As an important component to realize temperature detection, temperature sensors are widely used in scientific research, industry and agriculture, national defense and other departments. Platinum wire temperature sensor has a large detection temperature range, stable chemical properties and high detection accuracy. Platinum is the best raw material for manufacturing thermal resistance. Due to the influence of external working environment, the platinum wire temperature sensor installed in the intake port of an aircraft engine will change its resistance value, resulting in a certain error in its measurement accuracy. Therefore, it is of great significance to study the platinum wire temperature sensor under the actual working state to determine the failure mechanism of the sensor, improve the measurement accuracy and ensure flight safety. In this paper, platinum wire temperature sensor as the research object, through modeling software to establish the finite element model of platinum wire temperature sensor, and on the basis of ensuring the accuracy, according to the analysis needs, a certain simplification of the model. FLUNET software was used to simulate and analyze the flow field around the platinum wire, and the characteristics of fluid flow field, pressure distribution and velocity distribution were obtained. The flow field data obtained in the limit flow velocity state was transferred to the surface of the platinum wire through the fluid-structure coupling surface. The results show that the air velocity on the surface of platinum wire and the ridge is small, and the force on the surface of platinum wire is small when the air impinging on the platinum wire at the limit velocity state, and the air impinging is not the main cause of the failure of platinum wire.
The effect of annealing on the microstructure and properties of platinum wires used in standard platinum resistance thermometers was studied by various measurement techniques. The effect of annealing on the resistance/resistivity of Pt line was revealed by analyzing the relationship between dislocation density, nano-mechanical properties and resistance/resistivity. This work demonstrates a new approach to the problem of measuring the electrical resistance of fine platinum wires, which cannot be measured with conventional techniques. The results show that the main impurities in the initial Pt filament are graphite and some compounds composed of O, Ca, Mg, Si, Zn and N. PtO2 particles were formed near the Pt grain boundary during the annealing process. When the annealing time increases, PtO2 particles decompose into elements Pt and O2, and some of the compound impurities decompose or even disappear. Dislocation is the main factor affecting the mechanical properties of pt wires and the change of electrical resistance/resistivity. As the annealing time increases, the dislocation density of the platinum wire decreases, which further results in a decrease in the hardness and resistance/resistivity of the platinum wire.
