An article to understand the constant temperature and humidity test chamber

A constant temperature and humidity test chamber is also called: a constant temperature and humidity testing machine, a constant temperature and humidity experimental chamber, a programmable humidity and heat alternating test chamber, or a constant temperature machine. This equipment simulates the natural environment’s temperature and humidity. It tests products at a constant temperature and humidity. This checks their durability, stability, and performance. It has many uses. It can test materials, electronics, auto parts, food, and drugs.

First, for constant temperature and humidity test chamber consists of which five systems?

The above systems include the control, refrigeration, heating, humidity, and air circulation systems. They divide into two areas: electrical and mechanical refrigeration.

1.Control system:

The control system is key to the test chamber. It determines its temperature rate, precision, and other important indicators. Most existing temperature and humidity test chamber controllers use PID control. A few use a mix of PID and fuzzy control.

2.Refrigeration system:

The refrigeration system is the key index of the test box. It tests constant temperature and humidity.

The refrigeration system is key to a test chamber. It must maintain a constant temperature and humidity. Its refrigeration is mainly mechanical. It uses vapor compression. This uses a compressor, condenser, throttling mechanism, and evaporator. For test boxes with constant temperature and humidity, there are two types of refrigeration: single-stage and two-stage. For temperatures below -40 ℃, we prefer using a two-stage system.

3.Heating system:

The heating system of the constant temperature and humidity test chamber is a high-power resistance line. The refrigeration system is simple. The chassis needs a higher heating rate. So, the heating system has a lot of power. The test box bottom plate also has a heater.

4.Humidity system:

The humidity system has two subsystems: humidification and dehumidification. It uses a steam humidification method. Directly inject low-pressure steam into the test space to humidify it. This humidification method is fast. It allows for precise control. It’s easy to achieve forced humidification in cooling.

There are two types of dehumidification: mechanical refrigeration dehumidification and desiccant dehumidification.

(1) Mechanical refrigeration dehumidification

Dehumidification cools the air below the dew point. This causes moisture to condense, reducing humidity.

(2) Dryer

Dehumidification uses air pumps to remove air from the test chamber. Then, it injects dry air. The recyclable dryer dries the moisture. This process repeats.

(3) At present, most comprehensive test chamber

Adopt the former dehumidification method. The latter dehumidification method can lower the dew point below 0 ℃. It’s suitable for special requirements, but it’s more expensive.

5.Air circulation system.

A constant temperature and humidity test chamber has an air circulation system. It usually has a centrifugal fan and a motor to drive it. It provides a constant temperature and humidity test chamber air circulation.

Second, the constant temperature and humidity test chamber has the principle of work

1.Constant temperature and humidity test chamber consists of two parts:

Temperature regulation (heating, cooling) and humidification. The rotating fan at the top of the box discharges air into it. This achieves gas circulation and balances the temperature and humidity. The box has built-in sensors to collect data. It sends this data to a temperature and humidity controller. This is a microprocessor that edits and processes the data. It issues control instructions to adjust the temperature and humidity. The air heater, the condenser tube, and the sink heater finish it.

2.The temperature adjustment of the equipment

The equipment adjusts its temperature with a built-in sensor. It collects data and sends it to a temperature controller (a microprocessor). The controller then connects to the air heater to raise the temperature. It adjusts the refrigeration solenoid valve to lower it. This controls the box’s temperature. The humidity sensor collects data through its body. A humidity controller (a microprocessor) adjusts the equipment. It either connects to the sink heater to raise humidity. Or, it adjusts the refrigeration valve to dehumidify. This controls the required humidity.

3. The constant temperature and humidity test chamber has multiple protections

It has a temperature system.And it can set the max safe temperature. It has an over-temperature protector. The rotating fan and automatic power-off can stop the air heating element. Reduce the humidification system with the humidification tank water level. Then, stop the power supply. The refrigeration system stops if the box temperature exceeds 40 °C or if humidity rises.

Third, the five main functions of constant temperature and humidity test chamber

1.High temperature test:

A programmable constant temperature and humidity test chamber can do high-temperature tests. It can reach 150 degrees Celsius. For higher temperatures, please contact us for a custom solution. It tests electronic products for high-temperature resistance. And it assesses the aging of the products in a high-temperature environment. It should not deform, dry out, or explode.

2.Low temperature test:

A programmable constant temperature and humidity test chamber can do low temperature tests. It can reach minus 70 degrees Celsius. For lower temperature tests, please contact us to customize it.

3.Humidity test:

A programmable constant temperature and humidity test chamber can test humidity. Its function is to simulate a humid climate. The standard humidity range is 20% to 98% RH.

4.Constant temperature and humidity test:

A programmable test chamber can run tests at a constant temperature and humidity. It can test high temperature and high humidity, and low temperature and low humidity. The most common test is the double 85 test. It sets the chamber to 85 ℃ and 85% humidity. This tests the reliability of the test samples.

5.Damp heat test:

A programmable constant temperature and humidity test chamber can do a damp heat test. It controls temperature and humidity. And it can also do an alternating damp heat test. It simulates the harsh spring, summer, autumn, and winter climates. This tests the product’s resistance to complex, abnormal climate changes. The product must resist damp heat after long exposure to it.

Fourth, the constant temperature and humidity test chamber compressor water problem

Some users report that, after a long time, the test chamber’s compressor will freeze or get blocked. It runs at a constant temperature and humidity. This is especially true in the humid spring in the south. The water vapor in the air can “wash” the building walls. At this time, the vapor can enter the compressor, which is very risky.

Ice blockage

When ice blocks the test box, the technician suggests this. First, fix the heating. Then, dry the pipeline with nitrogen. Finally, re-pump and inject the fluorine. If the ice blockage happens many times, the technician blames a bad evacuation or high fluorine in the water. In fact, the compressor inhalation of water causes many such failures.

Liner sealing is not tight

The constant temperature and humidity test chamber has a leaky liner. This allowed water from the air to enter the insulation. When the refrigerant leaked, the equipment failed. The compressor ran for a long time without stopping. This created negative pressure on the low-pressure side. The leak sucked in a lot of water. This caused repeated ice blockages in the compressor.

In this regard, I collated two solutions according to the technical staff:

Method one:

Use an electric stove or light bulb to carefully bake the compressor and evaporator. This is in a constant temperature and humidity test box. It will evaporate the water in the compressor and system. Then, use a vacuum pump to remove the air and water.

Method 2:

The high-pressure pipe and filter drier welded open. After idling the compressor for 2 to 3 times, the temperature will rise. This will evaporate and discharge water. Each time to four hours is appropriate, so as not to burn the compressor.

Constant temperature and humidity test chamber temperature and humidity display abnormality

1.If the constant temp and humidity chamber shows odd humidity, check the control humidifier’s over-temp protector. It should be set to 130 ℃. If it’s lower, the humidification may have failed due to low water temperature.

2. Next, check that the lab pipeline isn’t too long without cleaning. It may cause poor drainage. Then, check the wet cloth sink for water. Finally, check that the water inlet pipeline is clear and has no air.

3. Finally, check if the solid state relay is broken for humidity. It may be causing constant humidification. We can use a clamp-on ammeter to check the humidifier. It will show if the power is normal, and so on.

4.Turn off the total power supply of the constant temperature and humidity box. Open the drain valve under the humidification barrel to the parallel position. Drain all the water inside. Clean the internal dirt. Then, pull out the silicone pipeline and scrub it in water. After maintenance, reverse the removal steps to reassemble it. After finishing the device, you need to humidify the bucket below the drain valve. Close the valve by turning it perpendicular to the pipeline. Then, turn on the machine’s power to test the humidity.

Encounter overpressure alarm how to solve

First, we should confirm the ambient temperature. High temperature causes most of the overpressure. Confirmation is not due to the summer or lack of ventilation. The room temperature is too high. A general test chamber should have a temperature of 5 to 35 ℃. If the room’s temperature does not exceed the limit, check the equipment’s placement. It should not be too close to a wall or corner. This can cause poor heat dissipation and trigger an alarm.

Have you cleaned the constant temperature and humidity test chamber since you bought it? The refrigeration system is in the lower part of the machine. You can see the condensing fan, condenser, and other large parts. Check if dust has covered the condensing fan and condenser. If so, please clean it in time, as this tiny and unobtrusive dust is preventing it from dissipating heat. Cleaning is usually recommended once a month or quarterly. It can use a hoover or other aids. Note that the cleaning must be in the shutdown state.

Inspection: condenser poor heat dissipation causes are:

(1) The condenser is too dirty. (2) There is air in the refrigeration system. (3) The surrounding air does not flow. (4) The ambient temperature is too high. (5) There is an oil film on the condenser’s inner surface.

Processing results:

The test box at night refrigeration effect is normal, which excludes the above reasons in (1), (2), (3) and (5). The test box will no longer “jump” when moving it to other places. The constant temperature and humidity test chamber is too hot. It’s near the heat source from the condenser’s poor heat dissipation.

Solution:

Move the test chamber to a spot far from the heat and ventilation. This will eliminate the problem.

Fifth, do you do the daily maintenance of the test chamber? It must have constant temperature and humidity.

1. Maintenance

The maintenance of the constant temperature and humidity test box is basic. It is to check for loose, rusty, or missing screws, parts, and connections. Also, check for any depressions or cracks. Then, check the gasket, plug, and sealing strip for aging. Fix any issues promptly.

2. Compressor

The compressor plays a very important role for theconstant temperature and humidity test chamber, and it is expensive. Therefore, it is also important to do a good job of routine maintenance of the compressor. The work of the compressor requires stable voltage, otherwise it is easy to cause damage. So, install a voltage regulator on the test box. Frequent switching on and off of the compressor is not possible. Each switch interval should be more than 15 minutes.

 3.Motor and turntable reducer

If the motor and turntable reducer make noise, clear debris and oil them.

4.Circulatory system

Check for leaks or stains in the pump, pipeline, and drainage box in the circulatory system. Clean and maintain them as needed.

5.Not used for a long time

If you don’t use the constant temperature and humidity test box for an extended period, turn off the power. Then, clean and dry the box. Finally, store it in a dry, ventilated place away from direct sunlight. Shall not cover the equipment with plastic. This is to prevent dust from falling off, which may cause corrosion of parts. Even if not in use, it is best to energise the unit once a month for about an hour each time to protect the compressor.

6.Prevent parts from rusting

To prevent rust, wipe parts with oil. Use pure or distilled water, not tap water with impurities.

Sixth, consider a few things when doing constant temperature and humidity tests:

1. Test condition setting:

The test chamber’s temperature and humidity must be at the set values. This usually requires professional constant temperature and humidity test chambers or equipment.

2. Test standards:

Select appropriate test standards, like the ISO or relevant industry ones. This ensures the test is accurate and comparable.

3. Sample Preparation:

Prepare and install the sample per the test standard. This will ensure the sample’s surface is clean and undamaged. The installation method must match actual use conditions.

4. Data Recording:

During the test, record changes in temperature, humidity, and other parameters. Later analysis and comparison require them.

5. Test duration:

The product’s features and the test standard set the test’s duration. It must be long enough to collect and evaluate the data.

6. Safety considerations:

When testing at constant temperature and humidity, ensure the test equipment is safe. It must operate normally and meet safety standards. Also, protect the samples.

7. Result analysis:

After the test, we need to analyze the results. This will assess the product’s performance under different temperature and humidity conditions. It will help us improve and optimize the product.

Conclusion

A constant temperature and humidity test chamber is vital in modern industry. It precisely controls temperature and humidity. This supports product development and quality control. Using this constant temperature and humidity tester, enterprises can improve their product quality. They can also gain an edge in a tough market.

 

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