Study on the low power consumption of racetrack fluxgate

The paper investigates a method to lower power consumption of a racetrack fluxgate sensor. For sine wave excitation, there exists an optimum excitation current (OEC) that makes the fluxgate obtain the highest sensitivity. We analyzed and designed a contracted core structure with different core cross-sectional areas inside the excitation coil and the pick up coil, and then derived an equation to describe the relationship between OEC and the structure size. The OEC decreases with square of the ratio of pick up core cross-section to that of the excitation core, while it changes little with the ratio of their lengths. This enables us to reduce fluxgate power consumption without losing sensitivity. By further analysis to the ratios of the core cross-section, we have obtained an equation regarding the minimum excitation current for contracted core structure fluxgate when the ratio tends to zero. The minimum excitation current is proportional to the core length of the pick up coil and inversely proportional to the number of turns in the excitation coil. Eight fluxgate sensors with different ratio of core cross-sections and core lengths were developed and investigated. The experiment results conform the validity of the equations mentioned. When the core cross-section ratio changes from 1 to 0.2, the power consumption from the experiments reduces from 41 mW to 1.2 mW with no sensitivity loss.