Development and testing of a high-precision static calibration device for aviation thin-film thermocouples

This study aims to develop a novel calibration device to address the challenges of inadequate temperature field uniformity, significant temperature fluctuation, and less reliability in existing static calibration devices for thin-film thermocouples. In the beginning, a multi-zone high-temperature furnace and the reference end thermostat were designed separately utilizing the three-zone temperature control method and metal block heating together with air-cooled cycle. The finite element analysis method was used to simulate the temperature fields in both the working area of the reference end thermostat and the furnace barrel of a multi-zone high-temperature furnace. The working area's temperature field environment was simulated and analyzed, which led to determining optimal partition length and heating power ratio of the multi-zone furnace heating wire. Finally, the temperature field in the multi-zone high-temperature furnace and the reference end thermostat were analyzed. The results demonstrated that the multi-zone high-temperature furnace significantly outperformed the conventional single-zone furnace. The uniform temperature field's length reached 80 mm, with an axial temperature gradient below the 0.4 ℃/10 mm required by the national regulations. Additionally, the reference end thermostat maintained a temperature fluctuation within 0.25 ℃/10 min, which can meet the calibration requirements.