1、 Working principle
The thermal expansion coefficient tester calculates the thermal expansion characteristics of a material by measuring its dimensional changes during temperature changes. The core principle is based on the thermal expansion effect of materials: when the temperature increases, the vibration of particles inside the material intensifies, the average spacing increases, resulting in volume or length expansion. The instrument captures real-time changes in sample length through high-precision displacement sensors, and combines temperature control modules to obtain temperature data. Finally, the thermal expansion coefficient (α) is calculated according to the formula α=(L-L ₀)/(L ₀× Δ T), where L ₀ is the initial length, L is the length after temperature change, and Δ T is the amount of temperature change.
2、 Core structure analysis
Displacement measurement system
Sensor type: using laser interferometer or inductive displacement sensor, with an accuracy of up to micrometer level. The laser interferometer calculates displacement by reflecting the optical path difference, while the inductive displacement meter detects displacement changes by using the relative motion between the iron core and the coil.
Function: Real time monitoring of sample length changes to ensure data accuracy.
Temperature control system
Heating element: resistance wire or molybdenum disilicide heater, combined with liquid nitrogen cooling system, to achieve wide temperature range control from room temperature to 1650 ℃.
Temperature control method: PID temperature controller combined with thermocouple feedback to ensure temperature uniformity (± 0.1 ℃) and avoid measurement errors caused by local overheating.
Sample support and driving mechanism
Push rod structure: The sample is placed in a heating furnace, and when it expands, the push rod is pushed to produce displacement. The sensor converts the displacement into an electrical signal.
Vertical/horizontal design: The vertical structure is suitable for samples that shrink more than expand (such as ceramics), avoiding separation between the sample and the bracket; Horizontal structures are suitable for conventional material testing.
Vacuum and Atmosphere Control System
Vacuum system: composed of a direct coupled pump and a diffusion pump, ensuring a pure measurement environment and preventing oxidation.
Atmosphere control: Supports inert gases (such as nitrogen, argon) or vacuum environments to meet the testing needs of different materials.
Data Analysis and Control System
Software function: Based on the Windows system analysis software, it realizes fully automatic measurement control, data recording, curve drawing, and thermal expansion coefficient calculation.
Safety protection: equipped with functions such as cooling water flow monitoring and four level interlock protection for furnace overheating, ensuring the safe operation of the equipment.
3、 Application and advantages
The thermal expansion coefficient tester is widely used in fields such as metals, ceramics, and polymer materials, and can measure parameters such as linear thermal expansion coefficient, glass transition temperature, and phase transition temperature. Its non-contact measurement, high-resolution, and absolute measurement methods (without calibration) significantly improve testing accuracy and efficiency, providing key data support for material development and quality control.