全自动称重式雨量计的研制及性能分析

为了精准刻画降雨过程特征，研制了一种具有野外复杂条件下普遍适用的全自动称重式雨量计，该仪器以STM32单片机为核心，利用A/D转换芯片对称重传感器的电压信号进行放大处理，获取分辨率为0.01 mm的分钟级别的降雨数据。试验结果表明，该雨量计测量标准差为0.02 mm/min，测量准确度最高为98.67%，说明该仪器监测精度高且适用范围广。称重式雨量计分辨率高，对微小雨滴反应灵敏，使得其监测结果较翻斗式雨量计大。此外，利用称重式雨量计在王东沟小流域进行野外自然降雨观测，发现该小流域自然降雨集中在5-9月，主要以次降雨量≤5 mm的降雨为主，而次降雨量为＞10~25 mm的降雨对降雨总量贡献最大。该仪器可以实时准确地监测降雨全过程，可为提高降雨监测技术的精准化和自动化水平提供参考。

Development and performance analysis of an automatic weighing rain gauge

Precipitation has widely been recognized as a fundamental component of the global water cycle. Accurate measurement of precipitation is very necessary for the main input into hydrological models. Hydraulic structures are then required to adequately design for efficient management of water resources. Several types of automatic rain gauges have been used in recent years, such as ultrasonic and laser rain gauges, but tipping-bucket rain gauges are still the common choice. Particularly, the tipping-bucket rain gauge can provide a better temporal resolution for the rainfall intensity. However, questions still remain on the accuracy of graphical representation for the actual rainfall. In this study, a real-time and automatic monitoring instrument was developed for the weighing rain gauge with high precision for precipitation. Three parts were composed of collector, weighing, measurement, and control subsystem. These subsystems were applied to multi-scenario conditions and performed well under the complex field. As such, the instrument was able to realize sample collection and measurement, data transmission and calculation, remote control, and diagnosis synchronously, compared with the traditional. The A/D conversion chip was utilized in the STM32 single-chip microcomputer to amplify the voltage signal of the weighing sensor. Subsequently, two important parameters of rainfall and rainfall intensity were achieved at a minute level with a resolution of 0.01 mm. Finally, a peristaltic pump was selected to verify the calibration of the developed instrument. The target intensities of rainfall were set as 0.02, 0.08, 0.17, 0.25, 0.50, 0.67, 0.83, 1.67, and 3.33 mm/min. The samples with the rainfall intensity of 0.83 mm/min were measured 30 times, and the rest were run five times. The results showed that the average rainfall intensity was 0.85 mm/min, where the histograms of target rainfall intensity presented a normal distribution, indicating higher precision of developed instrument than before. The best fitting linear regression was also represented by a slope with the R2 value close to 1. Additionally, the average error of the designed instrument was -1.32%, while the highest accuracy was 98.67%, and the relative error of less than 5% accounted for more than 85% of the total samples. The measured data of the developed instrument was also much larger than that of the tipping-bucket rain gauge under simulated rainfall conditions. The high resolution and sensitivity to light rain were contributed to the increase of effective rainfall rate and total rainfall. Finally, the performance of the developed instrument was verified under field conditions in the Wangdonggou watershed for one consecutive year. It was found that the annual rainfall was 522.80 mm, particularly concentrated from May to September. Correspondingly, the single rainfall less than 5 mm was the predominant contributor in natural precipitation, accounting for 74.11% of the total number of rainfall events, whereas, the single rainfall of 10-25 mm was the most important to total rainfall. Consequently, the self-designed instrument can widely be expected to automatically monitor the large variation of rainfall in most complex fields.