Two-axis Fluxgate Research Articles

Multilayered vectorial fluxgate magnetometer based on PCB technology and dispensing process

In this study, a two-axis fluxgate sensor based on PCB technology is presented. The sensor consists of multiple layers and uses silver ink to form vias. Each layer of the coil is designed in a rectangular spiral shape and a cross-shaped magnetic core is utilized to achieve two-axis sensing. The fabricated sensor consists of one excitation coil layer, three sensing coil layers and a magnetic core with dimensions of 50 mm × 50 mm. With a sinusoidal excitation signal at a frequency of 50 kHz and a current of 500 mA, the proposed sensor has a sensitivity of 2496 V T−1 at 80 µT. It can also sense vector magnetic fields in a plane by comparing the two-axis signals.

A Nonlinear Calibration Algorithm Based on Harmonic Decomposition for Two-Axis Fluxgate Sensors.

Nonlinearity is a prominent limitation to the calibration performance for two-axis fluxgate sensors. In this paper, a novel nonlinear calibration algorithm taking into account the nonlinearity of errors is proposed. In order to establish the nonlinear calibration model, the combined effort of all time-invariant errors is analyzed in detail, and then harmonic decomposition method is utilized to estimate the compensation coefficients. Meanwhile, the proposed nonlinear calibration algorithm is validated and compared with a classical calibration algorithm by experiments. The experimental results show that, after the nonlinear calibration, the maximum deviation of magnetic field magnitude is decreased from 1302 nT to 30 nT, which is smaller than 81 nT after the classical calibration. Furthermore, for the two-axis fluxgate sensor used as magnetic compass, the maximum error of heading is corrected from 1.86° to 0.07°, which is approximately 11% in contrast with 0.62° after the classical calibration. The results suggest an effective way to improve the calibration performance of two-axis fluxgate sensors.

Two-axis micro fluxgate sensor on single chip

We present a two-axis micro fluxgate sensor on single chip for electronic compassing function. To measure X- and Y-axis magnetic fields, functional two fluxgate sensors were perpendicularly aligned and connected each other. The fluxgate sensor was composed of square-ring shaped magnetic core and solenoid excitation and pick-up coils. The solenoid coils and magnetic core were separated by benzocyclobutane which had high insulation and good planarization characters. Copper coil patterns of 10 μm width and 6 μm thickness were electroplated on Ti (300 A)/Cu (1,500 A) seed layers. 3 μm thick Ni0.8Fe0.2 (permalloy) film for the magnetic core was also electroplated under 2,000 gauss. Excellent linear response over the range of −100 μT to +100 μT was obtained with the sensitivity of ∼280 V/T. Actual chip size was 3.1×3.1 mm2. The sine and cosine signals of two-axis fluxgate sensor had a good function of azimuth compass.

Low-power 2-D fully integrated CMOS fluxgate magnetometer

In this paper, we present a low-power, two-axis fluxgate magnetometer. The planar sensor is integrated in a standard CMOS process, which provides metal layers for the coils and electronics for the signal extraction and processing. The ferromagnetic core is placed diagonally above the four excitation coils by a compatible photolithographic post process, performed on a whole wafer. The sensor works using the single-core principle, with a modulation technique to lower the noise and the offset at the output. In contrast to traditional fluxgate approaches, the sensor features a high degree of integration and minimal power consumption at 2.5 V of supply voltage that makes it suitable for portable applications. A novel digital feedback principle is integrated to linearize the sensor characteristics and to extend the linear working range.

Biaxial magnetometer sensor

A simple two-axis fluxgate magnetometer has been developed to measure weak magnetic fields by using magnetization rotation processes. To obtain these magnetization processes, we use circular discs of a very thin soft magnetic material as cores. These cores are magnetized by a rotating magnetic field high enough to saturate them. Thus, the magnetization processes are due to magnetization rotation and the only losses are due to macro-eddy currents. This kind of device can also be used to measure the magnetic field in two perpendicular directions by using a single core and, in principle, the exciting field frequency can be greater than in conventional fluxgate magnetometers. The maximum calculated sensitivity of this device is 5.3 times higher than that of a conventional fluxgate magnetometer of similar dimensions.

A Marine Electrical Analog-type Dead Reckoning Computer

The device described, which is in prototype form, accepts ship's speed from the Harrier electronic log and heading data from the Halcyon transmitting compass and continuously displays the north–south and east–west components of the water distance traversed from a starting position. It is a development of the Hadrian distance-offtrack computer which, with the Harrier log, has been described in a previous article published in this Journal.The Sensors. Harrier is a through-hull impeller-type electronic log which records distance run in steps of 0·01 n.m. on an electromagnetic counter and indicates speed on a suitably calibrated milliammeter. Halcyon is a recent development, being a two-axis fluxgate transmitting compass which senses the Earth's magnetic field directly, thus avoiding the major problems associated with the use of pivoted magnetic systems in fast power vessels. The two rectilinear fluxgates are mutually perpendicular and are pendulously mounted with their axes in the horizontal plane. Viscous damping prevents their oscillating when subjected to vibration and shock. The outputs of the compass circuits are two d.c. analog signals which represent in magnitude and sign, the sine and cosine of the heading angle respectively.