Study On Active Temperature Drift Compensation Circuit For MEMS Thermal Wind Sensor

In the 60s of the last century,MEMS technology has penetrated into every aspect of our lives,MEMS devices have advantages of small size,low power consumption,low cost and so on.Meanwhile,MEMS thermal anemometer came to stand on the stage of history,we can predict that MEMS thermal anemometer will replace the traditional anemometer in some specific areas,playing the role of meteorological monitoring.In this paper,we chose the silicon substrate as an example,analyzed the physical factors of temperature drift.Then the constant temperature difference circuit is put forward for constraint the environmental temperature drift.The main contents of this paper are as follows:Firstly,a brief introduction on MEMS and MEMS thermal anemometer was made,it includes the working mode of heat resistance,the detection principle of wind speed and direction and so on.Then some solutions on the MEMS temperature drift at home and abroad is provided.Then the structure of MEMS thermal sensor was discussed,and the reasons of the temperature drift on the MEMS thermal anemometer was analyzed,including the physical structure,the working mode of the heating resistance,the package form,the hardware circuit and so on.Meanwhile,the preliminary work of temperature drift in the laboratory is discussed.According to the reasons of the temperature drift on the MEMS thermal anemometer,the importance of constant temperature difference circuit to restrain the temperature drift is discussed.Then,the constant temperature difference circuit is proposed and its working principle is analyzed theoretically.Later a Pspice-model is founded for a heating resistance of the MEMS thermal anemometer,convenient for the overall simulation of the circuit with the wind sensor.Then circuit function simulation,power wave simulation,tolerance analysis of the constant temperature difference circuit,etc.are proceeded.At the last,a test about constant temperature difference circuit for constraint the temperature drift was made,meanwhile,some guidance on the circuit structures and parameters of various components was given.Then the function of constant temperature difference in temperature box was verified.When the circuit works in heat loss mode,the temperature drift was measured,the final result shows that the circuit can measure wind speed about 50m/s or so,and in the normal 0-35? ambient temperature,wind speed bias that caused by ambient temperature drift is about 1.75m/s,when in extreme ambient temperature of-20-0? or 35-50?,bias caused by ambient temperature is about 3.5m/s.