| Meteorological monitoring plays a key role in many fields,such as agricultural production,industrial manufacturing,transportation,national defense and military.Wind speed and direction are a set of important meteorological parameters in meteorological monitoring,and wind sensor which can accurately measure the wind speed and direction is of great significance to human production and life.In recent years,compared with traditional wind sensor,MEMS thermal wind sensor,which has the advantages of small volume,high precision and low cost,is becoming a research hotspot and is moving towards market production.Our laboratory has many years of research experience in MEMS thermal sensor,and has a relatively mature scheme for its chip structure and packaging,the design of measurement and control circuit and reliability analysis.However,the sensor has the problem of high power consumption,which requires effective and reliable low power design;At the same time,there is also a lack of research on the application of the sensor under inclined condition and it is necessary to analyze,test and improve the sensor under this special condition.In addition,in order to realize the productization of the sensor,further reliability test is required and the problem of packaging reliability in the process of mass production is needed to be solve.The main research contents of this paper include:1.In the low-power design of the sensor,firstly,in the software of MCU,the design of low power consumption is presented and analyzed through module configuration and calculation program.Then a low-power heating control circuit combining software and hardware is proposed,where the heating voltage for constant-temperature-difference(CTD)mode in the hardware circuit is monitored and controlled by software program in MCU.However,the heating voltage curve of this scheme is not smooth,resulting in low measurement accuracy of wind speed.Furthermore,a pure hardware low-power heating control circuit is proposed,where there is no MCU and the automatic adjustment of heating voltage for CTD mode with the change of wind speed is realized.According to software simulation and test in the wind tunnel,the pure hardware low-power CTD heating control circuit is with good loop stability,and the whole sensor system can reduce power consumption up to 20% ～ 30% at wind speed of 0 ～ 30 m / s.2.In the application research of sensor under inclined condition,the sensor with aerodynamic cover is simulated and tested under inclined condition.The measurement error of wind speed in the test is much larger than that in the simulation,which results from large measurement error of wind speed when the sensor is in horizontal state with different wind direction.After solving this problem,measurement error of the wind speed and direction in the sensor under inclined condition is within the range of performance index that wind speed of ±(0.3m/s+0.05v)and wind direction of ±3°.3.In the reliability research of the sensor in product application,firstly,to verify the reliability of the sensor as a product working outdoors for a long time,the reliability test is carried out on several sensors under environmental stress.In addition,to solve the problem of packaging reliability from sensors in the process of mass production,the wire bonding scheme of PCB + FPC is proposed.Then it is applied to the packaging of products to improve the product qualification rate. |
