Design Of Thermal Wind Speed Sensor

Wind speed is an important meteorological elements It plays an important role in the development of social economy. At present, the wind speed is usually measured by mechanical measurement, ultrasonic measurement and thermal measurement methods. The threshold wind speed of the mechanical anemometer is usually in the range of 0.3 to 0.5 m / s, which makes it difficult to measure low wind speed. Ultrasonic wind speed sensor can achieve the accuracy of 0.01 m / s, but this sensor is larger and more expensive. Traditional thermal wind speed sensor has a high-sensitivity in the low wind speed range, but it is sensitive to environmental temperature. The temperature drift is one of the most important sources of error. In order to correct the temperature drift error of the sensor, the bridge circuit compensation is usually used and the linear formula compensation is carried out by the single chip microcomputer. However, it is difficult to obtain a better compensation effect for the sensor with a nonlinear temperature drift characteristic.Accurate measurement and temperature drift correction is a problem when the speed is below 0.3m / s.A design of thermal wind speed sensor is proposed in this paper. The sensor system consists of a sensor probe, signal acquisition circuit, constant power control circuit, temperature drift correction algorithm and master computer. The system uses a STM32 as the microprocessor chip, and a PT100 as the temperature measuring element , using a 24-bit high-precision AD7794 to carry on the analog-to-digital conversion. It also utilizes a PID algorithm and a pulse width modulation method to control the constant power heating of the sensor and constructs genetic algorithm as temperature drift correction algorithm of the sensor. Data collected by the system can be sent to the master computer through the serial port which is programmed by C# to display the data waveform and storage data.The computational fluid dynamics method is implemented to simulate the sensor probe, which provides the theoretical basis for the hardware design.Experimental results show that the temperature drift of the sensor is suppressed effectively. The full scale accuracy of the wind speed sensor is 5.19% when the ranges of environmental temperature and the wind speed are -20 ? 40 ? and 0.03 ?0.3m / s, respectively. It has a certain application potential in the field of low wind speed measurement.