4 research outputs found
Visualizing the signal of the metal detector and increasing the efficiency of the search
In this thesis, the design and analysis of multi-frequency metal detectors
that allow the classification of metallic objects is explained. The working
method of the designed detector is similar to the continuous wave metal
detector, but it works in the range of 1 kHz to 100 kHz instead of a single
frequency. As the amount of distinctive information from the target object
increases, classification becomes easier.
In the theoretical analysis part of the thesis, the working principles of metal
detectors are explained. In addition, the working methods of pulse induction
metal detectors and continuous wave metal detectors are explained in detail. A
basic induction circuit model has been created to perform electromagnetic
analysis in frequency space. Since it works at low frequencies, the equations
are made easier and their solutions are made by using the quasi-static approach.
In the hardware design part, the appropriate inductance value of the coils in
the 1 kHz - 100 kHz band range is calculated. The induction reset of the
double-D coil, which is suitable for the design, is done. Afterwards, it is
isolated from capacitive effects and external EM noises with metallic fabric.
The weak signals received with the phase inverting differential amplifier are
amplified.
In the data analysis part, a remote computer-controlled test setup was set up
in the laboratory environment. Signal generator and oscilloscope were
controlled via computer with LabVIEW® program. The phase and amplitude
data of the signal received with the LabVIEW® interface are recorded in the
file. With the MATLAB® program, coherent and quadrature signal segments
were created from the phase and amplitude data. The graphs were drawn
according to the phase, amplitude, coherent and quadrature data of the signal
taken from the test objects, and their analyzes were made
A Multidisciplinary Analysis of Frequency Domain Metal Detectors for Humanitarian Demining
This thesis details an analysis of metal detectors (low frequency electromagnetic induction devices) with emphasis on Frequency Domain (FD) systems and the operational conditions of interest to humanitarian demining.
After an initial look at humanitarian demining and a review of their basic principles we turn our attention to electromagnetic induction modelling and to analytical solutions to some basic FD direct (forward) problems. The second half of the thesis focuses then on the analysis of an extensive amount of experimental data. The possibility of target classification is first discussed on a qualitative basis, then quantitatively. Finally, we discuss shape and size determination via near field imaging