High-Precision Acceleration Measurement System Based on Tunnel Magneto-Resistance Effect

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.

Design, Analysis and Simulation of a MEMS-Based Gyroscope with Differential Tunneling Magnetoresistance Sensing Structure

“…Compared with the TMR gyroscope in Literature [ 18 ] with a noise floor of 9.48 × 10 −5 °/s/ , that of our design reduced by 12.29 times. Simultaneously, the magnetic film used in Literature [ 17 , 21 ] has a mT-level MII and a mT/mm-level magnetic sensitivity, while the permanent magnet used in Literature [ 18 , 22 ] have a T-level MII and an oe/um-level magnetic sensitivity. All of them require a large-range TMR unit to detect the variation of magnetic field such as TMR 2105 and TMR P44FP, or a higher detection gap.…”

“…The experimental results indicated that the final sensitivities of the two devices are 409.01 mV/g and 8.85mV/g, respectively. Literature [ 22 ] reported another accelerometer with the similar operating principle to ones from [ 17 , 21 ]. The peculiarity of latter one is the use of the simpler but more effective micro-cantilever sensing structure, and the test results demonstrated the system could achieve measurement resolution of 17.35 µg/ .…”

Tunneling Magnetoresistance DC Current Transformer for Ion Beam Diagnostics

“…Recent developments in magnetic field sensor fabrication technologies introduced new IC types of magnetic field sensors that can be used in contactless current transducers. These sensors are based on the MR (Magnetoresistance) effect [ 11 , 12 , 13 ]. MR IC sensors are used for low magnetic field detection since their sensitivities are extremely high, but they saturate at low magnetic field levels compared to Hall sensors [ 4 , 11 , 12 , 13 ].…”