الفهرس 
Study of design considerations of fluxgate sensing element for magnetic field measurement
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Abstract
Recently, magnetic sensors have become vital in several applications. The development of magnetic sensors allows measuring magnetic fields at levels as low as few tens of femtotesla. There are a variety of magnetic sensors that can be used in many sectors, including geophysical survey, space observations, mobile phones, security monitoring, magnetic recording, terrestrial navigation, and biomedical diagnostics. Magnetometers can be categorized, according to their sensitivity, into high; medium and low. Magnetic sensors known as highly sensitive magnetometers can detect magnetic fields as weak as nanotesla.
Due to its usage in different applications, fluxgates sensors are the finest selection if measuring magnetic field in the nanotesla range is required. Fluxgate sensors measure the strength of an external magnetic field in certain direction i.e., they are vector magnetometers. The principle of operation of Fluxgate magnetometers based on manipulating a nonlinear soft magnetic material that is driven to saturation by an alternating excitation current and is modulated by the applied magnetic field to be sensed. The main part of fluxgate sensor is its core, i.e., the sensing element of the sensor. The nonlinear characteristics of core’s magnetic material have a non-negligible influence on sensor’s performance. Therefore, accurate modeling of the nonlinear hysteretic and the dynamic behaviors of the core’s magnetic material is mandatory in order to predict the fluxgate sensor’s behavior under variable operating conditions. For this reason, in this thesis we selected the Jiles-Atherton model, that it is extensively used in hysteresis modeling of magnetic materials, for modeling the fluxgate’s magnetic core. Jiles-Atherton model was selected due to its meaningful physical parameters which make it convenient to represent hysteresis characteristic of the core’s soft magnetic material.
Our work takes place in this context, as in this thesis, we propose comprehensive study to model the behavior of the fluxgate magnetic core, which explains how the current and magnetic distribution inside the core depends on both excitation parameters, and core’s magnetic properties. This study will boost the fluxgate research to further improvement, and will assist the magnetometer’s designers in choosing the appropriate operation conditions. In this thesis the finite element analysis was used to evaluate magnetic flux density, and current density distributions inside the fluxgate’s core, taking into account hysteresis behavior of fluxgate core’s magnetic material. Furthermore, in this thesis, we considered two core’s design configurations, to be investigated, corresponding to different excitation mechanisms.
For each design configuration, detailed finite element study is presented to illustrate influence of frequency, core dimension, and excitation mechanism on current and magnetic distribution inside the sensor’s core. The results presented in the thesis provide a performance map for tracking the operational behavior of the fluxgate core under various magnetic environments. Thus, this thesis fulfills the need to have a prior understanding through virtual prototyping (i.e. simulations) of the fluxgate core in order to guide the researchers to optimize the fluxgate sensor design without investing time and money to build physical prototypes