FLUXGATE MAGNETOMETER CALIBRATION : Biot-Savart Calibration Method

• Main Author: Russell, Andrew
• Other Authors: Lapin ammattikorkeakoulu
• Format: Bachelor Thesis
• Language: English
• Published: Lapin ammattikorkeakoulu 2017
• Subjects: Biot-Savart; calibration; fluxgate; geomagnetism; magnetometer; fi=Tieto- ja viestintätekniikka|sv=Informations- och kommunikationsteknik|en=Information and Communications Technology|; Degree Program in Information Technology; Arctic; Sodankylä
• Online Access: http://www.theseus.fi/handle/10024/126871

The aim of the study was to investigate if the law of Biot-Savart could be applied to a method to calibrate a fluxgate magnetometer at Arctic latitudes. The fluxgate sensor to be calibrated was commercially produced and included integrated signal acquisition and output interface circuitry. A mu-metal alloy magnetic field shielding chamber was not available for this study. Standard laboratory test equipment and apparatus were utilized to produce a calibration method with a very modest budget. The law of Biot-Savart was applied to a current loop with square geometry. An equation was derived for the magnitude of the magnetic field at the center of the square current loop. The magnetic field produced was directly proportional to the current flowing through the current loop. The resulting magnetic field was produced in opposition to the ambient geomagnetic field. Taking real-time data from the geophysical observatory at Sodankylä provided an accurate reading for each component of the geomagnetic field. By cancelling the geomagnetic field, the output of the fluxgate sensor was obtained while the magnitude of the surrounding geomagnetic field had been reduced to zero. By varying the current through the square current loop, a range of output values against a range of magnetic field magnitudes were achieved, allowing the linearity of the fluxgate sensor to be observed. Results for the method were achieved only in the z-axis since this is the strongest component of geomagnetic field at arctic latitudes. Results in the x-axis and y-axis were not achieved, being weaker and varied considerably with slight changes in orientation. The absence of a precision mechanism to hold the fluxgate sensor in geographic North-South and East-West alignment made measurements impracticable. The results achieved in the vertical z-axis were consistent and allowed the output of the fluxgate sensor to be plotted against magnetic flux density.