基于Wenner和Schlumberger双组态融合的土壤电导率测量装置

    Measuring soil electrical conductivity using dual-array fusion of Wenner and Schlumberger

    • 摘要: 土壤电导率的准确、实时和原位获取可为农业生产精准管理提供有效的数据支撑,为提高传统电流-电压四端法测量精度,该研究基于电流-电压四端法3种测量组态,开展土壤电导率主要影响因素(土壤含水率、电极入土深度、土壤坚实度和土壤处理方式)对电流-电压四端法的3种测量组态测量精度影响的试验。结果表明,Wenner和Schlumberger两种测量组态可较好地适用于不同土壤环境条件。进一步以Wenner和Schlumberger两种测量组态所测土壤电导率值为输入量,基于BP神经网络构建了双组态融合的土壤电导率回归模型,并在此基础上设计了一种土壤电导率测量装置,该装置主要包括JESTON nano、STM32单片机数据采集模块、传感器、激励源及差分放大模块等组件。工作稳定性试验结果显示,该装置在不同土壤电导率梯度条件下测量数据的标准偏差均小于0.43 μS/mm;田间性能对比试验结果显示,该装置测量数据的均方根误差值为0.18 μS/mm,测量精度优于传统单独测量组态和市面常用土壤电导率测量仪,以上结果表明所研制的土壤电导率测量装置具有较好的工作稳定性和测量精度。该研究可为田间土壤信息的实时原位采集提供一种高精度的检测工具和技术手段。

       

      Abstract: Accurate, real-time, and in-situ acquisition of soil electrical conductivity can provide effective data support for the precise management of agricultural production. The current-voltage four-terminal approach as an invasive technology has considerable performance in the in-situ measurement of soil electrical conductivity on a large scale. This study aims to improve the accuracy of soil electrical conductivity measured by the traditional current-voltage four-terminal approach. A systematic analysis was made to determine the constant current source and electrode spacing in the three measurement arrays. The soil bin test was carried out to explore the influence of the main factors (soil moisture content, electrode embedded depth, soil compaction, and soil texture) on the measurement accuracy of three measurement arrays at different levels. The results showed that two measurement arrays of Wenner and Schlumberger were better applied to different soil environmental conditions. The measured values of soil electrical conductivity were further used as the inputs into the model. The regression model of soil electrical conductivity was constructed using the BP neural network. The R2 of the model fit was 0.99762 in the training set, and the RMSE of the model between the calculated and standard value was 0.12 μS/mm in the testing set, indicating the smaller than that of individual measurement. All RMSE values were smaller than those in the individual array measurements. The measurement device of dual-array fusion soil electrical conductivity was designed using a regression model. The components of the device included the touchable LCD display, electrode sockets, switches, differential amplifier module, constant current source module, power supply, STM32 microcontroller data acquisition module, JESTON nano, and sensor. The soil electrical conductivity was then optimized using the measured values. The working stability test showed that the standard deviation of measured data was less than 0.43 μS/mm under different soil electrical conductivity gradient conditions. The comparative field-site performance test showed that the absolute, relative error range, and RMSE of measured soil electrical conductivity were -2.1-1.8 μS/mm, -8.0%-5.8%, 0.18 μS/mm respectively. The RMSE of 0.18 μS/mm was smaller than that of the traditional individual measurement array and the commonly used soil conductivity meters in the market. The measurement device can be expected to rapidly and accurately detect the soil's electrical conductivity, indicating better working stability and higher accuracy. The finding can provide high-precision detection and technical means for the real-time in situ collection of soil information in the field.

       

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