| Summary: | 碩士 === 國立臺北科技大學 === 機電整合研究所 === 104 === This research followed the previous research results of CMOS MEMS fluxgate in our laboratory as the basic theoretical knowledge. In this work, a new type of 3-axis micro fluxgate with planar coils, magnetic core and flux guide techniques was designed and manufactured. In this design, the sensor dimension is2.5 mm × 2.5 mm. We used double metal layers for both excitation and sensingcoils. Eight sensing coils were implemented for detection of 3-axis magnetic field with four coils at diagonal positions for sensing the z-axis field component and the other four coils connected in pairs for sensing the x- and y-axis field components. The soft magnetic core, which is made of Metglas cobalt-based magnetic ribbon by wet etching, was aligned and mounted onto the fluxgate chip. Besides, the cylindrical ferrite flux guide with high magnetic permeability rate was placed at the center of the fluxgate chip, which induces the bending flux lines that can be detected by the planar sensing coils. The results showed that with sinewave excitation current of 54 mA at 50 kHz and 2nd harmonics phase sensitive detection, the maximum sensitivity of x-axis is 10 V/T and magnetic field noise is about 1.53 nT/√Hz@1Hz, and sensitivity of y-axis is found to be9.45 V/T with magnetic field noise of 2.34 nT/√Hz@1Hz. Whereas, for z-axis, the sensitivity is 3.95 V/T and magnetic field noise is about 6.66 nT/√Hz@1Hz. For the real application, the designed CMOS 3-axis fluxgate was used successfully as an electronic compass. The obtained results are promising solution to realize a miniature planar 3-axis microfluxgate sensor. Further works to integrate the flux guide, magnetic core, and planar coils into chip scale combining with the CMOS transducer will help realizing a system-on-a-chip (SoC) based fluxgate sensor.
|
|---|
