Research On Error Correction Of Solar Radiation Of HC103M2 Sounding Humidity Sensor

In recent years,natural disasters such as floods,rainstorms,droughts,typhoons,and snowstorms have frequently occurred,which have caused huge losses to people's economic development.Therefore,high-precision meteorological detection is of great significance to disaster prevention and mitigation.The detection of air pressure,temperature,and wind of radiosondes has basically kept a good agreement with the accuracy of that of abroad.However,in terms of humidity measurement,there is still a certain gap between the accuracy of measurement at home and abroad.The problem of the deviation error of humidity sensor caused by solar radiation is obvious.Therefore,the simulation and experimental verification of the humidity sensor's deviation error caused by solar radiation are carried out in this paper.First of all,the deviation error of the humidity sensor is theoretically studied by using computational fluid dynamics(CFD)method.We selected the most widely used HC103M2 capacitive humidity sensor,and designed different protective shells.The radiation bias error is mainly due to the temperature increase caused by solar radiation on the humidity sensor.Therefore,the fluid dynamics method is used to study the temperature rise on the humidity sensor under solar radiation Pro/E was used to solid model,and the fluid dynamics method was used for simulation analysis.Based on which,the radiation temperature rise conditions under different intensity,pressure,flow speed as well as the shape,size and reflectivity of the protective shell were tudied.Secondly,in order to verify the accuracy of the simulation,a special temperature and humidity measurement circuit which includes a humidity sensor and two temperature sensors is designed.Since the HC103M2 is a capacitive humidity sensor,the measurement circuit uses a 555-multivibrator circuit to obtain humidity by measuring capacity.For the sake of studying the radiation temperature rise of humidity sensor,the circuit uses two high-precision temperature sensors(PT1000),one of which measures the temperature of the surface and the other measures the actual environment temperature.The measurement signal is collected by the AD7794 and the temperature difference is calculated through software processing.Finally,an experimental platform was set up to study the temperature rise of radiation.It uses the SS-150A full-spectrum ray simulation system to simulate solar radiation.The platform was designed with a vacuum tube to simulate the upper air environment.The characterization of different altitudes and airflow speed is simulated by changing the air pressure in the tube by the air pump whose pumping flow is adjusted by the flow regulator.During experiment,the temperature difference was recorded when the two temperature sensors tended to be stable over a certain period of time.It is found that the maximum relative humidity error is 3.3%,and the average error is 1.973%comparing the simulation results with the experimental results.This shows that using CFD method to study the solar radiation bias error is accurate and feasible.In view of the fact that the main factors affecting the solar radiation bias error of a given type of radiosonde are radiation intensity,atmospheric pressure and solar elevation angle,a BP neural network fusion algorithm is used to construct a radiation temperature prediction model whose maximum absolute error is about 0.2K.Then the relative humidity partial dry error is calculated to be ±1.3%combined with the Goff-Gratch formula.It can be seen that the prediction model has a high accuracy and can be used to correct solar radiation bias error.