A walk-in constant temperature and humidity chamber is a large-scale experimental equipment used to simulate extreme environmental conditions such as high humidity, low temperature, or high temperature and high humidity, in order to test the moisture resistance of materials, products, or equipment. The experimental technical requirements should cover aspects such as environmental parameter control accuracy, uniformity, stability, safety protection, and operating standards to ensure the accuracy and reliability of test results. The following are detailed technical requirements:
1、 Requirements for controlling core environmental parameters
1. Temperature control
Scope: It usually needs to cover temperatures from -70 ℃ to+150 ℃ (depending on equipment specifications) to meet testing requirements such as low-temperature storage and high-temperature aging.
Accuracy:
Set value deviation: ≤± 0.5 ℃ (in steady state).
Temperature fluctuation: ≤± 0.3 ℃ (within 1 hour).
Uniformity:
Temperature difference between any two points in the studio: ≤± 1.5 ℃ (when unloaded).
When loaded (such as after placing the test sample): ≤± 2.0 ℃.
Gradient control: supports multi-stage temperature program settings (such as adjustable heating/cooling rate from 0.1 ℃/min to 10 ℃/min).
2. Humidity control
Scope: Typically ranging from 10% RH to 98% RH (some equipment can be extended to above 99% RH), meeting testing requirements such as dry, constant humidity, and high humidity.
Accuracy:
Set value deviation: ≤± 2% RH (steady-state).
Humidity fluctuation: ≤± 1.5% RH (within 1 hour).
Uniformity:
Humidity difference between any two points in the studio: ≤± 3% RH (when unloaded).
Under load: ≤± 5% RH.
Humidification/dehumidification rate:
Humidification rate: ≥ 5% RH/min (from 30% RH to 90% RH).
Dehumidification rate: ≥ 3% RH/min (reduced from 90% RH to 30% RH).
3. Cross control of temperature and humidity
High humidity and low temperature working conditions:
For example, when the temperature is+5 ℃ and the humidity is 95% RH, it is necessary to ensure that the condensed water is evenly distributed and does not damage the sample.
High temperature and high humidity working conditions:
For example, when the temperature is+60 ℃ and the humidity is 85% RH, it is necessary to prevent local overheating or humidity stratification.
Program control: Supports custom temperature and humidity curves (such as step wise humidity rise, constant temperature and humidity alternation, etc.).
2、 Measures to ensure uniformity of environmental parameters
1. Air circulation system
Wind speed control:
Wind speed in the studio: 0.1m/s to 0.5m/s (adjustable), to avoid direct blowing of samples that may cause local temperature and humidity abnormalities.
Use multi blade centrifugal fans or axial fans to ensure even distribution of airflow.
Diversion design:
The inner wall of the studio adopts a curved angle design to reduce dead corners of airflow.
Configure adjustable air deflectors to optimize airflow direction.
2. Layout of temperature and humidity sensors
Quantity and location:
Temperature sensors: at least 3 (1 each for the upper, middle, and lower layers), located near the sample placement area.
Humidity sensors: at least 2 (diagonally distributed), avoid proximity to humidification/dehumidification devices.
Calibration requirements:
Regularly calibrate sensors with standard temperature and humidity sources (such as precision dew point meters), and replace them if the deviation exceeds the allowable range.
3. Load impact compensation
Sample placement specifications:
The sample spacing should be ≥ 10cm to avoid obstructing the airflow.
Large volume samples need to reserve ventilation channels to prevent local temperature and humidity anomalies.
Dynamic compensation algorithm:
The equipment needs to be equipped with load compensation function, which automatically adjusts temperature and humidity control parameters according to the sample quantity and volume.
3、 Security protection and alarm function
1. Over temperature/over humidity protection
Level 1 alarm: When the temperature and humidity exceed the set value ± 3%, an audible and visual alarm will be triggered and data will be recorded.
Secondary protection: When the temperature and humidity exceed the safety threshold (such as temperature+80 ℃, humidity 99% RH), the heating/humidification power supply will be automatically cut off and emergency exhaust will be activated.
2. Condensed water management
Drainage system:
The bottom of the studio is equipped with inclined drainage channels, and condensed water is automatically discharged by gravity.
The drainage pipe needs to be equipped with a U-shaped bend to prevent external moisture from flowing back.
Anti water accumulation design:
The inner wall of the studio adopts anti condensation coating to reduce water droplet condensation.
Configure heating defrosting function (regularly activated under low temperature conditions).
3. Electrical safety
Insulation resistance:
The insulation resistance between the equipment casing and the grounding terminal is ≥ 1M Ω (tested at 500VDC).
Leakage protection:
Configure residual current circuit breaker (operating current ≤ 30mA, operating time ≤ 0.1s).
Explosion proof design:
Under high humidity conditions, electrical components need to be sealed with moisture-proof packaging (such as IP65 rating).
4、 Operating standards and experimental procedures
1. Preprocessing requirements
Sample pretreatment:
Before testing, the sample needs to be placed in a standard environment (temperature 23 ℃± 2 ℃, humidity 50% RH ± 5% RH) for 24 hours to relieve stress.
Equipment pre cooling/preheating:
After setting the target temperature and humidity, the equipment needs to run for at least 1 hour until it reaches steady state before placing the sample.
2. Experimental steps
Parameter settings:
Input parameters such as target temperature and humidity, duration, and number of cycles through touch screen or upper computer software.
Sample placement:
Distribute the samples evenly within the workspace to avoid obstructing the sensors or airflow channels.
Start experiment:
Close the cabin door and confirm good sealing, start the equipment and monitor real-time data.
Data recording:
The device automatically records temperature and humidity curves, or exports them to a computer through a data acquisition system.
Experiment completed:
After the experiment is completed, the equipment will automatically return to the standard environment (or manually set), take out the sample, and check for any changes in appearance.
3. Maintenance and Calibration
Daily maintenance:
Clean the interior of the studio every week and check if the drainage pipes are blocked.
Check the water level in the humidifier tank every month and replace it with purified water to prevent scaling.
Regular calibration:
The temperature and humidity sensors are calibrated by a third-party metrology institution every six months and a calibration certificate is issued.
Check the performance of key components such as refrigeration system pressure and heating element resistance every year.
5、 Typical application scenarios and cases
1. Moisture resistance test for electronic components
Test standards: IEC60068-2-78 (Constant Damp Heat), IEC60068-2-30 (Cyclic Damp Heat).
case
A certain mobile phone manufacturer tested the insulation performance of the motherboard in an environment with a temperature of+40 ℃ and a humidity of 90% RH for 72 hours, and then checked for short circuits or corrosion.
2. Moisture resistance test of building materials
Test standards: ASTMD2247 (Coating Water Resistance), GB/T1740 (Coating Moisture and Heat Resistance).
case
A certain paint company tested the foaming and peeling of exterior wall paint in an environment with a temperature of+50 ℃ and a humidity of 95% RH, and evaluated the weather resistance level after 500 hours.
3. Moisture resistance test for automotive components
Test standard: ISO16750-4 (Environmental conditions for electrical and electronic equipment of road vehicles).
case
A certain car company tested the sealing performance of onboard sensors in environments with alternating temperature changes from -40 ℃ to+85 ℃ and humidity changes from 10% RH to 95% RH. After 1000 hours, the functionality was checked for normal operation.
6、 Technological development trends
High precision control: using PID+fuzzy control algorithm to achieve dynamic compensation of temperature and humidity.
Energy saving design: Optimize the energy efficiency ratio (EER) of the refrigeration system to reduce operating costs.
Intelligence: Supports remote monitoring, fault diagnosis, and automatic calibration functions.
Modularization: Scalable multi factor coupling testing (such as temperature and humidity+vibration+salt spray).
summary
The moisture resistance performance of the walk-in constant temperature and humidity chamber requires strict environmental parameter control, uniformity assurance, safety protection, and operating standards to ensure the accuracy and repeatability of test results. Users should choose equipment of appropriate specifications according to their actual needs and regularly maintain and calibrate it to comply with international/domestic testing standards (such as IEC, ASTM, GB, etc.), providing reliable basis for product development and quality control.