001     190118
005     20250129092412.0
020 _ _ |a 978-3-95806-035-7
024 7 _ |2 Handle
|a 2128/8572
024 7 _ |2 ISSN
|a 1866-1793
037 _ _ |a FZJ-2015-03058
041 _ _ |a English
100 1 _ |0 P:(DE-Juel1)140421
|a Mester, Achim
|b 0
|e Corresponding Author
|g male
|u fzj
245 _ _ |a Quantitative Two-Layer Inversion and Customizable Sensor-Array Instrument for Electromagnetic Induction based Soil Conductivity Estimation
|f 2015-02-01
260 _ _ |a Jülich
|b Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
|c 2015
300 _ _ |a viii, 119 S.
336 7 _ |0 PUB:(DE-HGF)11
|2 PUB:(DE-HGF)
|a Dissertation / PhD Thesis
|b phd
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|s 1430828793_21698
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|2 PUB:(DE-HGF)
|a Book
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336 7 _ |0 2
|2 EndNote
|a Thesis
336 7 _ |2 DRIVER
|a doctoralThesis
336 7 _ |2 BibTeX
|a PHDTHESIS
336 7 _ |2 DataCite
|a Output Types/Dissertation
336 7 _ |2 ORCID
|a DISSERTATION
490 0 _ |a Schriften des Forschungszentrums Jülich Reihe Energie & Umwelt / Energy & Environment
|v 249
502 _ _ |a RWTH Aachen, Diss., 2014
|b Dr.
|c RWTH Aachen
|d 2014
520 _ _ |a Electromagnetic (EM) measurement methods oer the great potential to non-invasively and contactlessly obtain geological and hydrological soil properties of the uppermost six meters of the subsurface with an areal resolution in the sub-meter range. The presented work is focused on small-sized frequency domain `electromagnetic induction' (EMI) systems which combine the transmitter (Tx) and receiver (Rx) unit in one portable construction and obtain the apparent electrical conductivity ($\sigma_{a}$) of the sensed soil volume by inducing electrical currents and measuring the responding electromagnetic field. The sensing depth of EMI instruments depends on the sensor conguration and in particular the coil orientation and Tx-Rx separation. In principle, multi-conguration EMI data can be inverted for the electrical conductivity distribution over depth. However, there is a demand for efficient inversion algorithms and high-quality EMI data from different sensing depths to perform such an inversion. Here, a novel one-dimensional global-local inversion approach is implemented which evaluates the mist between EMI data and forward modeled data for a two-layer soil using a L1-norm objective function. The global approach is based on a grid search for reasonable model parameters in combination with the local-sensitivity forward model. The two soil models with the smallest misfit are refined using the (local) simplex search algorithm with the more precise full solution electromagnetic forward model. The algorithm is analyzed using synthetic EMI data. Applying the inversion on quantitative EMI transect data from two commercial devices with eight different sensor configurations results in a two-layer electrical conductivity model with lateral and vertical conductivity changes that are in good agreement with a collocated electrical resistivity tomography data set. To improve the depth-resolution beyond available fixed congurations, a novel EMI prototype system (ElMa1) with customizable sensor-array is developed, containing multiple modular sensor units which can be flexibly arranged by the operator for each survey, ensuring optimal depth-sensitivity (i.e. coil orientations and Tx-Rx separations) for the specific investigation. The sensor units consist of coil-based transmitter and receiver circuits which allow for the measurement of the magnetic flux and the sensor impedance in a frequency range between 3 and 33 kHz, respectively. To allow for flexible sensor congurations, data processing and signal optimization, the transmitter current and the receiver voltages are separately digitized using 24-bit analog-to-digital converters (ADC's) which provide a high dynamic range and phase stability. For a measurement time of 0.5 s, the ElMa1 system achieves an instrumental $\sigma_{a}$-accuracy of 1 mS/m at 20 kHz for the intended Tx-Rx separation of 1.0 m and an accuracy of 10 mS/m for a less favorable conguration with smaller Tx-Rx separation of 0.3 m and smaller measurement frequency of 5 kHz, both observed under stable temperature conditions. In addition, experimental data were corrected for temperature-induced system drifts by simulating the electrical circuit of the sensor system using spectral measurements [...]
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773 _ _ |y 2015
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