基于交流“四端法”的土壤电导率在线实时检测系统

Soil Electrical Conductivity Online Real-time Detection System Based on Four-electrode Method

设计了一种土壤电导率在线实时检测系统,给出了交流“四端法”测量土壤电导率的全套设计方案,完成了信号源、交流恒流源、探针结构、传感器信号调理电路以及采集系统的设计,与直流“四端法”土壤电导率传感器相比,交流“四端法”测量土壤电导率方法具有更佳的检测性能。通过与国外同类产品对比研究,本测试系统性能达到了国外同类产品水平,具有更高的性价比。以北京地区土壤为测试样本,本系统检测量程：0-1 520μS/cm,检测误差：-2.2%-2.4%,动态响应时间：544 ms,测量带宽：1 MHz,满足土壤电导率实时在线测量的要求。

A soil electrical conductivity online real-time detection system was proposed. A full set of design scheme of AC method to measure conductivity was introduced, which included the design of a signal source, a stable AC current power supply circuit, probe, sensor signal conditioning circuit and acquisition system. The AC four-electrode method has a better detection performance compared with DC four-electrode method. The test system performance reached the same level compared with products from abroad and it had a more cost efficiency compared with the similar foreign products. Compared with Hydra Probe II sensor, the absolute error was -22.62 -29.41 p,S/cm, relative error was -2. 2% 2. 4%, the maximum relative error was 2.4% , the accuracy was the same. Compared with mercury thermometer, the temperature sensor had the absolute error of -0. 12 ~ 0.23~C, maximum relative error of 2.3% ,which can satisfy the accuracy of measurement. The soil in Beijing area was selected as test samples, the system＇ s measuring range was 0 - 1 520 μS/cm, monitoring error was - 2. 2% - 2.4% , the dynamic response time was 544 ms, the measurement bandwidth was 1 MHz, the performance can meet the measurement requirements, which can provide a high precision measuring tool for precise agroforestry.