Q1 First, when using the temperature and humidity chamber for the first time, the user will typically experience the following situation the humidity unexpectedly indicated 100% in the test. What is the reason?
We should make sure that the wet bulb gauze is hung on the humidity sensor which is also the accessory of the sink. Besides, the wet blub gauze should wrap the temperature-sensing position of the sensor. There are also a few customers who often put the gauze in the wrong place, which will easily cause damage to the machine. Therefore, we should identify it carefully. Remember the top one is the temperature probe while the one below the sink is the humidity probe.
If the hanging mode is correct but the humidity still shows 100%, you need to check whether the wet bulb gauze is yellowing. Or if the wet bulb has been used for a long time, there will be too much mineral on the gauze, resulting in worse water absorption. If the gauze can not absorb water, the inaccurate data of humidity will be high. That is to say, we need to replace the wet bulb gauze or check whether there is water in the tank or the water level is low, making the water can not be absorbed.
You should check to see if the wet bulb gauze is becoming yellow if the hanging mode is proper but the humidity reading is still 100%. The gauze will have too much mineral on it if the wet bulb has been used for a long period, which will worsen the water absorption. If the gauze cannot absorb water, the humidity readings will be highly incorrect. That is to say, the water cannot be absorbed, thus we need to replace the wet bulb gauze or check to see if there is water in the tank or if the water level is too low.
Q2 What we should do if we haven’t utilized the temperature and humidity chamber for a long time?
1. You should remove the items from the chamber, unplug the power supply, the clean the interior and exterior of the chamber.
2. To prevent the door seal from adhering to the chamber, it should be separated from it by a paper strip or dusted with talcum powder.
3. The surroundings should have some level of dampness. Also, keep in mind that using plastic bags to cover the test chamber would make it difficult to get rid of the moisture. If not, the metal components will rust and harm other working parts.
4. The chamber must be located in an area that is cool, dry, and well-ventilated without direct sunlight. After moving the chamber, we need to keep the chamber placed smoothly.
Q3 How should the temperature and humidity chamber be cleaned and maintained?
It is advised that the chamber’s outside be cleaned one more time every year. Once a month, the humidifier’s water storage should be changed to ensure that the water is clean, and the humidifying water tray should be cleaned to ensure that the water flows smoothly.
Condenser dust needs to be routinely cleared. Every month, we should maintain the condenser by using a vacuum cleaner to remove the dust that has accumulated on it. Every three months, the test cloth needs to be changed. Moreover, before reinstalling the chamber, we should clean it by wiping it with a piece of cleaning cloth.
Q4 How can the various issues with the temperature and humidity chamber be fixed?
1. failure at a high temperature
We should examine the modulation damper with the air circulation system to see whether it is open if the temperature rises very slowly. Adjust the PID parameter values if the temperature is too high. And if there is over-temperature protection, the controller must be defective and needs to be replaced.
2. Low-temperature failure
Before testing, first, make sure the studio is dry. The test sample should be placed inside the chamber before the second test is conducted. The studio will have inadequate air circulation if there are too many samples. If not, it is time to request that the machine be inspected by qualified professionals.
3. Heat and humidity problems
The dry gauze on the wet bulb sensor could be to blame for this phenomenon. Thus, you must verify that the water level controller is operational and that the water tank of the wet bulb sensor can feed water as usual. The gauze may become hardened and dry because it cannot absorb water if the wet bulb sensor has been in use for a long time or if the water supply is pure. The gauze needs to be cleaned or replaced.
4. Alarm for water shortage
Lack of water in the tank could be the root of this kind of failure. As long as we fill the tank with enough pure or distilled water, the issue will be resolved. That could also be the result of the water tank being unclean, which prevents the tank float from rising. So we had better clean the tank until the float can move freely up and down.
5. Overheating protection faults
This kind of failure may be brought on by improper adjustment due to the humidification cylinder’s water shortage and excessive temperature regulation. Moreover, the temperature is typically set between 120 and 150 °C, which is regarded as a wide range.
6. Failure of the compressor overcurrent protection
If you run into this issue, make sure the compressor’s transition protection relay is not set to a very low setting or that the compressor cooling fan is not damaged. Please get in touch with a reputable manufacturer if there are any of these issues.
Q5 What causes the low-temperature test chamber’s significant difference in temperature? You can read an examination of the appearance of the uneven temperature in the content that follows.
1. insulation materials
The most important factor in ensuring the consistency of the low-temperature test chamber is the insulation material. If the insulation material is not handled properly, the test chamber’s uniformity deviation will be excessive. Typically, glass fiber and polyurethane insulation should be our two choices.
2. the airflow system
For the low-temperature test room to be uniform, the test chamber has air circulation. The heating air in the tube can be evenly sent into the chamber by using a fan blade if there is an air passage on the back of the apparatus to achieve a uniform temperature.
3. the sealing of the chamber and door
The temperature homogeneity of the test chamber will be significantly impacted if the seal is not made with seams or if air from the low-temperature test chamber seeps out of the chamber. As a result, the seal must be resistant to both high and low temperatures.
4. There is too much sample volume.
The test sample volume shouldn’t be too much when performing the test.
The test products must take up 1/3 of the chamber’s volume. To ensure the convection of the air surrounding and in the center, each product cannot be positioned too tightly.
5. The sample is not positioned in a way that makes sense.
The air outlet can neither be blocked by samples nor positioned near the air channel and must maintain a specific distance from the air exit. If not, the air circulation will be severely compromised. In order to verify that the air wheel is balanced with the air distribution, we should set the samples steadily.
6. The issue of the internal structure
When it comes to the interior structure and the space design, it might be challenging to achieve a uniform symmetrical structure, which can affect indoor heat convection and lead to certain inaccuracies regarding internal temperature uniformity. The metal plate primarily influences variables that are crucial for temperature uniformity, including the design of the air channel, the location of the heating tube, and the force of the draught fan.
Q6 What other performance indicators can be taken into consideration during the production commissioning process in addition to the temperature and humidity range?
As an illustration, take the high- and low-temperature chamber as an example. In addition to the temperature range, we will pay close attention to the following important indications throughout the pre-evaluation of the equipment and even during the back-end production commissioning process.
1. The pace at which temperature changes
It refers to the change in value in the internal chamber every minute, which is typically stated in terms of the units °C/min and K.
2. the temperature deviation
The temperature of each measuring point and the displayed temperature on the equipment should be recorded every minute once it has reached the predetermined value and is operating steadily. The data should be recorded thirty times.
We are looking for the difference between the set value and the maximum or minimum value in this process.
3. The temperature fluctuation
The maximum value of the temperature difference between each collection point in the operational environment is within 30 minutes by using the information gathered throughout the process of getting the temperature deviation.
Q7 Why is it necessary to mark the temperature uniformity and fluctuation together with the temperature deviation?
A crucial indicator is the test chamber’s temperature variation. Temperature fluctuations are a unique necessity for equipment like constant temperature and humidity test chambers, high and low temperature alternating hot and humid test chambers, and other machinery. Due to the substantial humidity swings and increased humidity error caused by temperature changes in the humidity and heat chamber, the allowed humidity deviation may be exceeded.
Q8 What are the dehumidification methods for the constant temperature and humidity chamber?
1. desiccant cooling technique
The fundamental idea behind desiccant cooling is that when the temperature of the air falls below the dew point, water will condense out of it, much like when you wear glasses in a warm room in winter and a film of mist condenses on the lens. In the temperature and humidity test, this is referred to as dehumidification. The best method to do this is to install an evaporator whose coolness can be controlled by our will. In order to lower the relative humidity in the air and hence lower the temperature by allowing the water vapor to condense into frost.
2. Air leakage to control humidity
This means that in order to create a fake steam leak, we must drill a ventilation hole in the main duct system. It refers to the interior water vapor will be expelled to an area with a constant temperature and humidity outside, removing the moisture therein directly to provide the dehumidifying effect.
3. Techniques for dehumidification with water spraying
The geographical season has a significant impact on the water spraying technique used for dehumidification. In a manner similar to dehumidification by freezing, this technique uses chilling to liquefy the water vapor in the air. This method of cold water spraying can be less expensive.
Q9 What are the common selection principles of the constant temperature and humidity chamber?
For every environmental or reliability test, some strict regulations are made on the category of environmental factors, value, and tolerance. And we should eliminate the environmental factors which are not required in the test. That is to say, the most important thing is to figure out the specified environment first.
The same type of product may be tested several times in a temperature-humidity test chamber, whereas an engineering product may be tested in various environmental test apparatuses. The environmental conditions, which are produced by the environmental test equipment, must be reproducible in order to ensure that the test results are similar under the specified environmental test parameters.
An engineering product’s use, storage, transportation, and other processes must be accurately or similarly simulated in a constant temperature and humidity chamber. Additionally, it must meet the requirements of test value for high temperature and low temperature, as well as the time of the test that is specified by different types of products. These requirements include uniformity of the temperature field and accuracy of the temperature control in accordance with defined test specifications. Only by doing this can we ensure an accurate replication of environmental conditions during the environmental test.
Safety and reliability
Environmental testing has a lengthy test cycle, particularly for reliability testing. The machine will occasionally test expensive military goods. The testers must do the operation or test around the scene during the testing process. Consequently, for the experiment to run normally, the environmental test equipment must be characterized by safe and simple operation, dependable use, extended working life, and so on.
Measurability and controllability
The tester must provide observable and controllable environmental circumstances, which are not only configured to restrict environmental parameters to a specified tolerance range but also for the safety of the experiment to prevent unneeded loss brought on by uncontrolled environmental conditions.