Selection Guide For Temperature Humidity Chambers 

The environmental chamber is an indispensable reliability environment testing equipment for testing quality of electronic, electrical, instrumentation and other products. Usually the purchaser may have some doubts in the process of purchasing the temperature humidity testing equipment, so what aspects should be paid attention to when purchasing the temperature humidity chambers?

1.Selection of Volume

When the test product is placed in the temperature humidity testing chamber for testing, in order to ensure that the atmosphere around the test product can meet the environmental test conditions specified in the test specification, the rules should be followed when selecting and purchasing:

(1)The volume of the tested product shall not exceed 20 to 35% of the effective working space of the test chamber. It is recommended to use no more than 10% for products that generate heat during the test.

(2)The ratio of the windward section area of the tested product to the total area of the test box studio on the section is not more than 35-50%.

(3)The distance between the outer surface of the tested product and the wall of the test box should be kept at least 100-150 mm.

To sum up the above three points, the working chamber volume of the environment test box should be at least 3-5 times of the outer volume of the tested product.

2.Selection of Temperature Range

At present, the temperature test chambers produced by foreign environmental chamber manufacturers generally range from -73℃ to +177℃ or -70℃ to +180℃. The temperature test chambers produced by most of China's temperature humidity testing chamber  manufacturers generally have a range of -80℃ to +130℃, -60℃ to +130℃, and -40℃ to +130℃.These temperature ranges usually meet the needs of most products for temperature testing. Temperature limits should not be raised blindly unless there are special requirements, such as installation location close to the engine and other heat source products.  Because the higher the upper limit temperature, the greater the temperature difference between the inside and outside of the test chamber, the worse the uniformity of the flow field inside the test chamber, the smaller the available volume. On the other hand, the higher the upper limit temperature value, the higher the heat resistance of the insulating material in the interlayer of the test chamber wall. The higher the requirements for the sealing of the test chamber, the higher the manufacturing cost of the box.

3.Selection of Humidity Range

Most of the humidity indicators given by environmental test boxes at home and abroad are 20%-98% or 30%-98%. If there is no dehumidification system in the humidity-heat test box, the humidity range is 60%-98%. This kind of temperature humidity testing equipments can only do high humidity test, but its price is much lower. It is worth noting that the corresponding temperature range should be indicated after the humidity indicator. Because the relative humidity is directly related to the temperature, for the same moisture content, the higher the temperature, the smaller the relative humidity, such as the moisture content is 5g/Kg, and the relative humidity is 20% at a temperature of 29℃. When the temperature is 6℃, the relative humidity is 90%. When the temperature drops below 4℃, the relative humidity exceeds 100%, condensation will appear in the box.

4.Selection of System Control Hardware

In terms of hardware selection, it is mainly based on customer's actual operation, test use and product cost.

The temperature humidity chamber is indispensable equipment in laboratory. It is hoped that the above contents will be helpful for purchasers to select temperature humidity chamber.