A numerical analysis of the effects of coatings and gaps upon relative dielectric permittivity measurement with time domain reflectometry

1997 ◽  
Vol 33 (6) ◽  
pp. 1455-1460 ◽  
Author(s):  
J. H. Knight ◽  
P. A. Ferré ◽  
D. L. Rudolph ◽  
R. G. Kachanoski
Keyword(s):  
Numerical Analysis ◽  
Dielectric Permittivity ◽  
Time Domain ◽  
Time Domain Reflectometry ◽  
Relative Dielectric Permittivity ◽  
Permittivity Measurement

Time-domain reflectometry — parametric study for the evaluation of physical properties in soils

2009 ◽  
Vol 46 (7) ◽  
pp. 753-767 ◽  
Author(s):  
Jeffrey M. Schneider ◽  
Dante Fratta
Keyword(s):  
Dielectric Permittivity ◽  
Time Domain ◽  
Parametric Study ◽  
Capillary Rise ◽  
Time Domain Reflectometry ◽  
Relative Dielectric Permittivity ◽  
Proper Understanding ◽  
Abrupt Changes ◽  
Sand And Gravel

Time-domain reflectometry (TDR) has become a commonly used method in geotechnical engineering to measure the volumetric water content and electrical conductivity in soils. The ability of TDR to accurately determine soil properties depends on the proper understanding of the parameters that affect the propagation of an electromagnetic pulse along the TDR waveguide. The purpose of this paper is to document a parametric study and analyses aimed at gaining a better understanding of TDR measurements and to evaluate the limits in the measurement technique. A parametric study on TDR signals was performed by determining the effects of heterogeneities in the dielectric permittivity, conductivity, and magnetic permeability in sand and gravel specimens. Impedance differences in the probe head were found to contribute to inaccurate travel-time measurements that affect material dielectric permittivity calculations. The calculated relative dielectric permittivity may also be dependent on local changes in porosity near the probes. Tests performed in layered materials indicate that TDR can be used to find abrupt changes in material permittivity, such as the depth to saturation. However, problems in the determination of capillary rise may contribute to uncertainties in the proper determination of permittivity and thicknesses of layers. The presence of ferromagnetic materials was found to change the measured electromagnetic wave velocity. However, the properties of materials outside the radius defined by the probes and beneath the probes minimally affected the TDR results in the two-rod probe used.

scholarly journals Estimating Pore Water Electrical Conductivity of Sandy Soil from Time Domain Reflectometry Records Using a Time-Varying Dynamic Linear Model

Sensors ◽  
2018 ◽  
Vol 18 (12) ◽  
pp. 4403 ◽  
Author(s):  
Basem Aljoumani ◽  
Jose Sanchez-Espigares ◽  
Gerd Wessolek
Keyword(s):  
Electrical Conductivity ◽  
Dielectric Permittivity ◽  
Linear Relationship ◽  
Linear Model ◽  
Pore Water ◽  
Sandy Soil ◽  
Time Domain ◽  
Time Domain Reflectometry ◽  
Relative Dielectric Permittivity ◽  
Time Varying

Despite the importance of computing soil pore water electrical conductivity (σp) from soil bulk electrical conductivity (σb) in ecological and hydrological applications, a good method of doing so remains elusive. The Hilhorst concept offers a theoretical model describing a linear relationship between σb, and relative dielectric permittivity (εb) in moist soil. The reciprocal of pore water electrical conductivity (1/σp) appears as a slope of the Hilhorst model and the ordinary least squares (OLS) of this linear relationship yields a single estimate ( 1 / σ p ^ ) of the regression parameter vector (σp) for the entire data. This study was carried out on a sandy soil under laboratory conditions. We used a time-varying dynamic linear model (DLM) and the Kalman filter (Kf) to estimate the evolution of σp over time. A time series of the relative dielectric permittivity (εb) and σb of the soil were measured using time domain reflectometry (TDR) at different depths in a soil column to transform the deterministic Hilhorst model into a stochastic model and evaluate the linear relationship between εb and σb in order to capture deterministic changes to (1/σp). Applying the Hilhorst model, strong positive autocorrelations between the residuals could be found. By using and modifying them to DLM, the observed and modeled data of εb obtain a much better match and the estimated evolution of σp converged to its true value. Moreover, the offset of this linear relation varies for each soil depth.

Considerations for Improving the Accuracy of Permittivity Measurement using Time Domain Reflectometry

2003 ◽  
Vol 67 (1) ◽  
pp. 62 ◽  
Author(s):  
D. A. Robinson ◽  
M. Schaap ◽  
S. B. Jones ◽  
S. P. Friedman ◽  
C. M. K. Gardner
Keyword(s):  
Time Domain ◽  
Time Domain Reflectometry ◽  
Permittivity Measurement

scholarly journals Time Domain Reflectometry (TDR) technique – A solution to monitor moisture content in construction materials

2020 ◽  
Vol 172 ◽  
pp. 17001
Author(s):  
Teresa Stingl Freitas ◽  
Ana Sofia Guimarães ◽  
Staf Roels ◽  
Vasco Peixoto de Freitas ◽  
Andrea Cataldo
Keyword(s):  
Moisture Content ◽  
Time Domain ◽  
Building Materials ◽  
Correct Diagnosis ◽  
Construction Materials ◽  
Gravimetric Method ◽  
Reference Method ◽  
Time Domain Reflectometry ◽  
Relative Dielectric Permittivity ◽  
Porous Building Materials

Measuring moisture content in building materials is crucial for the correct diagnosis of buildings’ pathologies and for the efficiency evaluation of the treatment solution applied. There are several different techniques available to measure the moisture content in construction materials. However, perform long-term minor-destructive measurements is still a great challenge. The TDR – Time Domain Reflectometry – technique is commonly used for moisture content measurements in soils, but is considered a relatively new method with regard to its application in construction materials. In the present state of research, the current use of the TDR technique for monitoring moisture content in all types of consolidated porous building materials is not possible yet. Indeed, the empirical conversion functions proposed for soils are mostly not suitable for building materials. Furthermore, to successfully use the TDR technique, a good contact between the TDR probe and the material under study is required, which may be difficult to achieve in hard materials. In this paper, the TDR technique was implemented in two limestone walls constructed in the lab to test experimentally the efficiency of a wall-base ventilation channel to speed up drying after a flood. Each wall was equipped with four two-rod TDR probes for continuous monitoring the moisture content in both situations: with and without the ventilation channel. All the equipment used, procedures followed during the drilling until the probes’ final installation, as well as the individual calibration required for each probe are explained in detail. Instead of using unsuitable functions proposed for soils, the evaluation of the moisture content from the apparent relative dielectric permittivity measured was established using as reference method the gravimetric method. The results obtained suggest that the TDR technique is suitable for moisture content monitoring in consolidated porous building materials.

scholarly journals Dielectric dispersion and thermodynamic behavior of stearic acid binary mixtures with alcohol as co-solvent using time domain reflectometry

2017 ◽  
Vol 07 (04) ◽  
pp. 1750027 ◽  
Author(s):  
M. Maria Sylvester ◽  
T. Ganesh ◽  
D. J. S. Anand Karunakaran ◽  
P. Senthilkumar ◽  
Praveen G. Hudge ◽  
...  
Keyword(s):  
Dielectric Permittivity ◽  
Stearic Acid ◽  
Time Domain ◽  
Dielectric Strength ◽  
Calibration Method ◽  
Time Domain Reflectometry ◽  
Ternary Mixtures ◽  
Relaxation Dynamics ◽  
Dielectric Parameters ◽  
Strength Formula

Dielectric permittivity and relaxation dynamics of binary and ternary mixture of stearic acid on various concentration and their thermodynamic effects are studied. The static dielectric constant ([Formula: see text]), dielectric permittivity ([Formula: see text]) and dielectric loss ([Formula: see text]) are found by bilinear calibration. The relaxation time ([Formula: see text]), dielectric strength ([Formula: see text]) and the excess permittivity ([Formula: see text]) are found. The thermodynamic parameters such as enthalpy ([Formula: see text]), entropy ([Formula: see text]) and Gibb’s free energy ([Formula: see text]) are evolved. The significant changes in dielectric parameters are due to the intramolecular and intermolecular interactions in response to the applied frequency. The permittivity spectra of stearic acid–alcohol in the frequency range of 10[Formula: see text]MHz to 30[Formula: see text]GHz have been measured using picoseconds Time Domain Reflectometry (TDR). The dielectric parameters ([Formula: see text], [Formula: see text], [Formula: see text]) are found by bilinear calibration method. Influence of temperature in intermolecular interaction and the relaxation process are also studied. The FT-IR spectral analysis reveals that the conformation of functional groups and formation for hydrogen bonding are present in both binary and ternary mixtures of stearic acid.

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