by the dry wet ball method. According to the manufacturing standard of environmental test equipment, the relative humidity deviation should be ± 2.3% RH. In order to meet the requirements of humidity control accuracy, the temperature control accuracy of humidity test chamber is high, and the temperature fluctuation is generally less than ± 0.2 ℃. Otherwise, it is difficult to meet the requirements of humidity control accuracy.

Acey new energy provides various kinds of environmental test equipment for laboratory use.

Constant temperature and humidity test chamber Battery environmental testing chamber

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