Reduction of magnetic noise limits of orthogonal fluxgate sensor

Research on magnetic sensors has been carried out in recent years to enhance sensing capability, enabling us to understand the Earth's magnetic field changes [1] with better sensitivities of 10 À10 to 10 À2 T. [2] Magnetic field sensors have been extensively investigated according to their operating principles and actions in various applications. Sensitivity and selectivity are the two essential properties crucial in the evolution of magnetic field sensors to achieve high fidelity outputs. The former is strengthened by increasing the sensor area and improvements to the planar surface with various Nano-materials. In contrast, the latter is improved by using multiple materials and techniques to enhance interfacial interactions.Magnetic sensors detect disturbances and changes in magnetic fields such as force, direction, and flux. It is a transducer that converts a magnetic field into an electrical voltage. There are several types of magnetic field sensors, each with its own sensitivity range. In addition to sensitivity, the temperature range, the physical size of the sensor, and its on-chip manufacturability must all be considered. Magnetic fields of less than 100 pT are extremely weak and far below the earth's magnetic field. Earth magnetic field sensors have a sensitivity range of 10 μT to a few micro-Tesla, while bias magnet field (high field) sensors have a sensitivity of more than 1 mT.Magnetic fields of less than 100 pT are extremely weak and far below the earth's magnetic field. Earth magnetic field sensors have a sensitivity range of 10 μT to a few micro-Tesla, while bias magnet field (high field) sensors have a sensitivity of more than 1 mT. The most sensitive low-field sensor is the superconducting quantum interference device (SQUID). It is based on Brian J. Josephson's research on a point-contact connection for measuring extremely low currents.The SQUID ring, the radio-frequency coil, and the big antenna loop are all superconducting components of the SQUID sensor. All three must be cooled to the point where they become superconducting. The SQUID itself is small, but the requirement for liquid helium cooling makes the entire apparatus big and hefty. Magnetoresistive sensors (MR) have a high sensitivity, are inexpensive to manufacture, and are small in size. However, they have poor noise performance and linearity, as well as a small dynamic range, making them unappealing and unsuitable for many low-noise applications. Furthermore, as the power usage is reduced, their sensitivity degrades.Search-coil or induction sensors are high-sensitivity, lowpower sensors, but their sensitivity decreases as the cross-section area decreases, making miniaturization ineffective. Because search coils can detect an alternating current magnetic field, they cannot detect a static magnetic field like the Earth's magnetic field. Magnetic sensors based on semiconductors, such as Hall-Effect sensors, magnetotransistors, and magnetodiodes, are very small in size. Because of its low manufacturing cost

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Section: Parallel Fluxgate Sensorsmentioning

confidence: 99%

Fabrication Advancements in Integrated Fluxgate Sensors: A Mini Review

2022

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“…This brings excellent magnetic properties, such as low coercivity (tens of A/m [ 2 , 3 ]) and vanishing magnetostriction (

) [ 4 , 5 ]. These characteristics make Cobalt-rich wires ideal for different magnetic sensors [ 6 , 7 , 8 , 9 , 10 , 11 , 12 ]. Among them, orthogonal fluxgates in fundamental mode [ 13 ] have shown a remarkable low noise due to the mechanism that keeps their magnetization always in a saturated state, reducing the Barkhause noise.…”

Section: Introductionmentioning

confidence: 99%

An Improved Composition of CoFeSiB Alloy for Orthogonal Fluxgates

Butta

Janošek

Pařez

et al. 2022

Sensors

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Orthogonal fluxgates in fundamental mode based on (Co0.94Fe0.06)72.5Si12.5B15 cores have recorded very low noise in literature, especially if Joule annealing is performed on the core for a short period of time. However, for annealing time longer than 20–30 min, the noise of the sensor has a tendency to increase. In this work, we investigated this phenomenon, and we have found its origin in a monotonic increase of magnetostriction during the annealing process. We show that the wires with vanishing magnetostriction in their as-cast form exhibit positive magnetostriction after long-time annealing (more than 30 min), which increases the noise of the sensor. After researching the effect of the magnetostriction after annealing on the noise, we propose an alloy with a reduced amount of iron. Less iron leads to a larger as-cast negative magnetostriction, which becomes almost zero after long-time annealing (60 min), bringing further reduction of noise. We prove this effect on two wires from two different manufacturers, although with the same composition. The noise decrease with prolonged annealing is mainly observable in the low-frequency region: at 100 mHz, the noise of a single-wire sensor decreased from 20pT/Hz to 6pT/Hz when the annealing time was prolonged from 10 to 60 min.

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