Evaluation of the WET sensor compared to time domain reflectometry

This paper concentrates on the experimental calibration of a rapid, non-destructive sensor to investigate the salinization process by measuring the dielectric properties of the soil to estimate both the soil water content (theta) and pore water electrical conductivity (sigma(p)) for different soil types. The proposed sensor depends on the frequency domain reflectometry (FDR) technique and is called the WET sensor. It estimates the dielectric permittivity (K-a) and bulk electrical conductivity (sigma(a)) of soil. Then, it utilizes both of them to estimate theta and sigma(p). The new sensor is compared to time domain reflectometry (TDR) measurements. Time domain reflectometry is a well established technique for K-a and sigma(a) measurements in soils. The study involves experimental measurements in the laboratory using five different soil types and a range of theta values. In each soil type, three different electrical conductivity solutions (sigma(w)) were used. The results revealed that the calibration coefficients of water content and the soil parameter are significantly dependent on the soil type and slightly affected by electrical conductivity of the moistening solution.