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A platform for research: civil engineering, architecture and urbanism
Time Domain Reflectometry
Abstract Originally, the TDR measurement technique was developed to detect defects in telecommunication cables and electrical wires, Moffitt (1964). Within recent decades, TDR was also applied to determine and monitor volumetric moisture contents in particulate and porous media, in particular soil but lately also building materials such as building bricks, concrete, sandstone, etc., see e.g. Dobson et al. (1985), Topp et al. (1980), and Phillipson et al. (2008). TDR is in general based on the measurement of the propagation time of an electromagnetic signal along a wave guide also referred to as probe, usually there and back. In the low frequency range, i.e. <10 GHz, water possesses a considerably higher relative permittivity (ε w ≈ 80) than mineral compounds (ε s ≈ 4) or air (ε a ≈ 1). From the measurement of the propagation time of an electromagnetic signal along a wave-guide, the mean relative permittivity, which is among others moisture dependent, of the investigated dielectric material is derived from the reflection picture. Subsequently, the volumetric water content can be determined directly from the mean relative permittivity applying suitable material functions, which relate mean relative permittivity and volumetric moisture content.
Time Domain Reflectometry
Abstract Originally, the TDR measurement technique was developed to detect defects in telecommunication cables and electrical wires, Moffitt (1964). Within recent decades, TDR was also applied to determine and monitor volumetric moisture contents in particulate and porous media, in particular soil but lately also building materials such as building bricks, concrete, sandstone, etc., see e.g. Dobson et al. (1985), Topp et al. (1980), and Phillipson et al. (2008). TDR is in general based on the measurement of the propagation time of an electromagnetic signal along a wave guide also referred to as probe, usually there and back. In the low frequency range, i.e. <10 GHz, water possesses a considerably higher relative permittivity (ε w ≈ 80) than mineral compounds (ε s ≈ 4) or air (ε a ≈ 1). From the measurement of the propagation time of an electromagnetic signal along a wave-guide, the mean relative permittivity, which is among others moisture dependent, of the investigated dielectric material is derived from the reflection picture. Subsequently, the volumetric water content can be determined directly from the mean relative permittivity applying suitable material functions, which relate mean relative permittivity and volumetric moisture content.
Time Domain Reflectometry
Michel, Alexander (author) / Sobczuk, Henryk (author) / Kielsgaard Hansen, Kurt (author)
2018-01-01
8 pages
Article/Chapter (Book)
Electronic Resource
English
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