Design Of Double Heating Humidity Sensor And Its Calibration System

Controlling the measurement error of high-altitude humidity has always been a difficult task for high-altitude meterorology observation in China.In rainy and snowy environments,and after entering and leaving the cloud,water condensation on the surface of a humidity sensor,such as rain dew and crystals,will cause the humidity measurement data to be higher than the true value,which is called as wet errors.In order to improve the accuracy and response speed of high-altitude humidity measurement,it is necessary to use a dual heating humidity sensor for dehumidification.In this paper,not only a set of temperature and humidity sensors is designed,but also an equipment used to verify the temperature and humidity environment test chamber is proposed.This equipment,which is a multi-channel temperature and humidity inspection system,can be utilized to test whether the temperature and humidity environment test chamber meet the sounding sensor testing standard.Through a detailed analysis of the working characteristics of the dual-heating temperature sensor,we know that the most important part of improving the humidity measurement performance is to increase the rate of heating and heat dissipation of the humidity sensor.In this paper,computational fluid dynamics(CFD)method is used,using the computational fluid dynamics(CFD)method,steady-state analysis simulates three commonly used heating methods: insulating paint for nickel-chromium alloy wire,carbon fiber low-pressure heating sheet,and polyimide heating film attached to a thin PCB.The transient temperature analysis was used to simulate the characteristics of heating time and cooling time.When designing a multi-channel temperature and humidity inspection system,in order to eliminate the influence of temperature on the measurement of humidity,the humidity parameter should be based on absolute humidity or dew point instead of relative humidity.In this paper,the Goff-Gratch equation and the relative humidity conversion relationship and the BP neural network algorithm optimized by PSO are used to fit the temperature and absolute humidity field distribution fields in the environmental test equipment to verify whether the parameters are qualified.Through simulation and research,the heating time and cooling time of the dual heating humidity sensor with three heating modes of nickel-chromium alloy wire,carbon fiber low-pressure heating sheet,and polyimide heating film at different altitudes and 500 m W heating power were respectively solved.Measure the time of the cycle.Simulations show that heating with a carbon fiber low-pressure heating pad is the optimal method.The selected appraisal box was used as a temperature and humidity environment test equipment to verify the validity.The measured 60 groups of data were analyzed and calculated.The maximum absolute error of the temperature field was 0.07°C and the root mean square error was 0.041°C.The absolute humidity field The maximum absolute error is 0.1 g/L,and the root mean square error is 0.063 g/L.It can be concluded that the temperature field and absolute humidity field inside the device are evenly distributed and stable,which indicates that it can be used as a ground-based measuring device for dual heating temperature and humidity sensors.