1. Daily Maintenance
First, clean the interior of the box to remove any residual contaminants from the test (such as dust and sample debris) to prevent them from corroding the inner liner or contaminating subsequent test samples. After the box has completely cooled down, wipe the inner liner, shelves and inner walls with a dry soft cloth.
Second, clean the exterior of the box to prevent dust from blocking the ventilation openings and affecting heat dissipation. Especially around the ventilation openings, make sure there is no dust accumulation.
Thirdly, check whether the sealing strip of the box door is flat, free of cracks and deformation. Aging or damage to the sealing strip can lead to heat leakage and a decrease in temperature uniformity.
Fourth, empty the chamber: Emptying the chamber after use can prevent irrelevant items from being stored in the box for a long time, which may cause contamination or accidents.
2.Regular Maintenance
Please be sure to cut off the power supply before cleaning the heating element! Wait for the equipment to cool down completely. Open the rear cover plate and gently remove the dust on the surface of the electric heating tube and the air duct with a vacuum cleaner or a soft brush.
Check and clean the fan/impeller. Dust accumulation on the fan can cause dynamic balance imbalance, seriously affecting the uniformity of temperature. Therefore, after the power is cut off, it is necessary to check whether there is any abnormal noise from the fan motor bearings and use a vacuum cleaner to clean the accumulated dust on the fan blades.
Electrical components shall be inspected by professional equipment administrators for any loose, charred or rusted marks on the power lines, circuit breakers, contactors and other terminal blocks. Tighten the loose terminals and replace the damaged parts to ensure the safety and reliability of the electrical connection.
The accuracy of the temperature sensor can directly determine the success or failure of the test. It is recommended that every six months or once a year, a standard thermometer that has undergone metrological calibration be used to conduct multi-point comparison calibration of the working temperature range of the equipment. If deviations are detected, parameter corrections or sensor replacements should be made in the control system.
Clean the humidity system. If your device has a humidity function, you also need to clean the humidification water pan regularly, replace the wet cloth to prevent the growth of scale and algae, and use deionized water or purified water to reduce scale.
3. Long-term Maintenance after discontinuation
First, thoroughly clean the inside and outside of the box, and then completely cover the equipment with a dust cover.
Secondly, it is recommended to power on and run the equipment for half an hour to one hour without load once a month. This can remove the moisture inside the box, keep the electrical components active, prevent them from being damaged by moisture, and lubricate the mechanical parts.
Finally, during non-power-on periods, it is recommended to completely cut off the main power supply to ensure safety and save standby power consumption.
Please always keep in mind that safety comes first in the above operations. By implementing a systematic maintenance plan, you can extend the service life of the high-temperature oven, ensure the accuracy and repeatability of the test data, and reduce the frequency of equipment failures and maintenance costs.
The Guangdong Hongzhan Dust Test Chamber is primarily used to simulate natural sand and dust environments, testing the dust resistance of various products. In industries such as electronics, automotive, and aerospace, products may face challenges from sand and dust. If a product's dust resistance is inadequate, sand and dust particles can penetrate the equipment, leading to malfunctions, performance degradation, or even damage. Therefore, accurately assessing a product's dust resistance is crucial, and the Guangdong Hongzhan Dust Test Chamber provides a reliable testing platform for companies.
(1) Box structure: combination of robust and durable and sealing
The test chamber is constructed from high-quality stainless steel, which not only provides excellent corrosion resistance and protection against sand and dust erosion but also ensures good sealing to prevent sand and dust leakage, maintaining the stability of the testing environment. The interior is meticulously divided into functional areas such as the sample testing zone, sand and dust circulation duct, heating system, and control system, facilitating both operation and maintenance.
(2) Dust generation system: accurate simulation of dust environment
This is one of the core components of the test chamber. It consists of a sand and dust storage unit, a sand and dust conveying unit, and a sand and dust dispersion unit. The storage unit can hold sand and dust of various sizes and compositions as required by the test. The conveying unit delivers the sand and dust into the test chamber using either a screw conveyor or an air conveying method. The dispersion unit ensures that the conveyed sand and dust is evenly distributed in the air, creating a stable and suitable sand and dust environment for testing, ensuring that each sample is thoroughly tested under uniform conditions.
(3) Air circulation system: create stable dust airflow
The air circulation system consists of a fan, ducts, and an air filter. The fan provides the necessary power to ensure the air circulates within the test chamber. The ducts guide the airflow effectively, ensuring that the air passes through the sand and dust generation system and the sample testing area, allowing the sand and dust to fully contact the samples. The air filter effectively removes sand and dust particles from the circulating air, protecting the fan and other equipment from damage and extending their lifespan.
(4) Control system: intelligent and accurate operation core
The control system employs an advanced programmable logic controller (PLC) and a touch screen interface. Operators can easily set and monitor test parameters, such as temperature, humidity, dust concentration, and wind speed, via the touch screen. It also features automatic adjustment capabilities, allowing it to continuously monitor and precisely adjust the various parameters inside the test chamber according to preset values, ensuring that the testing environment always meets the required standards. Additionally, the control system includes fault alarm and protection functions, which can promptly issue warning signals and take protective measures in case of any abnormal conditions, ensuring the safety of both equipment and personnel.
(5) Complete workflow: efficient and rigorous testing process
During the preparation phase, operators select appropriate sand and dust particles based on the test requirements and place them in the storage device. They then clean and inspect the test chamber and properly position the samples within the testing area. Once the test chamber is activated, the sand and dust generation system begins to operate, conveying and dispersing the sand and dust into the air. The air circulation system ensures a stable flow of sand and dust air. The control system continuously monitors and adjusts various parameters to maintain a stable test environment. During the sample testing phase, the test chamber operates according to the set schedule
When operating a constant temperature and humidity test chamber, it is important to be aware of potential issues during the process and ensure proper operation. Improper handling can easily lead to equipment malfunctions. However, over time, some faults will inevitably occur. In this article, we will discuss several common faults and their solutions.
Fault: If the temperature does not reach the set value during high-temperature testing, the first step is to check the electrical system and troubleshoot each component. If the temperature in the constant temperature and humidity test chamber rises too slowly, check the air circulation system to ensure the adjustment damper is functioning properly. If the temperature rises too quickly, adjust the PID settings. If the temperature rises too quickly and triggers the over-temperature protection, the controller may be faulty; in this case, replace the control panel or solid-state relay.
Fault: If the constant temperature and humidity test chamber fails to meet the low-temperature test requirements, investigate whether the temperature drops very slowly or if it stabilizes at a certain point before rising again. If the temperature drops very slowly, check if the chamber was dried before the low-temperature test to maintain dryness. Ensure the samples are not placed too densely to prevent inadequate air circulation. After ruling out these issues, consider whether the refrigeration system is malfunctioning; in such cases, seek professional repair from the manufacturer.
Fault: If the constant temperature and humidity test chamber malfunctions during operation, with the control panel displaying a fault message and an audio alarm, the operator can refer to the troubleshooting section of the equipment's user manual to identify the type of fault. Professional maintenance personnel should then perform the necessary repairs to ensure the test proceeds smoothly. Other environmental experimental equipment will have other conditions in use, which need to be dealt with according to the current situation.
Foreword
The purpose of this test method is to provide a standardized procedure for evaluating the resistance of small electrotechnical products (primarily non-hermetic components) by high and low temperature and humid environmental test chamber.
Scope
This test method applies to accelerated damp heat testing of small electrotechnical products.
Limitations
This method is not suitable to verify external effects for specimens, such as corrosion or deformation.
Test Procedure
1. Pre-Test Inspection
Specimens shall undergo visual, dimensional, and functional inspections as specified in the relevant standards.
2. Specimen Placement
Specimens shall be placed in the test chamber under laboratory conditions of temperature, relative humidity, and atmospheric pressure.
3.Bias Voltage Application (if applicable)
If bias voltage is required by the relevant standard, it shall be applied only after the specimen has reached thermal and humidity equilibrium.
4. Temperature and Humidity Ramp-Up
The temperature shall be raised to the specified value. During this period, air in the chamber shall be displaced by steam.
Temperature and relative humidity must not exceed specified limits.
No condensation shall form on the specimen.
Stabilization of temperature and humidity shall be achieved within 1.5 hours. If the test duration exceeds 48 hours and stabilization cannot be completed within 1.5 hours, it shall be achieved within 3.0 hours.
5. Test Execution
Maintain temperature, humidity, and pressure at specified levels as per the relevant standard.
The test duration begins once steady-state conditions are reached.
6. Post-Test Recovery
After the specified test duration, chamber conditions shall be restored to standard atmospheric conditions (1–4 hours).
Temperature and humidity must not exceed specified limits during recovery (natural cooling is permitted).
Specimens shall be allowed to fully stabilize before further handling.
7. In-Test Measurements (if required)
Electrical or mechanical inspections during the test shall be performed without altering test conditions.
No specimen shall be removed from the chamber before recovery.
8. Post-Test Inspection
After recovery (2–24 hours under standard conditions), specimens shall undergo visual, dimensional, and functional inspections per the relevant standard.
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Test Conditions
Unless otherwise specified, test conditions consist of temperature and duration combinations as listed in Table 1.
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Test Setup
1. Chamber Requirements
A temperature sensor shall monitor chamber temperature.
Chamber air shall be purged with water vapor before testing.
Condensate must not drip onto specimens.
2. Chamber Materials
Chamber walls shall not degrade vapor quality or induce specimen corrosion.
3. Temperature Uniformity
Total tolerance (spatial variation, fluctuation, and measurement error): ±2°C.
To maintain relative humidity tolerance (±5%), temperature differences between any two points in the chamber shall be minimized (≤1.5°C), even during ramp-up/down.
4. Specimen Placement
Specimens must not obstruct vapor flow.
Direct radiant heat exposure is prohibited.
If fixtures are used, their thermal conductivity and heat capacity shall be minimized to avoid affecting test conditions.
Fixture materials must not cause contamination or corrosion.
3. Water Quality
Use distilled or deionized water with:
Resistivity ≥0.5 MΩ·cm at 23°C.
pH 6.0–7.2 at 23°C.
Chamber humidifiers shall be cleaned by scrubbing before water introduction.
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Additional Information
Table 2 provides saturated steam temperatures corresponding to dry temperatures (100–123°C).
Schematic diagrams of single-container and double-container test equipment are shown in Figures 1 and 2.
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Table 1: Test Severity
| Temp. (°C) | RH (%) | Duration (h, -0/+2) |
temperature
relative humidity
Time (hours, -0/+2)
±2℃
±5%
Ⅰ
Ⅱ
Ⅲ
110
85
96
192
408
120
85
48
96
192
130
85
24
48
96
Note: Vapor pressure at 110°C, 120°C, and 130°C shall be 0.12 MPa, 0.17 MPa, and 0.22 MPa, respectively.
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Table 2: Saturated Steam Temperature vs. Relative Humidity
(Dry temperature range: 100–123°C)
Saturation Temp(℃)
Relative
Humidity(%RH)
100%
95%
90%
85%
80%
75%
70%
65%
60%
55%
50%
Dry Temp (℃)
100
100.0
98.6
97.1
95.5
93.9
92.1
90.3
88.4
86.3
84.1
81.7
101
101.0
99.6
98.1
96.5
94.8
93.1
91.2
89.3
87.2
85.0
82.6
102
102.0
100.6
99.0
97.5
95.8
94.0
92.2
90.2
88.1
85.9
83.5
103
103.0
101.5
100.0
98.4
96.8
95.0
93.1
92.1
89.0
86.8
84.3
104
104.0
102.5
101.0
99.4
97.7
95.9
94.1
92.1
90.0
87.7
85.2
105
105.0
103.5
102.0
100.4
98.7
96.9
95.0
93.0
90.9
88.6
86.1
106
106.0
104.5
103.0
101.3
99.6
97.8
96.0
93.9
91.8
89.5
87.0
107
107.0
105.5
103.9
102.3
100.6
98.8
96.9
94.9
92.7
90.4
87.9
108
108.0
106.5
104.9
103.3
101.6
99.8
97.8
95.8
93.6
91.3
88.8
109
109.0
107.5
105.9
104.3
102.5
100.7
98.8
96.7
94.5
92.2
89.7
110
110.0
108.5
106.9
105.2
103.5
101.7
99.7
97.7
95.5
93.1
90.6
(Additional columns for %RH and saturated temp. would follow as per original table.)
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Key Terms Clarified:
"Unpressurized saturated vapor": High-humidity environment without external pressure application.
"Steady-state": Constant conditions maintained throughout the test.
Refrigeration System
The refrigeration system is one of the critical components of a comprehensive test chamber. Generally, refrigeration methods include mechanical refrigeration and auxiliary liquid nitrogen refrigeration. Mechanical refrigeration employs a vapor compression cycle, primarily consisting of a compressor, condenser, throttle mechanism, and evaporator. If the required low temperature reaches -55°C, single-stage refrigeration is insufficient. Therefore, Labcompanion's constant temperature and humidity chambers typically use a cascade refrigeration system. The refrigeration system is divided into two parts: the high-temperature section and the low-temperature section, each of which is a relatively independent refrigeration system. In the high-temperature section, the refrigerant evaporates and absorbs heat from the low-temperature section's refrigerant, causing it to vaporize. In the low-temperature section, the refrigerant evaporates and absorbs heat from the air inside the chamber to achieve cooling. The high-temperature and low-temperature sections are connected by an evaporative condenser, which serves as the condenser for the high-temperature section and the evaporator for the low-temperature section.
Heating System
The heating system of the test chamber is relatively simple compared to the refrigeration system. It mainly consists of high-power resistance wires. Due to the high heating rate required by the test chamber, the heating system is designed with significant power, and heaters are also installed on the chamber's base plate.
Control System
The control system is the core of the comprehensive test chamber, determining critical indicators such as heating rate and precision. Most modern test chambers use PID controllers, while a few employ a combination of PID and fuzzy control. Since the control system is primarily based on software, it generally operates without issues during use.
Humidity System
The humidity system is divided into two subsystems: humidification and dehumidification. Humidification is typically achieved through steam injection, where low-pressure steam is directly introduced into the test space. This method offers strong humidification capacity, rapid response, and precise control, especially during cooling processes where forced humidification is necessary.
Dehumidification can be achieved through two methods: mechanical refrigeration and desiccant dehumidification. Mechanical refrigeration dehumidification works by cooling the air below its dew point, causing excess moisture to condense and thus reducing humidity. Desiccant dehumidification involves pumping air out of the chamber, injecting dry air, and recycling the moist air through a desiccant for drying before reintroducing it into the chamber. Most comprehensive test chambers use the former method, while the latter is reserved for specialized applications requiring dew points below 0°C, albeit at a higher cost.
Sensors
Sensors primarily include temperature and humidity sensors. Platinum resistance thermometers and thermocouples are commonly used for temperature measurement. Humidity measurement methods include the dry-wet bulb thermometer and solid-state electronic sensors. Due to the lower accuracy of the dry-wet bulb method, solid-state sensors are increasingly replacing it in modern constant temperature and humidity chambers.
Air Circulation System
The air circulation system typically consists of a centrifugal fan and a motor that drives it. This system ensures the continuous circulation of air within the test chamber, maintaining uniform temperature and humidity distribution.
The High and Low Temperature Humid Test Chambers is the main equipment in temperature and humidity environment testing, mainly used for evaluating the temperature and humidity tolerance of products, so as to ensure that our products can work and operate normally under any environmental conditions. However, if the temperature uniformity exceeds the allowable deviation range during environmental testing in the Chambers, the data obtained from the test is unreliable and cannot be used as the ultimate tolerance for high and low temperature testing of materials. So what are the reasons that can cause temperature uniformity to exceed the allowable deviation range?
1. The differences test objects in the High and Low Temperature Humid Test Chamber: If test samples that to a great extent affect the overall camber’s internal heat convection, it will inevitably affect the uniformity of internal sample’s temperature. For example, if LED lighting products are test, the products themselves emit light and heat, becoming a thermal load, which will has a significant impact on temperature uniformity.
2. The volume of the tested object: If the volume of the test object is too large, or the placing position in the chamber is inappropriate, it will obstruct the air convection inside and also cause significant temperature uniformity deviation. For Placing the test product next to the air duct seriously affects the circulation of air, and of course, the uniformity of temperature will be greatly affected.
3. The internal structure design of the chamber: This aspect is mainly reflected in sheet metal design and processing, such as the design of air ducts, the placement of heating pipes, and the size of fan power. All of these will affect the temperature uniformity inside the camber.
4. Design of the camber’s inner wall: Due to the different structures about the inner wall of the test chamber, the temperature of the inner wall will also be uneven, which will affect the heat convection inside the working chamber and cause deviation in the internal temperature uniformity.
5. The six sides of the camber have uneven heat dissipation: Due to the different heat transfer coefficients on the front, back, left, right, top, and bottom surfaces of the camber’s wall, some sides have threading holes, others have testing holes, etc., which will cause local heat dissipation and transfer, resulting in uneven temperature distribution of the camber and uneven radiative convective heat transfer on the wall, final affecting temperature uniformity.
6. The leakproofness of camber’s door: The sealing of the camber and door is not strict, for example, the sealing strip is not customized and has seams between door and wall, the door will leaks the air, which is going to affects the temperature uniformity of the hole camber.
In summary, those may the culprit affected the temperature uniformity inside the test chamber, we suggest that you can investigate from these aspects one by one, which will surely solve your confusion and difficulties.
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