Design Of A Heated Twin Temperature Sensor Used In Meteorology Observation

Air temperature observation is essential for climate change research and weather forecast. The accuracy directly affects the upper atmosphere, the climate system analysis and forecast results. It is also particularly important for global warming monitoring. In radiosonde meteorological observation, the sensor should directly contact airflow. Water may cover the surface of the temperature sensor when in the environment of cloud or precipitation, which will affect the temperature measurement accuracy. In order to compromise the measurement error caused by the deposition of water on the temperature sensors, a heated twin temperature sensor is proposed in this paper. The changes of the measurement error and time constant under different wind velocities and precipitation intensities are measured by alternately heating the two temperature sensing devices. By fitting the corresponding function, the error correction and precipitation intensity measurement are achieved.To realize the functions of high-accuracy measurement, automatic collection and real-time processing, an ARM Cortex-M processor, STM32F103, is chosen here as the main control unit. PT1000 is utilized as the temperature sensor device, in combination with an A/D converter AD7793, which features low noise. A memory chip AT25256, a GPRS module and a heating control circuit are also implemented in the circuit. The system software design is based on FreeRTOS, a real-time embedded operating system. The software developed for this sensor includes temperature sensor signal conditioning, function fitting and calculation, communication and data storage. The difference of two squares is employed to realize the heating control. The L-M algorithm is used in fitting temperature step response curve to achieve the time constant calculation results. The block diagram is constructed in a virtual instrument (Labview), which is a PC software. The display and storage of the collected data are also realized in Labview.The test results show that under certain wind velocities and precipitation intensities, this design can reduce the error caused by water evaporation to below ± 0.1℃. The precipitation intensity measurement error is ±0.2 mm/min. Compared with traditional radiosonde temperature sensors, the heated twin temperature sensor features high precision and has the capability of error elimination. The measurement of precipitation intensity is also realized in this design. This sensor has a potential to find applications in weather stations and radiosonde.