Magnetic Sensors Based on Amorphous Ferromagnetic Materials: A Review <s> (b) PCB Technology <s> A new compact 2D planar fluxgate sensor using a ferromagnetic amorphous metal core is described. The fluxgate sensor consists of two orthogonal planar metallic coils and a ring shaped amorphous magnetic ribbon mounted on a PCB substrate. Each planar coil is used alternatively as excitation or as pick-up coil. An electronic interface drives alternatively the two coils and performs a feedback on each sensing coil in order to compensate for the two measured magnetic field omponents. The sensing element has a magnetic sensitivity of 55 VrmT at an excitation frequency of 8.4 kHz with a 160 mApeak driving current. Used as an electronic compass, the reached precision angle is better than 1degree. <s> BIB001 </s> Magnetic Sensors Based on Amorphous Ferromagnetic Materials: A Review <s> (b) PCB Technology <s> Abstract This article describes the design and testing of a planar current fluxgate sensor prototype. The prototype is composed of a fluxgate current sensor totally embedded in printed circuit board combined with signal processing electronics. The fluxgate sensor excitation and pickup coils are implemented as racetrack shaped copper windings in the printed circuit board internal layers and they are surrounded by an electroplated magnetic core consisting of a thin film of nickel–iron alloy. The electronics provides excitation (including saturable inductor) of the fluxgate and signal processing (filtering and synchronous detection) of the pick-up signal. The prototype has been tested over a 2 A current range with sensitivity 28 V/A at 60 kHz. Excitation using a saturable inductor at 60 kHz has been used and 2 A peak–peak value of the excitation current was reached. We decreased consumption in the sensor from 2.6 W for sine-wave excitation to 0.7 W for excitation for saturable inductor. <s> BIB002 </s> Magnetic Sensors Based on Amorphous Ferromagnetic Materials: A Review <s> (b) PCB Technology <s> Abstract A miniature fluxgate sensor with amorphous race-track core manufactured with printed circuit board (PCB) technology is presented in this paper. The number of PCB layers was increased to five; this allowed for increasing the number of turns of pickup/compensating winding (68), resulting in the compensation current in the feedback loop below 15 mA for a 50 μT measured field. The sensor was characterized using pulse excitation (10 kHz, 10% duty); the maximum sensitivity was found to be 615 V/T for 650 mA p–p excitation current with nonlinearity below 0.5% of full scale. In order to improve the long-term and temperature stability of the sensor, a closed-loop regulation of the excitation current amplitude was designed. A three-axial portable magnetometer using gated integrators and pulse excitation was constructed with these sensors. Feedback-loop operation allowed suppressing the nonlinearity below 100 ppm of ±50 μT full-scale, and the sensitivity increased to 120,000 V/T. Long-term stability was found to be 1 nT in 9-h period, and the temperature coefficient of sensitivity decreased to 50 ppm, which was a direct result of controlling the excitation current. <s> BIB003
Printed Circuit Board (PCB) technology also has been widely used in the development of planar fluxgates BIB003 BIB002 . Kejí k et al. BIB001 have recently developed a 2D planar fluxgate composed of two orthogonal plan coils and an amorphous ferromagnetic core in the shape of a PCB ring. Each of the coils has a density of 50 spires/cm and the core consists of a Vitrovac 6025 tape realised by means of photolithography. The detection principle is based on alternating measurements in two directions. In each case, the exciting coil is orthogonal to the measuring axis. As a result, the output voltage of the secondary coil only contains the external field signal. The authors report that the sensor is linear in a range of ±60 μT, showing a sensitivity of 55 V/mT. The application of the sensor is determined by its capacity to measure the components of the Earth's magnetic field, as it were, like an electronic compass. The accuracy level in the obtained angle for a horizontal field of 30 μT is of 1°.