DESIGN AND DEVELOPMENT OF AN OPTIMIZED FLUXGATE MAGNETOMETER FOR IMPROVED EARTH’S MAGNETIC FIELD STUDIES

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Department of Engineering

ABSTRACT
This research work was centered on optimizing the Fluxgate Magnetometer Sensor (FMS)at reduced noise level and enhanced sensitivity. The FMS was developed using Manganese Zinc (MnZn) ferrite alloy different from the usual permalloy and amorphous alloy materials. The developed FMS using MnZn ferrite achieved reduced sensor dimensions with high sensitivity and reduced noise level, thus meeting the necessary requirements for the earth?s magnetic field studies. However, the sensor was realized using MnZn ferrite ring core material, excitation and pick-up coils, and the interface electronic circuits.The performance of this designed and developed FMS was optimized using the modified Firefly Optimization Algorithm (FOA). The characteristics of the developed fluxgate sensors were modeled using the modified FOA and the matching between the excitation and detection circuits was then considered. Analysis was then carried out to determine the values of relevant parameters using modified FOA written in MATLAB program. The model yielded an accurate prediction of the sensitivity and noise level compared to the commonly used conventional Part-by-Part Optimization (PPO) and analytical optimization techniques.Three ring core FMS with different diameters (14 mm and 10 mm) were constructed based on the PPO technique while 12 mm ring core was constructed based on the FOA technique. Experiments were employed to validate the PPO and the FOA techniques. The sensitivity and noise of the 12 mm ring core external diameter FOA sensor were 64.04mV/μT and 4.94pT/√Hz at 1 Hz in the range of ±75μT, while the sensitivity and noise level of PPO sensor A with 14 mm ring core external diameter and PPO sensor B with 10 mm ring core external diameter were 34.31 mV/μT and 19.50 mV/μT with 12.34 pT/√Hz at 1 Hz and 72.22 pT/√Hz at 1 Hz, respectively in the range of ±75μT. The modified FOA-based sensor, therefore achieved the overall objectives of this research.