| Meteorological monitoring guides industrial and agricultural production,transportation,national defense and other industries,and is closely related to people's lives.Wind speed and direction are essential key information in meteorological monitoring.The development and research of wind sensors is of great significance to the development of the national economy.Compared with traditional mechanical anemometers such as wind cups and vanes,MEMS thermal wind sensors have the advantages of small size,low maintenance cost,large range,and high accuracy.Our laboratory has been conducting research on MEMS thermal anemometers since 2000,and has accumulated a lot of results and experience in design,manufacturing,packaging,and circuit systems,and is currently committed to the commercialization of MEMS thermal anemometers.The current product adopts the control scheme of constant temperature difference,which can well restrain the temperature drift after tedious debugging.However,in the chip manufacturing process,it is not guaranteed that the parameters of the finished product are completely consistent,and there is inevitably a tolerance in the components,and it is difficult to debug the products one by one in mass production.At the same time,in terms of hardware circuit,software design,and packaging schemes,necessary optimizations have not been made to productization.The main research contents are as follows:a)In terms of stability,according to the principles of heat transfer and electricity,theoretical analysis of the zero-drift problem of the wind speed sensor without strict hardware temperature drift compensation is conducted.PSPICE software is used to model the heating resistor,and perform the overall circuit simulation.The results of the short-time variable temperature test and the outdoor long-time test are used to verify the conclusions of theoretical analysis and simulation,and a software compensation scheme for piecewise linear compensation is given.And through theoretical derivation and software simulation,the influence of the temperature drift of the external resistor on the sensor's performance is studied.b)In terms of reliability,a high-reliability sensor packaging solution that is conducive to mass production has been designed.The electro-magnetic compatibility is designed with hardware methods of protection,filtering circuits and software methods of watchdog timer and CRC data verification technology,and it has passed the certification of related tests.The system temperature control is designed to meet the needs of the sensor's low temperature operation,and the reliability of the work under the low temperature of-50 ? and the high temperature of +50 ? has been verified through environmental tests.And the conclusion that the performance of the sensor is almost unaffected by air humidity is verified through experiments.c)In terms of optimization of mass production,a software architecture that is convenient for mass testing and calibration and a fully functional Modbus-RTU communication protocol based on the RS-485 standard is designed.Based on the online flash programming function provided by C8051F410,the system can be debugged and calibrated through communication,which avoids the tediousness of programming the MCU.d)Test of the mass-produced sensors is conducted.The main performance characteristics of the sensor and the compensation's effect of zero-point drift are tested.The experimental results show that in the temperature range of-20 ??+50 ?,software compensation can reduce the error caused by the zeropoint temperature drift of the heat loss wind measurement from the maximum 2.32 m/s to 0.16 m/s;The hardware scheme of the full-bridge circuit is very effective in suppressing the zero-point temperature drift of the thermal temperature difference measurement,and the maximum error caused by the zeropoint drift in the X and Y directions does not exceed 0.5 m/s. |
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