Definition
The temperature and humidity alternating test chamber is an environmental simulation device used to reproduce and precisely control temperature and humidity conditions in the laboratory, and realize the alternation of the two according to preset programs. It evaluates the weather resistance, reliability, and performance stability of materials or products by simulating the temperature and humidity cycling environment that products may experience during actual storage, transportation, or use.
Principle
The core working principle of the equipment is based on thermodynamic and hydrodynamic principles, and the environmental parameters are controlled by the integrated heating, cooling, humidification and dehumidification systems. The heating system usually uses resistance wire or electric heating pipe, the refrigeration system is mostly based on the compressor cooling cycle, the humidification system is often achieved by electrode humidification or steam humidification, and the dehumidification relies on the condensation of the refrigeration system or desiccant adsorption. The control system dynamically adjusts the output of each system through the PID algorithm according to the temperature and humidity data feedback from the sensor to achieve accurate programming of temperature and humidity.
Measurement method
The measurement of temperature and humidity parameters follows relevant national and international standards, such as GB/T 10586 and IEC 60068-2-78. Platinum resistance or thermocouple sensors are usually used for temperature measurement, and capacitive polymer thin film sensors are mostly used for humidity measurement. During measurement, the sensor is placed in the effective working space in the box, and its signal is converted into a standard electrical signal by a transmitter and recorded by the data acquisition system. Uniformity and fluctuation are the key evaluation indicators, which need to be verified by multi-point placement sensors. The uncertainty of the measurement results is evaluated according to the GUM.
Influencing factors
The accuracy of the test results is affected by multiple factors. Equipment factors include the uniformity of air flow in the workshop, the calibration status of the sensors, the thermal insulation of the cabinet, and the response speed of the control algorithms. The operating factors involve the placement of the specimen and the heat capacity of the load, and excessive load may affect the uniformity of the temperature field in the box. Environmental factors such as the laboratory's base temperature and supply voltage stability can also introduce interference. In addition, the conductivity of humidification water affects humidification efficiency and sensor measurements.
Applications
This equipment is widely used in fields where environmental adaptability verification of products or materials is required. In the electronics and electrical industry, it is used to test the reliability of circuit boards and components under high and low temperature cycles and humid heat conditions. In the automotive industry, it is used to verify the durability of components such as connectors and seals in simulated climatic environments. In the field of packaging materials, it is used to study the barrier properties and mechanical strength of materials under the alternation of temperature and humidity. In addition, it also plays an important role in quality inspection and R&D in building materials, aerospace, photovoltaic modules and other industries.
Selection considerations
The selection process is based on clear testing requirements and technical criteria. The primary parameter is the temperature and humidity range, which covers the limit conditions specified by the test standard with appropriate margins. The volume of the working room should be determined according to the size and quantity of the specimen, and ensure that the volume of the specimen does not exceed the specified proportion of the volume of the working room. The rate of temperature change is a key indicator, and it is necessary to distinguish between the average rate of the whole process and the linear temperature rise and fall rate. The number of steps, cycles and data recording ability of the control system should meet the requirements of test complexity. In addition, equipment energy efficiency, noise level, ease of maintenance, and the manufacturer's technical support and calibration services are also aspects to consider in long-term use.