Home entertainment audio-visual equipment and automotive electronics are one of the key products of many manufacturers, and during product development process must simulate the adaptability of temperature and electronic characteristics at different temperatures. However, when using the general oven or constant temperature and humidity test chamber to simulate the temperature environment, both them have a test area equipped with a circulating fan, so there will be wind speed problems in test area. During the test, the temperature uniformity is balanced by rotating the circulating fan. Although the temperature uniformity of the test area can be achieved through the wind circulation, the heat of testing product will also be taken away by the circulating air, which will be significantly inconsistent with the actual product in the wind-free use environment (such as the living room, indoor). Because of the relationship of wind circulation, the temperature difference of testing product will be nearly 10°C, in order to simulate the actual use of environmental conditions, many people will misunderstand that only the test machine can produce temperature (such as: oven, constant temperature and humidity test chamber) can carry out natural convection test, in fact, this is not the case. In the specification, there are special requirements for wind speed, and a test environment without wind speed is required. Through the natural convection test equipment (no forced wind circulation test), the temperature environment without fan is generated (natural convection test), and then the test integration test is carried out to detect the product temperature. This solution can be applied to the actual ambient temperature test of household related electronic products or confined Spaces (such as: Large LCD TV, car cockpit, car electronics, laptop, desktop computer, game console, stereo... Etc.).
Indoor environment without wind circulation and solar radiant heat irradiation:
Through the natural convection tester, simulate the client's actual use of the real air conditioning convection environment, hot spot analysis and heat dissipation characteristics of the product evaluation, such as LCD TV is not only to consider its own heat dissipation, but also to evaluate the impact of thermal radiation outside the window, thermal radiation for the product may produce additional radiant heat above 35°C.
Comparison of wind speed and IC testing product:
When the ambient wind speed is faster, the IC surface temperature will also take away the IC surface heat due to the wind cycle, resulting in faster wind speed and lower temperature, when the wind speed is 0 the temperature is 100℃, but when the wind speed reaches 5m/s, the IC surface temperature has been below 80℃.
Unforced air circulation test:
According to the specification requirements of IEC60068-2-2, in the high temperature test process, it is necessary to carry out the test conditions without forced air circulation, the test process needs to be maintained under the wind-free circulation component, and the high temperature test is carried out in the test furnace, so the test cannot be carried out through the constant temperature and humidity test chamber or oven, and only natural convection tester can be used to simulate the free air conditions.
Description of test conditions:
Test specification for unforced air circulation: IEC-68-2-2, GB2423.2, GB2423.2-89 3.3.1
Unforced air circulation test: The test condition of unforced air circulation can simulate the free air condition well
GB2423.2-89 3.1.1:
During measuring under free air conditions, when the temperature of the test sample is stable, the temperature of the most hot spot on the surface is higher than the ambient atmospheric temperature of 5°C or more, it is a heat dissipation test sample, otherwise it is a non-heat dissipation test sample.
GB2423.2-8 10(Test heat dissipation test sample temperature gradient test) :
A standard test procedure is provided to determine the adaptability of thermal electronic products (including components, equipment level other products) to use at high temperatures.
Test requirements:
a. Testing machine without forced air circulation (equipped with a fan or blower)
b. Single test sample
c. The heating rate is not more than 1℃/min
d. After the temperature of test sample reaches stability, the test sample is energized or the home electrical load is carried out to detect the electrical performance
