Development Of Ultrasonic Rain Gauge Based On STM32

Rain gauge is a type of instruments used to measure rainfall over a period of time, widely used in meteorology, water conservancy and agricultural departments, which provides rainfall data for each department to forecast and study. At present, the accuracy and automation degree of rain gauge used in the field of domestic meteorology is low. And the price of foreign high-precision optical rain gauge is high, which is difficult to promote and popularize.In order to design a low cost, low power consumption and high-precision ultrasonic rain gauge, this paper optimizes the hardware and software algorithm of the traditional ultrasonic rain gauge. Hardware aspect, this paper chooses the low power consumption and high cost performance STM32 as the CPU. Ultrasonic measurement module consists of Ultrasonic launch and receiving, the part of launch drives Ultrasonic transducer by high voltage pulse, the part of receiving contains signal amplifying, filtering and shaping circuit. This design uses the PT100 to measure temperature, and chooses 24bit high-precision AD7794 to carry on AD conversion, temperature measurement precision can be up to ±0.05℃. It also carries on pressure compensation to rain gauge creatively, which make it suitable for more complex environment. Pressure module chooses BMP 180 to compose array structure, which reduce the system error caused by the creep of the sensor. This design can not only be displayed by VFD, but also be sent to the PC by serial port. Software algorithm compensation aspect, this paper uses L-M algorithm to achieve the curved surface fitting about ultrasonic velocity, temperature and pressure, which achieved the goal of temperature and pressure compensation. This paper developed supporting PC software based on Qt in order to let observers to use it easily.The range of ultrasonic rain gauge researched and developed by this paper is 0～500mm, and its frequency is adjustable. It is suitable used when the temperature range is 0～50℃ and the pressure range is 500～1100hPa. This design has low power consumption mode, so it can be used in the field for a long time. The performance testing of this design showed that rainfall error is±0.5 mm, which meets the requirement of the meteorological industry generally.