Långtidstestapparat för volframfilament

Sammanfattning

This bachelor’s thesis aimed to develop an automated measurement system to monitor the thermal expansion of tungsten filaments used in electron accelerator applications. The goal was to replace a manual and time-consuming measurement process with a more reliable and efficient solution. The project was carried out in collaboration with Electron Crosslinking AB. To achieve this, a mechanical test rig was constructed, allowing the tungsten filament to be mounted under controlled heating conditions. A Linear Variable Differential Transformer (LVDT) was used to measure the filament’s length change during thermal cycling. The signal from the sensor was processed using a high-resolution 18-bit analog-to-digital converter and recorded by a Raspberry Pi. Custom Python-based software was developed to handle real-time logging, visualization, and automated analysis of the measurement data. A calibration method based on a cubic spline model was implemented to improve accuracy and enable reliable conversion from voltage to physical displacement. The system successfully captured the filament’s expansion behaviour over multiple test cycles. The results showed that the static measurement drift was minimal and that the measurement accuracy remained within the targeted ±0.1 mm. The software generated automated reports including graphical output, raw data, anda summary protocol for each test. In conclusion, the developed system provides a robust, repeatable, and userfriendly solution for long-term thermal expansion testing of filaments. It significantly reduces manual labor while improving data quality and analysis reliability.