3. The comprehensive test chamber is a high-end reliability test equipment that can simultaneously apply and accurately control the three environmental stresses of temperature, humidity and vibration in the same enclosed working space. Its core function is to simulate the multi-stress coupling conditions encountered by products during actual transportation, storage and use, such as cars suffering from road bumps when driving in high temperature and high humidity environments, and aerospace equipment experiencing mechanical vibration in temperature drastics. Compared with a single environmental factor test, the three-integrated test chamber can reveal the failure mechanism under the synergistic action of temperature, humidity and vibration, and expose potential defects that cannot be detected by a single test, which is a key means for product development and finalization, quality screening and reliability growth verification. By conducting tests under the three comprehensive conditions, the environmental adaptability of materials, components and the whole machine under the simultaneous action of multiple stresses can be evaluated in a short time, providing a scientific basis for product design improvement and quality control.
Principle
The working principle of the three-integrated test chamber is based on the coupling control of thermodynamics, fluid mechanics and mechanical vibration, and the three environmental stresses are applied simultaneously in the same space by integrating the temperature control system, humidity control system and vibration system. Its technical composition involves the coordinated operation of multiple subsystems, as well as interference suppression and precise synchronization between each system.
The temperature control system consists of three parts: heating, cooling and air circulation. The heating function adopts a nickel-chromium alloy fin heater, and the output power is adjusted by controlling the solid-state relay through the PID algorithm to achieve fast response and precise temperature control. In order to achieve a lower temperature, the refrigeration system generally adopts dual-machine overlapping refrigeration technology, including two independent refrigeration cycles of high temperature and low temperature stage, using environmentally friendly refrigeration working fluid, energy transfer through evaporative condenser, and efficiently transfer the heat in the working room. The temperature range typically covers -70°C to +150°C to meet the requirements of most test standards. The air circulation system adopts a large-capacity airflow organization design, forming a uniform flow field through centrifugal fans and air guide ducts to accelerate heat exchange and ensure the temperature uniformity of the working space, and the temperature uniformity can be controlled at ≤2°C and the fluctuation ≤±0.5°C under no-load conditions.
The humidity control system is realized through the synergistic work of steam humidification and refrigeration and dehumidification. The humidification function uses shallow slot steam humidification technology, which uses immersion heating tubes to generate pure steam, which is evenly mixed with the main airflow through the circulating air system. The dehumidification function is based on the principle of dew point condensation, when the air flows through the surface of the low-temperature evaporator, the water vapor condenses and precipitates, and the moisture content decreases. Humidity control typically ranges from 20% to 98% relative humidity, with uniformity within +2% to -3% relative humidity. The water for humidification should be deionized or purified water with low conductivity, and equipped with an automatic water replenishment and drainage system to prevent scale accumulation and microbial growth.
The vibration system is a core component that distinguishes it from ordinary environmental test chambers, usually using an electric shaker to generate controllable mechanical vibration. The shaker can output various modes such as sinusoidal vibration, random vibration, and shock vibration, and the frequency range covers DC to 3000 Hz. Key performance indicators include sinusoidal thrust, stochastic thrust, maximum acceleration, continuous displacement, etc., typical parameters such as sinusoidal thrust ≥ 2200 kN, maximum acceleration up to 950 meters per square second, and maximum load capacity of 300 kg. The shaker is dynamically sealed with the test chamber through the diaphragm interface, which not only ensures the effective transmission of vibration, but also maintains the airtightness of the temperature and humidity environment in the box.
The control system is the nerve center of the three comprehensive test chambers, and modern equipment generally adopts special integrated controllers to achieve deep integration of vibration and temperature and humidity control. The control system has the following core capabilities: test settings, parameter display and curve recording are completed on the same software interface; The timeline of vibration and temperature and humidity changes is accurately synchronized, which is convenient for the monitoring of comprehensive test status and the retrieval of historical data. Support multiple interface connection methods to increase the flexibility and adaptability of the device; Digital input/output ports are standard for controlling and monitoring external devices, enhancing the automation and intelligence of testing. The control system also provides data logging, storage, and export functions to meet data traceability and compliance requirements.
The box structure adopts a modular design, usually supporting various methods such as self-lifting, hydraulic lifting, and gantry lifting to meet the access needs of different sizes of shakers. The liner is made of SUS304 stainless steel, and all seams are continuously welded to form a sealing unit to prevent moisture migration. The outer box is made of high-quality steel plate electrostatic spraying, and the insulation layer is made of rigid polyurethane foam and glass fiber composite structure to ensure energy efficiency. The observation window is made of multi-layer hollow tempered glass, equipped with electric heating and frost protection device and interior lighting, which is convenient for real-time observation of the sample status.
Measurement method and measurement verification
3. The performance verification of the comprehensive test chamber should be systematically measured and measured according to national standards, referring to relevant standards such as GB/T 2423 series, IEC 60068-2 series and GJB 150A. The validation process should be conducted separately under no-load and typical load conditions to comprehensively evaluate the actual performance of the equipment.
Measurement of temperature performance includes temperature range, temperature deviation, temperature uniformity, and temperature fluctuations. Arrange at least nine test points in the workspace according to specifications, and record the temperature values of all points at regular intervals for at least 30 minutes after the temperature of the equipment stabilizes. Temperature deviation refers to the difference between the measured maximum temperature, minimum temperature and nominal temperature of each test point in a steady state. Temperature uniformity is obtained by calculating the average of the difference between the highest and lowest measured temperatures at all test points in each recording. Temperature fluctuations are expressed as half the difference between the highest and lowest temperatures recorded at the center point during the stabilization phase.
Measurement of humidity performance requires a precision dew point meter or calibrated hygrostor-capacitor sensor with multiple test points in the workspace to measure humidity deviation, uniformity, and fluctuation. The measurement results must be within the tolerances specified by the standard, and a humidity deviation ≤± 3% relative humidity is usually required.
Vibration performance is measured including frequency range, thrust capability, acceleration uniformity, and waveform distortion. The accelerometer is placed at the key position of the vibrating table to measure the vibration transmission characteristics under different frequencies and load conditions. Frequency response analysis determines the first-order resonant frequency and usable operating frequency range of the system. Thrust verification is calculated by measuring the maximum acceleration that can be achieved under a specified load.
Comprehensive performance verification is the core part of the evaluation of the three comprehensive test chambers, and it is necessary to measure the degree of mutual influence of each parameter under the condition of temperature, humidity and vibration applied at the same time. It focuses on the interference of vibration on temperature and humidity uniformity, the influence of temperature and humidity changes on vibration characteristics, and the accuracy of synchronous control of each system. The verification process should be based on IEC 60068-2-53 and other comprehensive test standards, and the full cycle of operation test should be carried out according to the preset test profile.
Measurement verification needs to be carried out in accordance with JJF 1101-2003 "Temperature and Humidity Calibration Specification for Environmental Test Equipment" and other relevant measurement regulations, and third-party calibration should be carried out once a year. The calibration cycle of the temperature sensor should support 6 months without calibration, and the measurement uncertainty should be controlled within 0.1°C. For devices that need to comply with pharmaceutical industry specifications, the data traceability system also needs to be verified to meet FDA 21 CFR Part 11 requirements for electronic signatures and audit trails.
Key factors that affect performance
3. The actual operating performance of the comprehensive test chamber is restricted by a variety of factors, which are directly related to the accuracy and reproducibility of the test results. The load characteristics are one of the important influencing factors, and the material, quality, volume and power of the test sample will affect the thermal equilibration process and vibration transfer characteristics in the chamber. For heated samples, if the spontaneous heat generation exceeds the equipment compensation capacity, it may result in temperature overshoot. The installation of the sample on the shaker directly affects the vibration transmission efficiency, and the improper number and position of the mounting points will lead to uneven acceleration distribution and affect the effectiveness of the test. When placing the sample, ensure that there is sufficient air gap with the box wall to maintain smooth airflow and avoid local temperature deviations.
The interface design between the shaker table and the box is a key link affecting the comprehensive performance. The diaphragm interface should not only ensure the effective transmission of vibration, but also maintain the tightness of the temperature and humidity environment in the box. The stiffness, mass, and damping characteristics of the interface directly affect the frequency response and available operating frequency range of the system. Improper interface design can lead to vibration energy loss, waveform distortion, or seal failure. The design accuracy of the lifting mechanism affects the positioning repeatability and operation convenience of the shaker, and different methods such as hydraulic lifting and gantry lifting have their own applicable scenarios.
The airflow organization directly affects the temperature and humidity uniformity and recovery rate. The high-capacity airflow system includes a robust air circulation motor that provides better airflow and improves controllability in the chamber. Better airflow minimizes temperature gradients and accelerates the rate of temperature change of the device under test. If the air duct design is not reasonable or the filter is clogged, it will lead to a short circuit in the airflow or a decrease in wind speed, which will significantly reduce the uniformity of temperature and humidity and the recovery rate. For testing under vibration conditions, the airflow organization also needs to consider the effect of vibration on the airflow distribution to avoid local eddy currents.
Environmental conditions have a significant impact on equipment performance. The temperature of the equipment installation environment should be controlled within the range of 5 to 35°C, the relative humidity should not exceed 85%, and good ventilation should be maintained. For water-cooled equipment, the stability of cooling water temperature and flow directly affects the refrigeration efficiency, and it is necessary to equip a cooling tower and ensure sufficient cooling water. The power supply quality cannot be ignored, and the voltage fluctuation of the three-phase five-wire power supply system should be within ±10%, and the total harmonic distortion should be controlled within an acceptable range.
The synchronization accuracy of the control system is the core factor affecting the success or failure of the three comprehensive tests. The timeline of vibration and temperature and humidity changes must be precisely synchronized to facilitate the monitoring of the comprehensive test status and the recall of historical data. If the synchronization accuracy of the control system is insufficient, it will lead to the disorder of the stress application sequence, and the actual working conditions cannot be truly simulated. Modern all-in-one controllers can effectively solve this problem by setting up experiments, displaying parameters, and recording curves all on the same software interface, ensuring a consistent timeline.
Defrost control strategies affect the equipment's ability to operate continuously in hot and humid conditions. Under low temperature and high humidity conditions, the surface of the evaporator is prone to frost, and the heat transfer efficiency gradually decreases as the frost layer thickens. The equipment should have intelligent defrosting function, judge the timing of defrosting through dew point logic, and use hot air bypass to achieve rapid defrosting, shorten the defrosting time and improve the efficiency of equipment use. The defrosting interval and duration directly affect the continuity of the test and are one of the important indicators to measure the technical level of the equipment.
Typical application areas
3. The application of comprehensive test chambers has expanded from early material resistance testing to product research and development, failure analysis, quality screening and other full-process fields. The automotive electronics industry is an important application field of this equipment, and the battery pack of new energy vehicles must withstand the ambient temperature of more than 40 °C and the relative humidity of more than 90% when driving at high speed in the south in summer, as well as the continuous vibration caused by road bumps. According to QC/T 413-2002 and QC/T 773-2006 and other standards, three comprehensive tests are carried out on automotive electrical equipment, radiators, electronic fans, etc., to verify their reliability in the real use environment. Automotive-grade electronic control units and sensors are subjected to a combination of temperature cycling from -40°C to +85°C and random vibrations to ensure stable operation under complex road conditions and climate change.
The aerospace field has higher requirements for the extreme environment simulation ability of the three comprehensive test chambers. Satellite components need to withstand severe vibrations during launch while simulating the low-temperature and vacuum environment of space to test their functional stability under multi-stress conditions. Avionics need to verify anti-interference in high-altitude, low-temperature and low-pressure environments, as well as vibration tolerance during aircraft takeoff and landing. According to the GJB 150A series standard, the airborne equipment is subjected to three comprehensive tests of temperature, humidity and vibration to ensure its mission reliability under severe working conditions. In this field, four comprehensive test chambers are also widely used, and low atmospheric pressure simulation functions are added on the basis of temperature, humidity, and vibration to test product performance in high-altitude and space environments.
The electronics and electrical industry uses three comprehensive test chambers to evaluate the reliability of components, printed circuit boards and complete machines under multi-stress conditions. A large number of engineering practices have shown that single environmental tests often miss fatal defects: only high-temperature testing may find material softening, but it cannot expose the fatigue cracking of the solder joints of the circuit board caused by moisture and vibration; Only vibration testing may detect structural looseness, but ignore the problem of intensified friction between plastic parts and metal parts after expansion at high temperatures. Moisture heat testing alone evaluates moisture resistance, but does not simulate vibration-accelerated corrosion during equipment operation. 3. The value of the comprehensive test is to reveal the synergistic failure mechanism of 1 plus 1 plus 1 greater than 3. For 5G base station equipment, it is necessary to simulate the long-term operating life under the combined action of outdoor temperature difference, humid and hot environment, and wind-loaded vibration.
The field of new energy involves photovoltaic modules undergoing comprehensive tests such as day and night temperature differences, humidity changes, and wind-loaded vibrations in outdoor service. According to the GB/T 2423 series standard, three comprehensive tests are carried out on photovoltaic backplane materials, junction boxes and inverters to evaluate their reliability throughout the life cycle. Critical components of wind turbines, such as blades, gearboxes, and control systems, need to be verified for structural integrity and functional stability under temperature changes, moisture intrusion, and continuous vibration.
In the field of materials science and advanced manufacturing, three comprehensive test chambers were used to study the interlayer bonding strength of composite materials, the thermal fatigue resistance of electronic packaging materials, and the aging behavior of polymer materials in humid and hot vibration environments. Through the three comprehensive tests, the performance attenuation data of materials under multi-stress coupling conditions can be obtained in a short time, which provides a basis for material selection and process optimization. Semiconductor devices and integrated circuits need to be tested in accordance with IEC 60068-2-53 and other standards to evaluate their reliability under complex working conditions.
In the field of rail transit, three comprehensive tests were carried out on the on-board electronic equipment, signaling system and traction control system to verify its reliability under the combined effect of temperature change, humidity attack and continuous vibration experienced in cross-regional operation. The field of industrial equipment involves automation control systems, instrumentation and mechanical equipment, and its adaptability and long-term stability in the complex environment of industrial sites need to be evaluated through three comprehensive tests.
Selection decision elements
3. As a high-value fixed asset, the selection of the comprehensive test chamber is a prudent decision that needs to comprehensively consider current needs and future development. First, it is necessary to clarify the test requirements and applicable standards, and determine the required temperature range, humidity range, vibration characteristics and comprehensive test profile according to the product use environment and relevant standards. Common test standards include GB/T 2423 series, IEC 60068-2 series, GJB 150A series, MIL-STD-810 series, etc. For specific industries, professional standards such as QC/T 413 are also considered. The essence of the selection decision is the matching process between test requirements and equipment capabilities, and the manufacturer can be entrusted to conduct sample pre-testing to verify the suitability of the equipment.
The determination of volume should be calculated based on the size, quantity and placement of the sample. The general principle is that the volume of the sample should not exceed one-third of the volume of the studio, and sufficient air clearance should be reserved to ensure smooth airflow. Common studio sizes include 500×600×750mm, 1000×1000×1000mm, 1000×2000×1000mm, and 2000×2000×2000mm and other specifications. For large or heavy samples, the actual bearing capacity of the shaker table and the size of the table should be confirmed to avoid degradation of vibration performance due to excessive load. For heated samples, it is also necessary to evaluate whether their power consumption exceeds the compensating capacity of the temperature and humidity control system.
The determination of temperature and humidity performance parameters covers the most severe conditions required for testing, taking into account appropriate margins. The temperature range typically requires -60°C to +150°C and the humidity range requires 20% to 98% relative humidity. The temperature uniformity should be ≤ 2°C, the temperature fluctuation should be ≤±0.5°C, and the humidity uniformity should be within the range of +2% to -3% relative humidity. The temperature rise and fall rate needs to meet the requirements of the specific test profile, with typical values ranging from 1.0 to 3.0 °C per minute and 0.7 to 1.0 °C per minute for cooling. For scenarios that require rapid temperature changes, a model with a higher temperature rise and fall rate should be selected.
The determination of vibration system parameters should be selected according to the vibration type, frequency range, acceleration and thrust required by the test. Key parameters include sinusoidal thrust, random thrust, frequency range, maximum acceleration, and maximum load capacity. The typical configuration provides a frequency range DC to 3000 Hz, a sinusoidal thrust ≥ 2200 kN, a maximum acceleration of 950 meters per square second, and a maximum load of 300 kg. The control accuracy and waveform distortion of the shaker table are also important considerations. For special test needs, a vibration system with higher thrust and a wider frequency range may be required.
The compatibility of the box structure with the shaker interface is a key part of the selection. The device should support compatible connections to the user's existing or newly purchased shakers, usually with diaphragm interfaces for dynamic sealing. The box lifting methods include self-lifting, hydraulic lifting, and gantry lifting, which need to be selected according to the laboratory space and operational convenience. The size and position of the viewing window should be convenient for observing the state of the sample, and the lighting system should ensure that there are no lighting blind spots in the working space.
The assessment of control system and data management capabilities is critical. Modern equipment should be equipped with a dedicated integrated controller to achieve deep integration of vibration and temperature and humidity control, ensuring that the timeline of the test process is accurately synchronized. The control system should support multi-stage program editing, with data recording, storage and export functions to meet the requirements of data traceability. For industries such as pharmaceuticals and aerospace, the system needs to be confirmed to meet FDA 21 CFR Part 11 specifications for electronic signatures and audit trails. The safety protection system needs to be perfected, including compressor overheating, overpressure, overtemperature, fan motor overheating, leakage protection, overall equipment underphase reversal, overload and short circuit protection, etc., forming multiple safety redundancy.
The selection of refrigeration method should comprehensively consider performance requirements and site conditions. Air-cooled equipment is easy to install, does not require additional water treatment facilities, and has low maintenance costs, making it suitable for small to medium-sized volumes and intermittent use scenarios. Water-cooled equipment has stable operation, low noise, and is suitable for high-load continuous operation scenarios, but it needs to be equipped with a cooling tower and ensure sufficient water supply. The refrigeration working fluid should be environmentally friendly, non-flammable, non-explosive, and have the potential to deplete ozone.
When making a final decision, the supplier's technical strength, manufacturing process, quality assurance system and after-sales service network coverage capabilities should be evaluated. Referring to similar user cases and third-party measurement reports, comprehensively consider factors such as equipment energy consumption, maintenance costs, and potential downtime losses, and select the most cost-effective solution. For special test needs, confirm whether the manufacturer supports non-standard customization to meet the requirements of specific test profiles.