Constant temperature and humidity testing machine parameters (such as temperature, humidity, etc.) are indicators of accuracy in the test results under no-load conditions. Some customers may question: The results of the following tests are not the same as those for non-idle and non-idle tests. Certainly not the same, once the temperature and humidity test chamber is placed into the tested product, the environmental parameters of the chamber of the test chamber are Uniformity will have an effect, and the greater the space occupied by the tested product, the more serious this effect will be. Why? We have conducted a large number of actual test data to show that the temperature difference between the windward side and the leeward side in the flow field can reach 3~8Â°C, and when it is severe, it can reach 10Â°C or more. Therefore, several requirements outlined above must be satisfied to ensure the uniformity of the environmental parameters around the tested product.
According to the principle of heat conduction, the temperature of the air flow near the wall is usually 2~3Â°C different from the center temperature of the flow field, and it may reach 5Â°C when the upper and lower limits of high and low temperatures are reached. The temperature of the tank wall differs from the temperature of the flow field near the tank wall by 2 to 3Â°C (depending on the structure of the tank wall and the material), the greater the difference between the test temperature and the external atmospheric environment, the greater the temperature difference, and therefore, the distance from the tank. The space within the distance of the wall (100-150mm) is an unusable space.
The relevant standards stipulate that the wind speed in the temperature and humidity cabinet should be less than 1.7m/s during the environmental test. For the test itself, the smaller the wind speed, the better. If the wind speed is too high, the airflow on the surface of the test piece and the inside of the cabinet will be accelerated. The heat exchange is not good for the authenticity of the test. However, in order to ensure the homogeneity of the test chamber, it is necessary to have circulating air in the test chamber. However, rapid temperature changes in high and low temperature test chambers and environmental test chambers such as temperature, humidity, vibration, etc., in order to pursue a variable temperature rate, it is necessary to accelerate a flow rate of the circulating air in the box, and the wind speed is usually 2 to 3 m/s. Therefore, the speed limit is not the same for different uses of the material.
In order to more accurately simulate the actual environmental conditions that the product has suffered in nature, it must be ensured in the environmental test that the periphery of the tested product is under the same temperature and environmental conditions. For this purpose, the temperature gradient in the test chamber must be The temperature fluctuation is limited. In the general rule of the National Army standard GJB150.1-86 equipment environmental test method, it is stipulated explicitly that â€œthe temperature of the measurement system near the test sample should be within Â±2Â°C of the test temperature, and its temperature work should not exceed 1Â°C/m or a total large value. 2.2 Â°C (test sample does not work)".
Most of the humidity measured in the constant temperature and humidity testing machine adopts the wet-and-dry ball method and the requirements of manufacturing standards for environmental testing equipment. The relative humidity deviation should be within Â±2.3% RH. In order to meet the requirement of humidity control accuracy, the temperature control accuracy of the humidity chamber is relatively high, and the temperature fluctuation is generally less than Â±0.2Â°C. Otherwise it will be difficult to meet the requirements of humidity control accuracy.
Ai Siwei offers you a selection of constant temperature and humidity testing machine products, you are welcome to inquire the details of the product! There are many different types of products, and there are subtle differences in different products. The company provides you with a full range of solutions. Welcome customers to inquire or visit the factory!
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