CALIBRATION OF TIME DOMAIN REFLECTOMETRY FOR WATER-CONTENT MEASUREMENT USING A COMPOSITE DIELECTRIC APPROACH
CALIBRATION OF TIME DOMAIN REFLECTOMETRY FOR WATER-CONTENT MEASUREMENT USING A COMPOSITE DIELECTRIC APPROACH
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DOI：
10.1029/90wr01238
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发表时间：
1990-10-01
影响因子：
5.4
通讯作者：
ATTINGER, W
中科院分区：
文献类型：
--
作者：
ROTH, K;SCHULIN, R;ATTINGER, W
在过去的十年中，时域反射仪（TDR）已经发展到用于测量土壤含水量的操作水平。由于它能够提供快速、精确和非破坏性的原位测量，它已成为中子散射方法的替代方法，特别是在现场条件下监测含水量。中子散射技术的一个主要缺点是，由于信号对含水量以外的因素的灵敏度相对较高，因此通常需要进行现场校准。本文提出了一种不受特定土壤条件限制的TDR方法的校准曲线。校准基于多布森等人（1985）的介电混合模型。测量的体积含水量和介电常数在11个不同的现场代表了广泛的土壤类型被用来确定模型的参数，通过加权非线性回归。采用优化校准曲线计算的含水量值的不确定度（均方根误差）估计不超过0.013 cm 3/cm 3。该值与热重法的精密度相当。根据灵敏度分析，确定可能必须校正TDR信号的温度依赖性以获得最佳精度。
Time domain reflectometry (TDR) has been developed to an operational level for the measurement of soil water content during the past decade. Because it is able to provide fast, precise and nondestructive in situ measurements, it has become an alternative to the neutron scattering method, in particular for monitoring water content under field conditions. One of the major disadvantages of the neutron scattering technique is that, due to the relatively high sensitivity of the signal to factors other than water content, site‐specific calibration is usually required. In this paper a calibration curve for the TDR method is presented which is not restricted to specific soil conditions. The calibration is based on the dielectric mixing model of Dobson et al. (1985). Measurements of volumetric water content and dielectric number at eleven different field sites representing a wide range of soil types were used to determine the parameter of the model by weighted nonlinear regression. The uncertainty (root mean square error) of water content values calculated with the optimized calibration curve was estimated not to exceed 0.013 cm3/cm3. This value is comparable to the precision of the thermogravimetric method. From a sensitivity analysis it was determined that the temperature dependence of the TDR signal may have to be corrected to obtain optimum accuracy.