Study Of The Pulse Modulated Thermal Wind Sensor

In recent years, typhoons, drought, flood and other natural disasters happened every year caused a lot of losses to our country’s economy and people’s lives. How to detect changes in the environment with scientific method becomes crucial. Research of meteorological including wind speed and wind direction, becomes the focus of attention.In this thesis, the pulse modulated thermal wind sensor system, combined with the sensor head which was designed with MEMS technology is studied. A new control circuit and detection circuit are designed. The designed sensor can display and transfer the wind information including speed and direction at the same time ultimately. The system includes the pulse modulated control circuit, thermal temperature difference detection circuit, communication module, power module and signal processing module. The basic working principle of the control circuit and the detection circuit are analyzed and simulated, and some experiments are done to verify the circuit. The control circuit is based on the working principle of hysteresis comparator, can adjusts its heating pulse’s duty cycle according to the feedback voltage from the sensor head, i.e.change the heating power, the constant temperature difference control mode is realized. The total power consumption of the system is about 1200mW, which means that the system saves the power consumption effectively. When the speed of wind is less than 10m/s, the maximum wind speed error is less than 0.5m/s mostly, at lOm/s～20m/s, the maximum wind speed error is less than 1.1 m/s. When the wind speed is less than 10m/s, the wind angle error is large, the maximum angle error can reach ±15°, it may be related with the low heating power at low wind speed, where temperature gradient measured by the thermocouple is little. When the speed of wind is larger than lOm/s, the maximum wind angle error of the system is less than ± 3°mostly, meets the requirement.The power dissipation of the pulse modulated thermal wind sensor is low, which satisfies the need for energy conservation, so the pulse modulated thermal wind sensor has great prospect. The method of control circuit adjusting the heating power automatically is simple, which can be used in many other systems widely.