Design Of A High Precision Infrared Temperature Sensor System

Temperature is an important meteorological parameter in the agricultural field and is a basic information that needs to be monitored during crop growth.The accuracy of temperature measurement affects the yield and quality of crops.Due to factors such as solar radiation and long-wave radiation,there is a certain error between the surface temperature of the crop and the ambient temperature.Accurate measurement of the surface temperature of crops can effectively prevent sunburn,frostbite and can improve breeding programs.Infrared temperature measurement is the main way of non-contact temperature measurement.Its response speed is fast and the measurement range is wide.The temperature measurement does not need to touch the object to be tested,and it is more convenient to measure the surface temperature of crops.Infrared temperature measurement technology mainly includes infrared point temperature meter and infrared thermal imager.Compared with the infrared thermal imager,the infrared spot temperature meter has the characteristics of small volume and low cost,and has higher precision when performing single point measurement on the surface temperature of crops.However,the infrared thermometer is susceptible to the ambient temperature.Therefore,designing a high-precision infrared temperature sensor with small size,low cost and good environmental temperature compensation effect is of great significance in the agricultural meteorological field.This paper presents an infrared temperature measurement system for monitoring the surface temperature of crops.The system uses a Cortex-M3 ARM processor and an infrared probe consisted of a thermopile and a thermistor to measure the surface temperature of the crop in real time.In order to increase the accuracy of the measurement,a signal acquisition was acquired using a 24-bit low noise sigma-delta analog-to-digital converter AD7794.In order to control the object to be measured during the experiment,a temperature control circuit based on a peltier device is designed.The PID algorithm is used to control the working state of the peltier device,so as to accurately control the temperature of the object to be tested.A BP neural network algorithm optimized by genetic algorithm fits the corresponding relationship between the output voltage of the infrared probe and the target temperature at different ambient temperatures to compensate for the ambient temperature.A ZigBee module with CC2530 as the core is utilized to implement wireless networking.Transplanting the FreeRTOS real-time operating system to STM32 enhances the stability of system measurement and data transmission.In order to ease the use of monitoring personnel,this paper uses QT to develop the temperature monitoring PC software,and to display of the real-time temperature collected by each device and the entire farm's ambient temperature.The infrared temperature sensor designed in this paper can measure the target object from-10°C to 50°C.The root mean square error of the measurement was 0.07°C.The system can basically meet the temperature measurement needs of the farm and has great application potential in the agricultural meteorological field.