Abstract
A high-precision acceleration measurement system based on an ultra-sensitive tunnel magneto-resistance (TMR) sensor is presented in this paper. A “force–magnetic–electric” coupling structure that converts an input acceleration into a change in magnetic field around the TMR sensor is designed. In such a structure, a micro-cantilever is integrated with a magnetic field source on its tip. Under an acceleration, the mechanical displacement of the cantilever causes a change in the spatial magnetic field sensed by the TMR sensor. The TMR sensor is constructed with a Wheatstone bridge structure to achieve an enhanced sensitivity. Meanwhile, a low-noise differential circuit is developed for the proposed system to further improve the precision of the measured acceleration. The experimental results show that the micro-system achieves a measurement resolution of 19 μg/√Hz at 1 Hz, a scale factor of 191 mV/g within a range of ± 2 g, and a bias instability of 38 μg (Allan variance). The noise sources of the proposed system are thoroughly investigated, which shows that low-frequency 1/f noise is the dominant noise source. We propose to use a high-frequency modulation technique to suppress the 1/f noise effectively. Measurement results show that the 1/f noise is suppressed about 8.6-fold at 1 Hz and the proposed system resolution can be improved to 2.2 μg/√Hz theoretically with this high-frequency modulation technique.
Highlights
High-precision measurement of acceleration, which achieves ng or μg measurement resolution, is especially important in some fields such as gravity-field tests [1], navigation systems [2,3,4], seismology detection [5], and robotics [6]
(II) After photolithography, the micro-cantilever features were transferred to the (100) silicon wafer by deep reactive ion etching (DRIE). Both sides of the wafer were patterned and etched by DRIE: 3. Results and Discussion the frontside with trenches to form device features and gaps of the acceleration measurement The micro-cantilevers were fabricated with an in-house bulk micromachining process
1 Hz, corresponding to an acceleration resolution of 19 μg/ Hz at 1 Hz. These results show that the main noise source of the system in the low-frequency region was the 1/f noise of the the Cartesian coordinate system, the coordinates of the equivalent sensitive of the sensor, which limited the resolution of acceleration measurement
Summary
High-precision measurement of acceleration, which achieves ng or μg measurement resolution, is especially important in some fields such as gravity-field tests [1], navigation systems [2,3,4], seismology detection [5], and robotics [6]. A variety of methods to measure acceleration with high resolution were proposed and implemented based on principles of mechanical [7], optical [8,9], and electrical detection. The quartz flexure accelerometer measures acceleration by detecting changes in the relative position of the sensitive quartz pendulum, which has low friction torque, mechanical bias error, and temperature drift. The optical accelerometer measures the acceleration based on optical detection technology with advantages of strong anti-electromagnetic interference capability
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