Research Of Low-Power MEMS Thermal Wind Sensor

Great progress has been made in research and development of thermal wind sensor in recent years, and products have been widely used in many fields such as industrial and agricultural production, meteorological testing, environmental protection, biological medicine, automobile, and the greenhouse environment control. Before the advent of thermal wind speed sensor, mechanical sensing parts are mainly used to measure wind speed by people. When the techmology of making thermal wind speed sensor can be compatible with the integrated circuit production technology, not only the production cost can be reduced, and volume production can be realized, but also signal processing circuit and thermal wind speed sensor can be produced on the same chip, after that integrated intelligent thermal wind speed sensor can be possible.A low-power MEMS thermal wind speed sensor baed on the technology of through silicon via is introduced in this paper, with low thermal conductivity material glass as substrate of sensor and through-silicon-via as conductive path. This kind of sensor has advantages such as simple packaging, heat isolation and low-power. The wind speed ranges from 0 to 30m/s, satisfying the requirement for precision of 0.5m/s+5%, while the power of the system is less than 300m W. The main work is as follows:First of all, the research about reducing the power consumption of MEMS thermal wind speed sensor at home and abroad is analyzed in this paper. Three methods of reducing power consumption are summarized.Include:the optimization of the structure, choosing the substrate material with low thermal conductivity and temperature sensitive material with high performance, improving circuit control mode of the sensor. In this paper, the second and the third way are combined to reduce the power consumption of the system. By simulation the size of the sensor is optimized, sensor is made in the front of the glass substrate and the sensing structure is connected to the signal processing circuit by silicon via. Therefore, the heat loss caused by heat conduction can be reduced, and the sensitivity of the sensor can be improved. By the same time, the packaging process is simplified and the reliability of electric connection can be raised.Then, the power consumption of the hardware control circuit of thermal wind speed sensor which is based on silicon substrate or the ceramic substrate is analyzed, by which the program of simplifying the hardware control circuit can be determined. With the low-power sensor as the object, hardware control circuit of CP mode and CTD mode are respectively designed to analysis the relationship between the power and performance. Under CP mode, heating power consumption of the sensor is 11.52 mW and power consumption of hardware circuit is 153 mW. Under CTD mode, heating power consumption is from 101.56 m W to 101.56 mW and power consumption of hardware circuit is 92.85 mW.Finally, the sensor is tested to measure the power and the performance such as range of the sensor and stability, which of the two modes are compared. The sensor with CP mode has low and stable power consumption, while the sensitivity is low and serious temperature drift phenomenon exists; Dynamic range of the power consumption is large when sensor works under CTD mode, but the sensitivity is higher and to some extent the temperature drift can be controlled. Then problems are analyzed and solutions can be put forward in the late.