Engineers engaged in the study of environmental conditions of engineering products have summarized the environmental conditions and the environmental conditions induced by human activities into a series of test standards and norms. Through these standards to conduct environmental and reliability tests of engineering products. Therefore, when selecting environmental test chambers, we mainly rely on the test specifications and test standards of engineering products.
Selection criteria of environmental chamber
1. Volume Selection
When the tested product is placed in an environmental chamber for testing, the working chamber volume of the climatic environment test chamber should be at least 3 to 5 times the outer volume of the tested product.
2. Selection of Temperature Range
The range of foreign temperature test chambers is generally -73~+177°C or -70~180°C. Most domestic manufacturers’ products are -80~+130°C, -60~+130°C, -40~+130°C, and high temperature to 150°C. These temperature ranges usually meet the needs of most military and civil temperature tests in the country.
3. Selection of Humidity Range
The temperature index of environmental test chambers at home and abroad is generally 20~98% RH or 30~98% RH. If the temperature humidity chamber does not have a dehumidification system, the temperature range is 60 to 98%. This type of test chamber can only be tested for high humidity, but it is much cheaper. It is worth noting that the corresponding temperature range or minimum dew point temperature should be indicated after the humidity indicator. Because relative humidity is directly related to temperature.
For the same absolute moisture content, the higher the temperature, the lower the relative humidity. For example, the absolute moisture content is 5 g/kg, when the temperature is 29°C, the relative humidity is 20% RH. And when the temperature is 6°C, the relative humidity is 90% RH. When the temperature drops below 4 ° C and the relative humidity exceeds 100%, condensation will occur in the box.
4. Choice of Control Methods
The temperature humidity test chambers have two conditions:
- Constant test chamber
- Alternating test chamber
Users should choose according to actual needs.
5. Selection of Temperature Change Rate
Ordinary high and low temperature test chambers have no index of cooling rate. And the time from ambient temperature cooling to the nominal minimum temperature is generally 90 to 120 minutes.
However, The high and low temperature alternating test chamber and the high and low temperature alternating damp heat test chamber all have the requirements of variable temperature speed. And the variable temperature rate generally requires 1 ° C / min, and the speed can be adjusted within the range of this rate. The rapid temperature change test chamber has a faster temperature change rate. And the temperature rise and temperature drop rate can reach 30 ° C/min or more in some temperature ranges.
6. Wind Speed
According to the relevant standards, the wind speed in the temperature humidity chamber should be less than 1.7 m/s when conducting environmental tests. However, the rapid temperature change test chamber and the multi-factor comprehensive environmental test chamber such as temperature, humidity and vibration are required to accelerate the flow rate of the circulating airflow in the tank. The wind speed is usually 2~3 m/s.
7. Temperature Fluctuation
Temperature fluctuations are a relatively easy to implement parameter. The actual temperature fluctuations of most test chambers produced by all environmental test chamber manufacturers can be controlled within ±0.3 °C.
8. Temperature Field Uniformity
In fact, many standards have clear specifications for temperature field uniformity. For example, IEC 68-2-3 specifies that the temperature tolerance is ±2 °C, including the absolute error of the measurement, the slow temperature change and the temperature difference in the temperature cabinet. Therefore, the temperature of any two points in the test cabinet is kept as small as possible at all times.
9. Temperature Precision Control
Most of the humidity measured in the environmental test chamber is dry and wet bulb method, The relative humidity deviation should be ±2% RH or ±3% RH. In order to meet the requirements of temperature control accuracy, the temperature fluctuation is generally less than ± 0.2 ° C. Otherwise, it is difficult to meet the requirements of humidity control accuracy.
10. Choice of Cooling Method
In general, there two cooling form in the environmental test chamber.
- Water-cooled versions
The choice of cooling method should be based on the actual situation of the laboratory. Water cooling is a top priority when conditions permit.
11. Other Considerations
For the selection of temperature humidity chamber, in addition to some of the principles and specific technical indicators described earlier in this article, there are some factors that should be valued and considered.
- Performance / cost performance
On the basis of fully researching the technical parameters and reliability of environmental test chamber, cost performance is an important factor that should be considered.
- The degree and ability to meet user needs
The user orders a temperature and humidity environmental test chamber, the requirements of which vary according to the needs of the product test. For example, some users use the temperature humidity vibration combined test chamber to test the parts or components of products and environmental stress screening tests. At this time, the forced dehumidification capability of the equipment and the possibility of an additional air drying system are items that the user should be concerned with.
- After-sales service and equipment failure handling capacity
Last but not least,we are a manufacturer of battery testing equipment and environmental test chamber with 13 years of production and R&D experience. If you need battery testing equipment or environmental chamber,please consult us!