FDS土壤水分传感器的两步标定法

在有机溶液、砂土和基质(泥炭、蛭石、珍珠岩质量比4.5:4.5:1.0)中对基于频域(FD)原理的FDS系列水分传感器进行了测试,并根据实验结果对其阻抗特性、一致性和测量精度进行了分析。传感器的标定工作分2步进行,首先利用有机溶液建立传感器输出电压信号V与介电常数ε的关系,然后通过Topp公式间接得出传感器输出信号与土壤含水率之间的关系。在砂土和基质中的实验结果表明,采用两步标定法标定后,FDS系列传感器测量得到的砂土和基质含水率与烘干法得到的含水率的相关系数分别为0.90和0.95,其输出电压与ML2型传感器输出电压的相关系数>0.99,表明该标定方法能够满足测量精度要求。

Two-step calibration of the FDS soil water content sensor

The FD(Frequency Domain) technique,is used to measure soil water content(WC) based on the dielectric theory.The objective of this paper is to evaluate a two-step calibration procedure for a prototype FD sensor named FDS.The testing media include organic liquid,soil and substrate.The output voltage of the sensor is related to soil permittivity,and soil water content is then obtained from Topp equation that reflects the general relationship between permittivity and soil water content.The experimental results demonstrated that the data from the two-stage calibration agreed reasonably well with the results from the oven-dry method and the ML2 soil water content sensor.