scholarly journals A Seven-Rod Dielectric Sensor for Determination of Soil Moisture in Well-Defined Sample Volumes

Sensors ◽  
2019 ◽  
Vol 19 (7) ◽  
pp. 1646 ◽  
Author(s):  
Justyna Szerement ◽  
Aleksandra Woszczyk ◽  
Agnieszka Szypłowska ◽  
Marcin Kafarski ◽  
Arkadiusz Lewandowski ◽  
...  
Keyword(s):  
Dielectric Permittivity ◽  
Water Content ◽  
Sandy Loam ◽  
Sample Volume ◽  
Time Domain Reflectometry ◽  
Complex Dielectric Permittivity ◽  
The Real ◽  
Electromagnetic Simulations ◽  
Different Diameters ◽  
Permittivity Spectrum

This paper presents a novel seven-rod sensor used for time-domain reflectometry (TDR) and frequency-domain reflectometry (FDR) measurements of soil water content in a well-defined sample volume. The probe directly measures the complex dielectric permittivity spectrum and for this purpose requires three calibration media: air, water, and ethanol. Firstly, electromagnetic simulations were used to study the influence of the diameter of a container on the sensitivity zone of the probe with respect to the measured calibration media and isopropanol as a verification liquid. Next, the probe was tested in three soils—sandy loam and two silt loams—with six water contents from air-dry to saturation. The conversion from S 11 parameters to complex dielectric permittivity from vector network analyzer (VNA) measurements was obtained using an open-ended liquid procedure. The simulation and measurement results for the real part of the isopropanol dielectric permittivity obtained from four containers with different diameters were in good agreement with literature data up to 200 MHz. The real part of the dielectric permittivity was extracted and related to the moisture of the tested soil samples. Relations between the volumetric water content and the real part of the dielectric permittivity (by FDR) and apparent dielectric permittivity (by TDR) were compared with Topp’s equation. It was concluded that the best fit to Topp’s equation was observed in the case of a sandy loam. Data calculated according to the equation proposed by Malicki, Plagge, and Roth gave results closer to Topp’s calibration. The obtained results indicated that the seven-rod probe can be used to accurately measure of the dielectric permittivity spectrum in a well-defined sample volume of about 8 cm3 in the frequency range from 20 MHz to 200 MHz.

scholarly journals Seven-Rod Dielectric Sensor for Determination of Soil Moisture in Small Volumes

Proceedings ◽  
2020 ◽  
Vol 15 (1) ◽  
pp. 49
Author(s):  
Justyna Szerement ◽  
Aleksandra Woszczyk ◽  
Agnieszka Szypłowska ◽  
Marcin Kafarski ◽  
Arkadiusz Lewandowski ◽  
...  
Keyword(s):  
Dielectric Permittivity ◽  
Sandy Loam ◽  
Sample Volume ◽  
Small Sample ◽  
Silt Loam ◽  
Frequency Range ◽  
Fem Simulations ◽  
Dielectric Sensor ◽  
Permittivity Spectrum

The paper presents the performance of a seven-rod dielectric probe for determination of soil dielectric permittivity using FEM simulations as well as FDR and TDR measurements. The volume of the sensitivity zone of the tested probe was assessed basing on the simulations and measurement in liquids. The probe was also tested in two soils, sandy loam and silt loam. The obtained results suggested that the seven-rod probe can be used to accurately measure the dielectric permittivity spectrum in a small sample volume of about 8 cm3 in a frequency range from 20 MHz to 200 MHz.

scholarly journals Development of a Resonant Microwave Sensor for Sediment Density Characterization

Sensors ◽  
2020 ◽  
Vol 20 (4) ◽  
pp. 1058 ◽  
Author(s):  
R. Mansour ◽  
S. Rioual ◽  
B. Lescop ◽  
P. Talbot ◽  
M. Abboud ◽  
...  
Keyword(s):  
Dielectric Permittivity ◽  
Water Content ◽  
Printed Circuit Board ◽  
Ionic Species ◽  
Bulk Water ◽  
Circuit Board ◽  
Complex Dielectric Permittivity ◽  
Polarization Sensitivity ◽  
Electrode Polarization ◽  
The Real

In this study, a sensor based on the development of a planar antenna immersed in sediments dedicated to water content monitoring in this type of material is proposed and experimentally validated. It is produced by a conventional Printed Circuit Board (PCB) manufacturing process on a double-sided metalized FR4 substrate. The sensitivity of the sensor is ensured by the variation of the real part of the complex dielectric permittivity of sediments with water content at around 1 GHz. As shown, in this frequency range, electrode polarization and Maxwell–Wagner polarization effects become negligible, leading to only a bulk water polarization sensitivity. The sensor operates in the reflection mode by monitoring the variation of the resonant frequency as a function of the sediment density through the S11 reflection measurements. An experimental sensitivity of 820   MHz . g − 1 . cm 3 was achieved. Despite the simplification of data interpretation at the considered frequency, the influence of ionic species such as NaCl in sediments on the real part of the relative complex dielectric permittivity is highlighted. This demonstrates the importance of considering a second parameter such as the S11 level at low frequency or the electrical conductivity to extract the density from the frequency measurements.

A modified dielectric probe for increased measurement volume of soil water content

2020 ◽  
Author(s):  
Aleksandra Woszczyk ◽  
Justyna Szerement ◽  
Arkadiusz Lewandowski ◽  
Marcin Kafarski ◽  
Agnieszka Szypłowska ◽  
...  
Keyword(s):  
Dielectric Permittivity ◽  
Water Content ◽  
Electromagnetic Waves ◽  
Mechanical Damage ◽  
Direct Methods ◽  
Soil Disturbance ◽  
Sample Volume ◽  
Time Domain Reflectometry ◽  
Frequency Range ◽  
Probe Calibration

<p>The information of water amount in soil is essential in many fields (e.g. agriculture, forestry, hydrology). Methods to determine water content (WC) can be classified as direct and indirect. Direct methods are connected with the destruction of a sample, are time-consuming and impractical for the measurements in the crop fields. Indirect methods ensure non-destructive and in situ measurements and depend on monitoring a dielectric soil property which is a function of WC. The soil dielectric permittivity is one of the used properties which may be determined by time domain reflectometry (TDR) or frequency domain reflectometry (FDR) techniques. TDR probes are expensive and can be easily damaged at multiple insertions to soil. The open-ended (OE) probes, well-known for their application in the measurements of the complex dielectric permittivity of materials in broadband frequency range, are more resistant to mechanical damage but they are characterized by low penetration depth of electromagnetic waves. Therefore, there is a need to develop sensors able to measure bigger volumes and at the same time sufficiently durable for multiple insertions in soil.     </p><p>The objective of this work was to test the performance of an open-ended dielectric probe with an antenna (OE-A) in the frequency range 1 MHz – 6 GHz for two mineral soils using vector network analyzer (VNA) one port (reflective) measurements. Firstly, numerical simulations of the probe using Ansys HFSS software were performed. Secondly, the probe calibration was done on the reference materials (air, distilled water and ethanol). Thirdly, the soils measurements were done to check the possibility to determine soil moisture.   </p><p>The obtained results show that the tested probe can be applied for fast moisture measurement with minimal soil disturbance. The real part of dielectric permittivity (ε’) obtained for the tested soils was connected with their moisture and the relation between ε’ and volumetric water content was determined. Additionally, the effect of the sample volume was considered and the relation between the high-frequency limit and diameter of the sample was determined.     </p><p>Acknowledgement:</p><p>This research was supported by the National Centre for Research and Development (BIOSTRATEG/343547/8/NCBR/2017).</p>

Dielectric Spectra of BaTiO3-Based Ceramics Measured by Impedance Analyzer Using Micro Planar Electrodes

2006 ◽  
Vol 301 ◽  
pp. 129-134 ◽  
Author(s):  
Jianyong Li ◽  
Hirofumi Kakemoto ◽  
Satoshi Wada ◽  
Takaaki Tsurumi
Keyword(s):  
Dielectric Permittivity ◽  
Measuring Method ◽  
Complex Dielectric Permittivity ◽  
Relative Dielectric Permittivity ◽  
High Permittivity ◽  
Impedance Analyzer ◽  
Electromagnetic Simulations ◽  
Planar Electrodes ◽  
Complex Admittance ◽  
Frequency Curves

A new measuring method and analyzing procedure were proposed to determine the complex dielectric permittivity of materials with relatively high permittivity using an RF-impedance analyzer. Samples used for the measurement were (Ba0.6Sr0.4)TiO3 and Ba(Zr0.25Ti0.75)O3 ceramics. Micro planar electrodes were used for the measurement of complex admittance of these samples. Electromagnetic simulations were carried out for determining the relative dielectric permittivity and dielectric loss. The complex dielectric permittivity vs. frequency curves of Ba(Zr0.25Ti0.75)O3 showed a broad dielectric relaxation, while that of (Ba0.6Sr0.4)TiO3 was almost flat up to 3 GHz.

Verification of soil salinity index model based on 0.02–3 GHz complex dielectric permittivity spectrum measurements

2019 ◽  
Vol 574 ◽  
pp. 517-528 ◽  
Author(s):  
Agnieszka Szypłowska ◽  
Justyna Szerement ◽  
Arkadiusz Lewandowski ◽  
Marcin Kafarski ◽  
Andrzej Wilczek ◽  
...  
Keyword(s):  
Dielectric Permittivity ◽  
Soil Salinity ◽  
Complex Dielectric Permittivity ◽  
Index Model ◽  
Model Based ◽  
Spectrum Measurements ◽  
Salinity Index ◽  
Permittivity Spectrum

Enhancing modelled water content by dielectric permittivity in stony soils

Soil Research ◽  
2016 ◽  
Vol 54 (3) ◽  
pp. 360 ◽  
Author(s):  
M. Pakparvar ◽  
W. Cornelis ◽  
D. Gabriels ◽  
Z. Mansouri ◽  
S. A. Kowsar
Keyword(s):  
Dielectric Permittivity ◽  
Water Content ◽  
Mixture Model ◽  
Model Performance ◽  
Time Domain Reflectometry ◽  
Soil Conditions ◽  
Probe Type ◽  
Regression Equations ◽  
Deep Well ◽  
Reflection Time

Applicability of time domain reflectometry (TDR) under naturally distributed stone fragments in soils has seldom been investigated. A multilayer profile of a 30-m-deep well was sampled and the natural distribution of stone fragments in the soils was replicated in the laboratory. Gravimetric soil water content (SWC) was measured simultaneously with TDR dielectric permittivity (Ka) readings and bulk densities in three subsamples as replications. Two connector and buriable probes and three reflection-time capture windows (10, 20 and 40 ns) were used for the measurements. These were repeated for sieved soil samples <2 mm with fixed, pre-measured bulk densities. Measurements of Ka and observed SWC were repeated for extension-cable lengths of 3–30 m. All measurements were taken in samples saturated from the bottom. A semi-empirical mixture model was applied for different fractions of stony samples in order to convert bulk Ka to bulk volumetric SWC (θv) by the mixture model (θvmx), to be compared with θv by the conventional Topp equation (θvTp). An improvement in model performance was observed with lower root-mean-square error (RMSE, 0.02–0.04 v. 0.07–0.1) and ratio of RMSE to observation standard deviation (0.32–0.87 v. 1.07–3.05) for θvmx compared with θvTp. This approach for converting the in-situ measured dielectric permittivity to the θv of the bulk soil can be applied based on the determined stoniness. The 15-cm, 2-rod (connector) probe type with capture windows 20 ns resulted in a better performance than the 20-cm, 3-rod (buriable) probe type with capture windows 10 and 40 ns. Development of regression equations for the stone-free samples resulted in calibrated equations for converting the measured Ka to θv with better results (RMSE ~0.002 m3 m–3) than those obtained using the Topp equation. In contrast to the traditional equation, new sets of coefficients for the Topp equation were also capable of estimating extremely low θv values of ≤0.02 m3 m–3 where the minimum calculated θv values were adequately similar to the observed ones. Noticeable effects of cable length on measured Ka were found for lengths exceeding 10 m. Accurate Ka values might be obtained in similar soil conditions if the suggested regression equations are employed, provided a correction is made for the extension cables.

Wideband Characterization of Soil Complex Dielectric Permittivity Spectrum

2020 ◽  
Author(s):  
Agnieszka Szyplowska ◽  
Hironobu Saito ◽  
Shin Yagihara ◽  
Minoru Fukuzaki ◽  
Kahori Furuhata ◽  
...  
Keyword(s):  
Dielectric Permittivity ◽  
Complex Dielectric Permittivity ◽  
Soil Complex ◽  
Permittivity Spectrum
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