Constant temperature and humidity test box also called high low temperature alternating wet heat test box, programmable constant temperature and humidity test enginery, is used to test all kinds of materials, such as: electronics, electrical appliances, communication, instrument, vehicles, plastic products, metal, food, chemical, building materials, medical, aerospace products, heat resistance, cold resistance, resistance to dry, can the anoxic condition testing equipment. According to the testing requirements should not only have the control of the temperature, while providing humidity control, this process is as follows:
A, constant temperature and humidity test cases of the process of temperature
The temperature of the test is mainly high-power resistance wire,China clinical thermometer manufacturer due to the requirements of the test box heating rate is bigger, so the test cases with temperature system is divided into humidifying and dehumidification two subsystem;
Second, constant temperature and humidity test box cooling process
Cooling namely refrigeration, test box of refrigeration method all is mechanical refrigeration and the auxiliary liquid nitrogen refrigeration, mechanical refrigeration adopted steam compression type refrigeration, they are mainly the compressor, the condenser, evaporator and the throttle body composition, constant temperature and humidity test box if the need to achieve greater temperature requirements of 55 ℃ low-or below, single stage cooling to meet meet the requirements, so the test cases by general refrigeration way cascade type refrigeration.
Three, constant temperature and humidity test box and wet process
Constant temperature and humidity test box and wet process is actually improve water vapor pressure points, first add wet way is to the constant temperature and humidity test box wall spray water, through the control the water surface water saturation pressure under control. Box of wall surface water form a larger surface, in the face of the way through to spread to join the vapor pressure make test box relative humidity increases, this method appeared in the 1950 s.China digital sphygmomanometer manufacturer Because at that time to humidity control is mainly by mercury the electricity connecting point conductive table simple switch quantity adjustment, for big lagging behind the hot water tank of water temperature control adaptability is bad, so the transition process control is long, can not meet the moisture content of alternating with damp and hot demand more need, the more important it is to the box in wall spray, inevitably have rain water droplets in the product to try to try different levels of pollution is formed.
Four, constant temperature and humidity test box dehumidification process
Test box dehumidification two different ways: mechanical refrigeration dehumidifier and drying dehumidifying.
1, machinery cooling dehumidification air cooling dehumidification principle to the temperature of dew point, make greater than saturated moisture content of vapor condensation exhalation, thus reduce the humidity.
2, desiccant dryers is to use air pump will test out the air, China flexible thermometer manufacturerand will dry air injection, and at the same time will be wet air into recycled dry for dry, dry after the test and into, so repeated cycles dehumidifier.
Now most constant temperature and humidity test box adopts a dehumidification way before method, a method after dehumidification, needs to increase the dehumidifier or chemistry dehumidifier, can make the temperature reaches 0 ℃ the dew point. Suitable for special requirement to the occasion, but the cost is relatively high.