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A MEMS piezoresistive sensor for measuring accelerations greater than 100,000 g (about 106 m/s2) is described in this work. To enhance the performance of the sensor, specifically widening its measurement range and natural frequency, a cross-beam construction with a center block was devised, and a Wheatstone bridge was formed by placing four piezoresistors at the ends of the fixed beams to convert acceleration into electricity. The location of the varistor was determined using the finite element approach, which yielded the optimal sensitivity. Additionally, a reliable Pt-Ti-Pt-Au electrode was designed to solve the issue of the electrode failing under high impact and enhancing the stability of the ohmic contact. The accelerometer was fabricated using MEMS technology, and the experiment with a Hopkinson pressure bar and hammering was conducted, and the bias stability was measured. It had a sensitivity of 1.06 μV/g with good linearity. The simulated natural frequency was 633 kHz The test result revealed that the accelerometer can successfully measure an acceleration of 100,000 g. [ABSTRACT FROM AUTHOR]

This paper describes the design, fabrication, and characterization of a quartz vibrating beam accelerometer consisting of a metal spring–mass and quartz double-ended tuning forks (DETFs). In this approach, the inertial force of the proof mass pulls or compresses the DETFs, affecting their resonance frequency and, thus, enabling the quasi-digital measurement of acceleration. An isolation structure was specifically designed to prevent the external interference stress from transforming into the DETFs and to decrease the DETFs' thermal stress as the ambient temperature changes. A stress-free and high-precision wire-cut electrical discharge machining process was introduced to solve the fabrication problem of flexible hinges, and a femtosecond laser was used to release the proof mass, comprehensively considering the compatibility of the fabrication process and structural design. The oscillation excitation and detection of the DETFs were analyzed, and the DETFs were fabricated using a micro-electromechanical systems process. Sensor dimensions were optimized to improve sensor sensitivity. An accelerometer prototype was fabricated, and its performance was characterized. The tested scale factor was 157.28 Hz/g, and its stability was 16.54 ppm. The bias stability and 1 g stability at 1 h were 18 and 7.84 µg, respectively. The experimental results validated the feasibility of the sensor design. [ABSTRACT FROM AUTHOR]

This study proposes a highly stable differential resonant accelerometer that is monolithically micro-machined from a piece of ultrapure, single z-cut crystal quartz. The overall structure of quartz accelerometer is centrally symmetrical, which comprises two double-ended tuning forks (DETFs), two link beams, two micro-leverages, a proof mass, and a quartz frame. Micro-leverages and DETFs are perpendicular to each other and are located around the chip, which maximizes the utilization of the sensor area and is conducive to the miniaturization of the sensor. The effectiveness of the structure was verified by theoretical analysis, simulation, and experiment. The structure with differential arrangement can eliminate common mode disturbances, such as temperature, to improve sensitivity to acceleration. Within the measurement range of ±100 g, the sensor’s sensitivity, which is measured by experiments, is 17.72 Hz/g, with a velocity random walk of 0.84 μg/√ Hz and bias instability of 3.05 μg, which is consistent with the theoretical analysis results. [2020-0309] [ABSTRACT FROM AUTHOR]

In this study, the application of micro-leverage in the monolithically all-quartz resonant accelerometer is proposed. The magnification of the micro-leverage structure used for a large size double-ended tuning fork (DETF) was analyzed. The effect of DETF's dimension both on its own force–frequency sensitivity and micro-leverage's magnification was investigated. Through the study of the relationship between DETF's force–frequency sensitivity and micro-leverage's magnification, the effect of micro-leverage and the DETF system on the sensitivity of the accelerometer was obtained. The problem of big error in theoretical calculation of micro-leverage magnification was solved because the structural arrangement of the output beam was ignored in the derivation process. The correctness of the analysis was verified by theoretical calculation, simulation, and the experiment. The equivalent structures of tension (compression) stiffness and flexural stiffness of the micro-leverage output beam were obtained by analyzing and simplifying the composite structure of the link beam and DETF. By simplifying the mechanical model of micro-leverage, the amplification factor K of micro-leverage is deduced to be 23. Therefore, the theoretical sensitivity of the sensor is 15.6 Hz/g. The experimental results show that the sensitivity of the accelerometer with the micro-leverage is 16.1 Hz/g, which is close to the theoretical analysis results. [ABSTRACT FROM AUTHOR]

This paper describes the design, fabrication, and testing of an integrated packaged sensor that is composed of a micro resonant accelerometer and a temperature sensor. The resonant accelerometer with differential configuration consists of double quartz resonators and a silicon substrate. When acceleration is applied along the sensing axis, the inertial force induced by the proof mass will transfer force to the resonators, which causes an opposite frequency shift of the dual quartz resonators. The loaded acceleration can be measured through detecting the differential frequency shift. The symmetric differential configuration response to spurious effects of thermal loading and inelastic effect causing prestress in the resonators is similar, which can be reduced by detecting the differential frequency, effectively. However, during the manufacture and packaging process, the otherness of residual stress in two quartz resonators results in that the response of resonators to temperature variation is not strictly the same. In other words, this temperature drift cannot be eliminated by the structure design. Thus, a temperature sensor and an accelerometer were packaged in a shell together. These novel integrated sensors can measure acceleration and temperature simultaneously. With the testing temperature data, a novel temperature compensation that is a combination of the variable coefficient regression and least squares support vector machine is used for improving the performance of the accelerometer. By means of this compensation and field programmable gate array, a real-time and online compensation is achieved. The tumble testing results indicate that the sensitivity of the accelerometer is ∼16.97 Hz/g. With the temperature compensation, the output drift of the scale factor is improved by 0.605 Hz/g in the full temperature range, which is from 0.072 Hz/g to 0.015 Hz/g. The drift of zero bias is improved from 345 mg to 1.9 mg. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this paper is proposed a new structure design for high performance accelerometer.Design/methodology/approach An improved sensitivity structure considering sensitivity, natural frequency and cross-axis sensitivity is established and realized. The proposed structure was designed to improve the trade-off between the sensitivity and the natural frequency of piezoresistive accelerometer and eliminate the lateral sensitivity effect by the specific configuration, which is made possible by incorporating slots into the eight-beam structure. The mechanical model and its mathematical solution are established for calculating the sensitivity and natural frequency behavior of the designed structure. The developed sensor is fabricated on the n-type single-crystal silicon wafer and packaged for experiment. The accelerometer prototype was tested in the centrifugal machine and dynamic calibration system.Findings The experimental results show that the sensitivity of the designed sensor is 0.213 mV/(Vg) and the natural frequency of the sensor is 14.22 kHz. Compared with some piezoresistive accelerometers in literatures, the designed sensor possesses a suitable characteristic in sensitivity, natural frequency and transverse effect, which allows its usage in measuring high frequency vibration signals.Originality/value The accelerometer with slotted eight-beam structure shows a good performance in the static and dynamic experiments and can be used in measuring high frequency vibration signals. [ABSTRACT FROM AUTHOR]

This paper describes a micro resonance accelerometer working in air with differential configuration using silicon spring-mass and quartz double ended tuning fork (Q-DETF) resonator. When acceleration is applied in sensing direction, the inertial force of proof mass will apply axial force on Q-DETFs, which shifts the resonance frequency of Q-DETFs. Dual Q-DETFs, working in differential condition, are bonded in the same plane at the middle of proof mass thickness along the diagonal line of square proof mass. The configuration has the advantage that the inertial force of proof mass is mostly applied along the axis of Q-DETF tines when acceleration is applied in sensing direction, and the bending of DETF induced by acceleration in sensing direction is very small so that it can be neglected, which can improve sensor nonlinearity. The highly symmetrical configuration of the sensor can better eliminate most of common-mode disturbance, especially temperature and residual stress. Theoretical analysis on sensitivity is conducted and the result matches well with experimental data. The sensor is fabricated and characterized in air using rotary experiment in earth gravitational field. In the experimental range of ±1g, the tested sensitivity, nonlinearity and hysteresis are 6.317 Hz/g, 0.26% and 0.09%, respectively. The sensor stability in 12 h is also tested in air under the influence of temperature turbulence and residual stress and the drifting of sensor output is less than 0.5 Hz. [ABSTRACT FROM AUTHOR]

Presented in this paper is the geometrical analysis and design for piezoresistive accelerometers. An improved figure of merit (FOM), considering sensitivity, resonant frequency and cross-axis sensitivity, is established to evaluate the sensor characteristics. Three conventional geometries, including cantilever-beam, quad-beam and cross-beam, are investigated to explore the influence from sensor configurations on the FOM. Based on the obtained results, a multi-beam structure is developed to provide an available solution to the drawback of low FOM in normal geometries. The proposed design increases its resonant frequency at the cost of a slight loss in sensitivity, and declines the cross-axis sensitivity by the specific configuration, which is made possible by incorporating two tiny sensing beams into the quad-beam structure. The simulated FOM is about 5.5 times of the conditional structures. The fabricated prototype is characterized for static parameters and resonant frequency. Experimental results show that the measured FOM is about 4.85 × 10 Hz, much higher than the existing designs in literatures or on the market. [ABSTRACT FROM AUTHOR]

High-g accelerometers are widely used in explosion and shock measurement. This paper describes a MEMS piezoresistive high-g accelerometer whose range is more than 50000g. It is designed on the basis of silicon on insulator (SOI) solid piezoresistive chip. The chip has a structure where both ends of the beam are fixed. Through the stress analysis and mode analysis of the accelerometer, the detailed parameters of the structure are established. The experimental results obtained from the drop hammer shock machine test and live-fire test show good properties of the accelerometer such as good output characteristic, repeatability and fast response speed. Therefore, the accelerometer in this paper meets the requirement of explosion and shock measurement basically. [ABSTRACT FROM AUTHOR]

This paper describes the design and characterization of an integrated sensor fabricated on the silicon on insulator wafer by micro electro mechanical systems technology. The integrated sensor is comprised of a tri-axis accelerometer, an absolute pressure sensor and a spreading-resistance temperature (SRT) sensor. The optimal size of the sensor structure, natural frequency and cross interference of these three sensors were simulated and determined by finite element analysis. The accelerometer with the cross structure has high sensitivity, good linearity and high response frequency proved by the static and dynamic experiments. The zero-drift, thermal zero-drift and thermal sensitivity of the accelerometer and absolute pressure sensor were also tested. The arrangement of SRT sensor with the wave structure was designed in detail. The optimal location of the SRT sensor was at the edge of chip to avoid stress interference. The integrated sensor with low cost, low mutual interference, smaller volume and good performance can be applied in mobile device, small military plane without driver and some other situations for environmental monitoring. [ABSTRACT FROM AUTHOR]

In this paper, we present a fully printed accelerometer with a piezoresistive carbon paste-based strain gauge printed on its surface, which can be manufactured at low cost and with high efficiency. This accelerometer is composed of two parts: a sensor substrate made from high-temperature resin, which is printed by a 3D printer based on stereolithography apparatus (SLA), and a carbon paste-based strain gauge fabricated by screen-printing technology and by direct ink writing (DIW) technology for the purposes of comparison and optimization. First, the structural design, theoretical analysis, simulation analysis of the accelerometer, and analyses of the conductive mechanism and the piezoresistive mechanism of the carbon paste-based strain gauge were carried out. Then the proposed accelerometer was fabricated by a combination of different printing technologies and the curing conditions of the carbon paste were investigated. After that, the accelerometers with the screen-printed strain gauge and DIW strain gauge were characterized. The results show that the printing precision of the screen-printing process on the sensor substrate is higher than the DIW process, and both accelerometers can perform acceleration measurement. Also, this kind of accelerometer can be used in the field of measuring body motion. All these findings prove that 3D printing technology is a significant method for sensor fabrication and verification. [ABSTRACT FROM AUTHOR]

A simply constructed shock tester, different from existing drop table machines, is developed for high-g level shock environment simulation. The theoretical model, structure design, and working principle of the drop tester are described. A prototype device is set up, where a carbon fiber reinforced polymer with a high specific modulus is used. Using a Brüel & Kjær high-g accelerometer, experiments to verify the validity of the design are carried out and results are given. The maximum acceleration level is in excess of 60 000 g, limited only by the manual driving force. [ABSTRACT FROM AUTHOR]

Presented in this paper is a development of a high-performance piezoresistive microaccelerometer based on the slot etching in the quad flexures for the vibration detection of high speed spindle. The proposed structure consists of a proof mass supported by four thin flexures with slots etched in the middle. Boron diffused piezoresistors located near the stress concentration regions are used for sensing the localized stress resulting from the incorporation of the slots into the flexures. Theoretical analysis and finite element analysis show satisfactory results of an improved sensitivity and favorable natural frequency higher than 10 kHz, conforming to the initial design requirements. The microfabrication techniques are described to prototype the two accelerometer chips, one with slots and the other one without slots. The tested microaccelerometers with 3 V DC power supply show an average sensitivity of 0.424 mV/g normal to the proof mass plane, increased by 60.6% than the ones without slots. An average transverse sensitivity is found to be 9.2 μV/g along X axis and 14.2 μV/g along Y axis, either of which is less than 3.5% of prime-axis sensitivity. Concerning the resonant frequency, dynamic experiment shows about 12.46 kHz and is available for the proposed design with a tiny loss of 3.5% compared with the quad-beam design. When taking the product of sensitivity and natural frequency as judgment criteria, an inspiring increase by 28.6% of the figure of merit is accomplished for the proposed accelerometer. Overall, the findings of this study confirm the feasibility of incorporating slots into the conventional configurations to improve the sensor sensitivity while maintaining a comparatively high natural frequency. [ABSTRACT FROM AUTHOR]

To improve the sensitivity and stability of a quartz vibrating beam accelerometer (QVBA), a laterally sensitive structure was developed that utilizes the force-frequency characteristics of a quartz double-ended tuning fork (DETF) to realize quasi-digital measurement of acceleration. Two DETFs were purposely designed for the sidewalls of the proof mass, and the hinge of the spring-mass structure was along the proof-mass thickness, which improved the sensitivity. Laterally sensitive structures can also solve the fabrication problems of hinges, including accuracy, deformation, and residual stress. A femtosecond laser was used to release the anchor between the out-of-frame and the proof mass to protect the hinge. The isolation structure was designed to float both the DETFs and hinge to reduce the interference of external stress. Electrodes were deposited on the four surfaces of the vibrating beam in a three-segment configuration to excite the DETF into the antiphase in-plane vibration model. As a result, an accelerometer prototype is fabricated, and the performance characterization results exhibit the sensitivity and stability of 188.61 Hz/g and 7.81 ppm, respectively, and the bias instability (Allan deviation) of 1.26 μg, which proves the design rationality of laterally sensitive QVBA. [Display omitted] • A laterally sensitive QVBA is presented, with two quartz DETFs mounted on the two sidewalls of pendulum. • The force-frequency characteristics of DETF is utilized to realize the quasi-digital measurement of acceleration. • Isolation structures are designed to suspend the hinge and DETFs from out-of-frame. • The improved sensor structure reduces machining difficulty, and a femtosecond laser is used to release the hinge. • The sensitivity and its stability are 188.61 Hz/g and 7.81 ppm, respectively, and the bias instability is 1.26 μg. [ABSTRACT FROM AUTHOR]

A novel piezoresistive accelerometer was developed with high performance in sensitivity, resonant frequency and cross-axis sensitivity. The accelerometer chip with axially stressed self-supporting sensing beams has been designed, fabricated and tested in our study. We derived the expressions for the location of the sensing beams, stresses and resonant frequency, and then these results were verified by the finite element method (FEM) simulation. The fabricated accelerometer was characterized by the static and dynamic experiments. The results showed that the measuring sensitivity was 0.666 mV/g/3 V and the resonant frequency was 17.1 kHz. Meanwhile, the proposed accelerometer provided an available method for the low cross-axis sensitivity design. Compared with other accelerometers in the literatures, the developed accelerometer exhibited an excellent performance concerning a comprehensive figure of merit (FOM). The results demonstrated the feasibility of the novel structure to improve the accelerometer’s performance. [ABSTRACT FROM AUTHOR]