β Scribed by W. K. P. Loon; E. Perfect; P. H. Groenevelt; B. D. Kay
No coin nor oath required. For personal study only.
With time domain reflectometry (TDR) two dispersive parameters, the dielectric constant, e, and the electrical conductivity, a can be measured. Both parameters are nonlinear functions of the volume fractions in soil. Because the volume function of water (0w) can change widely in the same soil, empirical equations have been derived to describe these relations. In this paper, a theoretical model is proposed based upon the theory of dispersive behaviour. This is compared with the empirical equations.
The agreement between the empirical and theoretical aproaches was highly significant: the e(Ow) relation of Topp et aL had a coefficient of determination r 2 = 0.996 and the e(0u) relation of Smith and Tice, for the unfrozen water content, 0u, at temperatures below 0~ had an r 2 = 0.997. To obtain a(0w) relations, calibration measurements were performed on two soils: Caledon sand and Guelph silt loam. For both soils, an r2= 0.983 was obtained between the theoretical model and the measured values. The correct relations are especially important at low water contents, where the interaction between water molecules and soil particles is strong.
π SIMILAR VOLUMES
In a recent paper Payne 1 gives a very interesting and informative review of Time-Domain Reflectometry (TDR) but he fails in his attempt to apply this technique to transient electrochemical kinetic and double-layer analysis. He states that the conventional electronic techniques of Bockris and cowork
## Abstract Timeβdomain reflectometry (TDR) sensors have been widely used in many fields for measurement of soil water content. However, few TDR sensors have been used in a hyperβarid environment (e.g. less than 0Β·05 m^3^ m^β3^), and such sensor applicability is not yet confirmed. In this study we