| Special projects about civil airplane has two technical requirements.Thin film thermocouples used under such circumstances should endure about 1000℃.And the response time should be no more than 50us.According to the requirements above,Pt and Pt Rh were chosen as the thermoelectric function metal.The thermocouples were built on the substrate composed of Al2O3.A series of experiments about dynamic and static testing has been done.Firstly,according to the demand of thin film thermocouple’s testing environment,thin film thermocouples used for static and dynamic testing have been designed separately.The fabrication of thin film thermocouples is done with the help of MEMS technology.Then,the static testing platform of thin film thermocouple has been built.The system can get rid of the disturbance of compensating wire by making thin film thermocouple suspended upon the furnace block.The output of thin film thermocouple is almost same with that of standard thermocouple under repeated temperature changes.The fluctuation range is among?0.05m V.Thin film thermocouples can measure the temperature accurately and the result can be done repeatedly.The result meets the technical targets well.Finally,the dynamic testing platform of thin film thermocouple has been built.The output of thin film thermocouple and optoelectronic device have been collected synchronously.The time when laser starts contacting thin film thermocouple can be obtained.The pre response time is about 5us and the post response time is about 25us.Thin film thermocouple has fast response ability.In order to know the influence of PI,contrasting tests have been done.The results show that PI cannot influence the response time.PI effects the maximum output voltage.The output voltage changed from 6m V to 6.5m V,which means the temperature changed from 550℃to 580℃.Some other factors which may influence the response time also have been tested.The power factor of the laser has been set to 0.3,0.6 and 0.9 to test whether pulsed energy will influence the dynamic response.It influences the maximum output voltage directly.Response time has nothing to do with pulsed energy.The response time of 500nm thin film thermocouple is shorter than that of 1000nm.Finally,the technical target of the project is completed. |
