As one of the indispensable equipment in the laboratory, the constant temperature and humidity test chamber plays an important role in the accuracy and reliability of scientific research.
The constant temperature and humidity test chamber is a device that can simulate different temperature and humidity environments. It provides scientific researchers with a stable and repeatable experimental condition by controlling the temperature and humidity in the air.
The constant temperature and humidity test chamber produced by BOTO GROUP has high testing accuracy and can provide a great help in testing the reliability of your products!
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Precautions for constant temperature test
1. Low temperature switch shutdown time
How long is the appropriate shutdown time for a low-temperature switch? This is the key to this test. The basic principle is that the temperature rise caused by heat after the product is turned on can be reduced to be consistent with the ambient temperature in the environmental test chamber during the shutdown time. The agreement here is Refers to the temperature of all parts of the product, not some specific parts.
For some complex products, if it cannot be estimated, this time can be determined through experiments. The test method is to place temperature sensors on different devices inside the product, conduct actual tests to understand the rate of change of temperature recovery, and ultimately determine how long it will take to return to the same ambient temperature.
2. Recovery of test temperature
The time it takes for a test sample to reach an equilibrium state when the temperature test conditions are restored depends on its thermal inertia, that is, it depends on the shape, mass and structure of the test sample. The normal recovery time is 1 hour. Specific samples, especially equipment test samples, may need to be re-evaluated to determine the corresponding recovery time.
For constant temperature testing, it is often the case that the end time of the test is at night or on the weekend. At this time, you will encounter the problem of how to deal with this problem. It is generally recommended to return to normal temperature (25 degrees) after the test time is over, and keep the temperature test chamber working to maintain this temperature until the next day or working day. Jiayu Testing Network reminds us that in order to maintain the temperature test chamber studio, because for some products that generate a lot of heat, if the air does not circulate after the temperature test chamber is turned off, the ambient temperature will rise due to the heat of the product, and it is very likely that the ambient temperature will exceed happened. In addition, it should be noted that the sample needs to be kept working continuously, and the power cannot be cut off or the executed program or function can be terminated.
In some cases, when it is required to perform functional inspection before the end of the test, it is necessary to consider whether to continue to maintain the test temperature and wait until all functions have been checked before returning to normal temperature after working hours. Of course, in fact, extending the test time for one night or one or two days generally has little impact on the test results, and the risk is very low. If it returns to normal temperature in advance, the temperature of the temperature test chamber needs to be adjusted to the test temperature again after the working time returns. Consumer electronic products need to be working for at least one hour before performing relevant function tests.
3. Placement of samples in the temperature test chamber
Based on the principle of air convection, it can be placed in multiple layers. The following figure shows several placement diagrams. A and C are the correct placements. Placement B will affect the air convection in the test chamber and is not recommended.
Different test chambers can accommodate different test samples. The following table shows typical test chambers and corresponding size recommendations. Detailed size reference
In the figure below, the most critical thing is the minimum distance between the sample and the four walls of the test chamber. When preventing multiple samples, the minimum distance between samples can also refer to the recommended values in the table below.
4. Pre-test of test samples
Samples must be pre-tested before testing. The most important thing is that the software or other tools needed to be used in the test need to be tested at room temperature for more than half an hour before the test. Any problems that arise during the test need to be checked. For the record, it is not recommended to use samples with problems found during the test to conduct constant temperature tests, unless the test is only to find problems, and the test results cannot be used as the basis for final judgment. Generally recommended for room temperature
The sample with the problem will be found under the conditions, and the constant temperature test will be carried out after the problem is solved.
5. Test chamber wind speed
It is recommended that the impact of the test box wind speed on the temperature of the sample surface is less than 5 degrees. If possible, it is recommended that the test box wind speed be less than 0.5m/s. This is applicable to all temperature and humidity environment test projects.
6. Test chamber temperature change rate
The average temperature change rate of the test chamber shall not be higher than 1 degree per minute. This value is based on the average of temperature change rates no longer than 5 minutes.
7 Test chamber inlet air temperature
After the temperature of the test chamber is stabilized, the inlet air temperature must be within ±2 degrees of the specified temperature. If this accuracy cannot be guaranteed due to size factors of temperature and humidity, an accuracy of ±3 degrees can be accepted at temperatures above -25 degrees. For -25 degrees to -65 degrees can accept ±5 degrees accuracy.
8.Temperature curve setting
Some manufacturers provide two options for the temperature setting of the temperature test chamber. One is to calculate the execution time of the next step when the set temperature is reached within a certain range of the set temperature. The other is to reach the set temperature. Only then will it be determined that the set temperature has been reached. It is recommended that if you have a choice, choose the latter setting to ensure that the test time meets the requirements. Although the difference of a few minutes is within the acceptable range, you should still choose the latter for safety reasons.
This recommendation applies to all temperature-related tests using a temperature and humidity test chamber.
9. Test interruption
The interruption time of test conditions within the allowable error range is not recorded as an interruption (for example, the power supply of the temperature test chamber is restored after a short interruption, but the ambient temperature in the temperature test chamber is not affected)
BOTO reminds that if the interruption time of the test conditions exceeds the allowable error range, it is necessary to continue to restore the test conditions and conduct the test to ensure that the sum of the time before the test interruption and the continuous test time after the test conditions are restored after the test interruption meets the test requirements.
However, if the test is interrupted, the test will be saved and invalidated. The test needs to be completely re-executed, and the final result of the re-executed test will prevail.
10 Brackets for test products
Usually test chamber equipment manufacturers provide multi-position metal stainless steel brackets. The purpose of the test is to simulate the final actual use environment. Usually, it is less likely that the product will be placed on a metal rack or a good conductor of heat. Therefore, it is not recommended to place the product directly on the bracket during the test. It is usually necessary to prepare additional heat-conducting materials. The poorer material is placed on the pallet, and the final product is placed on the less thermally conductive material for testing.
It is recommended that you purchase a wooden board to place on the metal frame, and the product is finally placed on the wooden board for testing. What needs to be noted here is that since the wooden board will be subject to repeated temperature changes, it is necessary to purchase a wooden board with small deformation, otherwise it will be severely deformed and unusable after long-term use. In addition, it is recommended that the thickness of the wooden board should be more than 200mm, and the area should be larger than the projected area of the product placed. The actual product should not exceed the area of the wooden board when placed.