With the recent development of digital Micro Electro Mechanical System （MEMS） sensors, the cost of monitoring and detecting seismic events in real time can be greatly reduced. Ability of MEMS accelerograph to record...With the recent development of digital Micro Electro Mechanical System （MEMS） sensors, the cost of monitoring and detecting seismic events in real time can be greatly reduced. Ability of MEMS accelerograph to record a seismic event depends upon the efficiency of triggering algorithm, apart from the sensor＇s sensitivity. There are several classic triggering algorithms developed to detect seismic events, ranging from basic amplitude threshold to more sophisticated pattern recognition. Algorithms based on STA/LTA are reported to be computationally efficient for real time monitoring. In this paper, we analyzed several STA/LTA algorithms to check their efficiency and suitability using data obtained from the Quake Catcher Network （network of MEMS accelerometer stations）. We found that most of the STA/LTA algorithms are suitable for use with MEMS accelerometer data to accurately detect seismic events. However, the efficiency of any particular algorithm is found to be dependent on the parameter set used （i.e., window width of STA, LTA and threshold level）.展开更多
In the past,only one performance parameter was considered in the reliability estimation of micro-electro-mechanical system (MEMS) accelerometers,resulting in a one-sided reliability evaluation. Aiming at the failure c...In the past,only one performance parameter was considered in the reliability estimation of micro-electro-mechanical system (MEMS) accelerometers,resulting in a one-sided reliability evaluation. Aiming at the failure condition of large range MEMS accelerometers in high temperature environment,the corresponding accelerated degradation test is designed. According to the degradation condition of zero bias and scale factor,multiple dependent reliability estimation of large range MEMS accelerometers is carried out. The results show that the multiple dependent reliability estimation of the large range MEMS accelerometers can improve the accuracy of the estimation and get more accurate results.展开更多
A new scheme is proposed to model 3D angular motion of a revolving regular object with miniature, low-cost micro electro mechanical systems(MEMS) accelerometers(instead of gyroscope),which is employed in 3D mouse syst...A new scheme is proposed to model 3D angular motion of a revolving regular object with miniature, low-cost micro electro mechanical systems(MEMS) accelerometers(instead of gyroscope),which is employed in 3D mouse system.To sense 3D angular motion,the static property of MEMS accelerometer,sensitive to gravity acceleration,is exploited.With the three outputs of configured accelerometers,the proposed model is implemented to get the rotary motion of the rigid object.In order to validate the effectiveness of the proposed model,an input device is developed with the configuration of the scheme.Experimental results show that a simulated 3D cube can accurately track the rotation of the input device.The result indicates the feasibility and effectiveness of the proposed model in the 3D mouse system.展开更多
Anti-spring mechanisms are widely used for improving the noise performance of MEMS accelerometers due to their stiffness softening effect.However,the existing mechanisms typically require large bias force and displace...Anti-spring mechanisms are widely used for improving the noise performance of MEMS accelerometers due to their stiffness softening effect.However,the existing mechanisms typically require large bias force and displacement for achieving stiffness softening,leading to large device dimensions.Here,we propose a novel anti-spring mechanism composed of two pre-shaped curved beams connected in a parallel configuration,which can achieve stiffness softening without requiring large bias force and displacement.The stiffness softening effect of the mechanism is verified through theoretical modeling and finite element method(FEM)simulation.After that,the mechanism is implemented in a 4.2 mm×4.9 mm MEMS capacitive accelerometer prototype.The experimental results reveal that the sensitivity of the accelerometer increases by 10.4%compared to the initial sensitivity;at the same time,the noise floor and bias instability decrease by 10.5%and 4.2%.The sensitivity,nonlinearity,bias instability,and noise floor after biasing are 51.1 mV/g,0.99%,0.24 mg,and 21.3μg=√Hz p,respectively.Thus,the proposed mechanism can enhance the performance of the accelerometer.This work provides an innovative approach for improving the performance of MEMS accelerometers while enabling miniaturization.展开更多
This paper reports an approach of in-operation temperature bias drift compensation based on phase-based calibration for a stiffness-tunable MEMS accelerometer with double-sided parallel plate(DSPP)capacitors.The tempe...This paper reports an approach of in-operation temperature bias drift compensation based on phase-based calibration for a stiffness-tunable MEMS accelerometer with double-sided parallel plate(DSPP)capacitors.The temperature drifts of the components of the accelerometer are characterized,and analytical models are built on the basis of the measured drift results.Results reveal that the temperature drift of the acceleration output bias is dominated by the sensitive mechanical stiffness.An out-of-bandwidth AC stimulus signal is introduced to excite the accelerometer,and the interference with the acceleration measurement is minimized.The demodulated phase of the excited response exhibits a monotonic relationship with the effective stiffness of the accelerometer.Through the proposed online compensation approach,the temperature drift of the effective stiffness can be detected by the demodulated phase and compensated in real time by adjusting the stiffness-tuning voltage of DSPP capacitors.The temperature drift coefficient(TDC)of the accelerometer is reduced from 0.54 to 0.29 mg/℃,and the Allan variance bias instability of about 2.8μg is not adversely affected.Meanwhile,the pull-in resulting from the temperature drift of the effective stiffness can be prevented.TDC can be further reduced to 0.04 mg/℃through an additional offline calibration based on the demodulated carrier phase representing the temperature drift of the readout circuit.展开更多
Resonant accelerometer is designed,which includes two double-ended tuning forks,a proof mass,four-leverage system amplifying inertial force,and drive/sense combs.Each tuning fork is electrostatically actuated and sens...Resonant accelerometer is designed,which includes two double-ended tuning forks,a proof mass,four-leverage system amplifying inertial force,and drive/sense combs.Each tuning fork is electrostatically actuated and sensed at resonance using comb electrodes.The device is fabricated using MEMS bulk-silicon technology,whose sensitive degree is 27 3Hz/g,and the resolution is 167 8μg.展开更多
This study introduces a MEMS accelerometer equipped with an adaptive tuning system for an electrostatic anti-spring.As the input acceleration increases,the sensitivity of the adaptive MEMS accelerometer decreases to c...This study introduces a MEMS accelerometer equipped with an adaptive tuning system for an electrostatic anti-spring.As the input acceleration increases,the sensitivity of the adaptive MEMS accelerometer decreases to compensate for the measurement range.It leverages the benefits of both conventional open-and closed-loop accelerometer designs.Comprehensive theoretical analyses and experimental tests are conducted,showing consistency between theory and experimental results.In comparison to conventional MEMS accelerometer designs,this novel MEMS accelerometer demonstrates enhanced performance.With an actuation voltage of 15.4 V and under 0 g acceleration input,the sensitivity of the accelerometer improves from 1.28 V/g to 39.43 V/g,and the spring constant is reduced from 41.0 N/m to 1.38 N/m.The noise floor also decreases from 8628 ng/√Hz(at 100 Hz)to 279 ng/√Hz(at 100 Hz).The dynamic range enhances from 127 dB to 157 dB.Besides,a hybrid continuous-time interface is utilized to apply the actuation force on the sensing comb fingers.This approach not only simplifies the circuit design but also minimizes the required die area,power consumption.The combination of these features makes the novel MEMS accelerometer both highly sensitive and large measurement range,as a promising solution for various applications.展开更多
We present a bulk micromachined in-plane capacitive accelerometer fabricated with an improved process flow,by etching only one-fifth of the wafer thickness at the back of the silicon while forming the bar-structure el...We present a bulk micromachined in-plane capacitive accelerometer fabricated with an improved process flow,by etching only one-fifth of the wafer thickness at the back of the silicon while forming the bar-structure electrode for the sensing capacitor.The improved flow greatly lowers the footing effect during deep reactive ion etching(DRIE),and increases the proof mass by 54% compared to the traditional way,resulting in both improved device quality and a higher yield rate.Acceleration in the X direction is sensed capacitively by varying the overlapped area of a differential capacitor pair,which eliminates the nonlinear behavior by fixing the parallel-plate gap.The damping coefficient of the sensing motion is low due to the slide-film damping.A large proof mass is made using DRIE,which also ensures that dimensions of the spring beams in the Y and Z directions can be made large to lower cross axis coupling and increase the pull-in voltage.The theoretical Brownian noise floor is 0.47 μg/Hz1/2 at room temperature and atmospheric pressure.The tested frequency response of a prototype complies with the low damping design scheme.Output data for input acceleration from ?1 g to 1 g are recorded by a digital multimeter and show very good linearity.The tested random bias of the prototype is 130 μg at an averaging time of around 6 s.展开更多
The noise of closed loop micro-electromechanical systems(MEMS) capacitive accelerometer is treated as one of the significant performance specifications.Traditional optimization of noise performance often focuses on de...The noise of closed loop micro-electromechanical systems(MEMS) capacitive accelerometer is treated as one of the significant performance specifications.Traditional optimization of noise performance often focuses on designing large capacitive sensitivity accelerometer and applying closed loop structure to shape total noise,but different noise sources in closed loop and their behaviors at low frequencies are seldom carefully studied,especially their behaviors with different electronic parameters.In this work,a thorough noise analysis is established focusing on the four noise sources transfer functions near 0 Hz with simplified electronic parameters in closed loop,and it is found that the total electronic noise equivalent acceleration varies differently at different frequency points,such that the noise spectrum shape at low frequencies can be altered from 1/f noise-like shape to flat spectrum shape.The bias instability changes as a consequence.With appropriate parameters settings,the 670 Hz resonant frequency accelerometer can reach resolution of 2.6 μg/(Hz)1/2 at 2 Hz and 6 μg bias instability,and 1300 Hz accelerometer can achieve 5μg/(Hz)1/2 at 2 Hz and 31 μg bias instability.Both accelerometers have flat spectrum profile from 2 Hz to 15 Hz.展开更多
The bias drift of a micro-electro-mechanical systems （MEMS） accelerometer suffers from the l/f noise and the tem- perature effect. For massive applications, the bias drift urgently needs to be improved. Conventional...The bias drift of a micro-electro-mechanical systems （MEMS） accelerometer suffers from the l/f noise and the tem- perature effect. For massive applications, the bias drift urgently needs to be improved. Conventional methods often cannot ad- dress the l/f noise and temperature effect in one architecture. In this paper, a combined approach on closed-loop architecture modification is proposed to minimize the bias drift. The modulated feedback approach is used to isolate the l/f noise that exists in the conventional direct feedback approach. Then a common mode signal is created and added into the closed loop on the basis of modulated feedback architecture, to compensate for the temperature drift. With the combined approach, the bias instability is improved to less than 13 μg, and the drift of the Allan variance result is reduced to 17 μg at 100 s of the integration time. The temperature coefficient is reduced from 4.68 to 0.1 mg/℃. The combined approach could be useful for many other closed-loop accelerometers.展开更多
A high stability in-circuit reprogrammable technique control system for a capacitive MEMS accelerometer is presented. Modulation and demodulation are used to separate the signal from the low frequency noise. A low-noi...A high stability in-circuit reprogrammable technique control system for a capacitive MEMS accelerometer is presented. Modulation and demodulation are used to separate the signal from the low frequency noise. A low-noise low-offset charge integrator is employed in this circuit to implement a capacitance-to-voltage converter and minimize the noise and offset. The application-specific integrated circuit （ASIC） is fabricated in a 0.5 /μm one-ploy three-metal CMOS process. The measured results of the proposed circuit show that the noise floor of the ASIC is -116 dBV, the sensitivity of the accelerometer is 66 mV/g with a nonlinearity of 0.5%. The chip occupies 3.5×2.5 mm2 and the current is 3.5 mA.展开更多
This paper proposes a differential mode measurement and control system(DMCS)for differential MEMS resonant accelerometer(DMRA),which operates the differential resonators of the DMRA at different vibration modes.Unlike...This paper proposes a differential mode measurement and control system(DMCS)for differential MEMS resonant accelerometer(DMRA),which operates the differential resonators of the DMRA at different vibration modes.Unlike traditional DMRA,the first resonator of the differential resonator operates in the first-order mode(R1M1),and the second resonator operates in the second-order mode(R2M2).Within the measurement range of DMRA,the frequencies of the two resonators will not cross,so there will be no mutual interference.This ensures the structural symmetry of the DMRA while avoiding the measurement dead zone phenomenon caused by the coupling of the differential vibration beam at similar resonant frequencies.The structural symmetry of the differential resonator ensures good temperature consistency of the differential vibration beam,and the consistency of the temperature frequency coefficient matches well,which enables the differential resonator to strongly suppress the temperatureinduced common-mode effects.During the temperature cycling process between-20℃ and 80℃,the equivalent acceleration drift of R1M1 and R2M2 were 341.6 mg and 414.6 mg,respectively.After using the differential temperature compensation algorithm,the equivalent acceleration drift was reduced to 1.19 mg.The minimum Allan variance measured statically at room temperature decreased from 1.42μg@0.85 s for R1M1 and 1.52μg@0.85 s for R2M2 to 0.23μg@7.15 s,indicating a significant improvement in the long-term stability of DMRA.In addition,the differential measuring method also eliminated common mode ambient noise in low frequency range,ultimately achieving a noise level of 220 ng=ffiffiffiffiffi Hz p@(0.2–0.8 Hz)for a prototype device with a measurement range exceeding±5 g.展开更多
基金IIT Roorkee under the Faculty Initiation Grant No.100556
文摘With the recent development of digital Micro Electro Mechanical System （MEMS） sensors, the cost of monitoring and detecting seismic events in real time can be greatly reduced. Ability of MEMS accelerograph to record a seismic event depends upon the efficiency of triggering algorithm, apart from the sensor＇s sensitivity. There are several classic triggering algorithms developed to detect seismic events, ranging from basic amplitude threshold to more sophisticated pattern recognition. Algorithms based on STA/LTA are reported to be computationally efficient for real time monitoring. In this paper, we analyzed several STA/LTA algorithms to check their efficiency and suitability using data obtained from the Quake Catcher Network （network of MEMS accelerometer stations）. We found that most of the STA/LTA algorithms are suitable for use with MEMS accelerometer data to accurately detect seismic events. However, the efficiency of any particular algorithm is found to be dependent on the parameter set used （i.e., window width of STA, LTA and threshold level）.
文摘In the past,only one performance parameter was considered in the reliability estimation of micro-electro-mechanical system (MEMS) accelerometers,resulting in a one-sided reliability evaluation. Aiming at the failure condition of large range MEMS accelerometers in high temperature environment,the corresponding accelerated degradation test is designed. According to the degradation condition of zero bias and scale factor,multiple dependent reliability estimation of large range MEMS accelerometers is carried out. The results show that the multiple dependent reliability estimation of the large range MEMS accelerometers can improve the accuracy of the estimation and get more accurate results.
文摘A new scheme is proposed to model 3D angular motion of a revolving regular object with miniature, low-cost micro electro mechanical systems(MEMS) accelerometers(instead of gyroscope),which is employed in 3D mouse system.To sense 3D angular motion,the static property of MEMS accelerometer,sensitive to gravity acceleration,is exploited.With the three outputs of configured accelerometers,the proposed model is implemented to get the rotary motion of the rigid object.In order to validate the effectiveness of the proposed model,an input device is developed with the configuration of the scheme.Experimental results show that a simulated 3D cube can accurately track the rotation of the input device.The result indicates the feasibility and effectiveness of the proposed model in the 3D mouse system.
基金supported by the National Key Research and Development Program of China Nos.2022YFB3205000,2022YFB3205004,and 2024YFB3614100the National Natural Science Foundation of China(NSFC)61974156+1 种基金the Foundation of the Key State Laboratory of Transducer Technology SKT2303Jiangsu Provincial Key Research and Development program BE2023048.
文摘Anti-spring mechanisms are widely used for improving the noise performance of MEMS accelerometers due to their stiffness softening effect.However,the existing mechanisms typically require large bias force and displacement for achieving stiffness softening,leading to large device dimensions.Here,we propose a novel anti-spring mechanism composed of two pre-shaped curved beams connected in a parallel configuration,which can achieve stiffness softening without requiring large bias force and displacement.The stiffness softening effect of the mechanism is verified through theoretical modeling and finite element method(FEM)simulation.After that,the mechanism is implemented in a 4.2 mm×4.9 mm MEMS capacitive accelerometer prototype.The experimental results reveal that the sensitivity of the accelerometer increases by 10.4%compared to the initial sensitivity;at the same time,the noise floor and bias instability decrease by 10.5%and 4.2%.The sensitivity,nonlinearity,bias instability,and noise floor after biasing are 51.1 mV/g,0.99%,0.24 mg,and 21.3μg=√Hz p,respectively.Thus,the proposed mechanism can enhance the performance of the accelerometer.This work provides an innovative approach for improving the performance of MEMS accelerometers while enabling miniaturization.
基金The work is supported by the Grant of the National Natural Science Foundation of China(Grant No.62104211).
文摘This paper reports an approach of in-operation temperature bias drift compensation based on phase-based calibration for a stiffness-tunable MEMS accelerometer with double-sided parallel plate(DSPP)capacitors.The temperature drifts of the components of the accelerometer are characterized,and analytical models are built on the basis of the measured drift results.Results reveal that the temperature drift of the acceleration output bias is dominated by the sensitive mechanical stiffness.An out-of-bandwidth AC stimulus signal is introduced to excite the accelerometer,and the interference with the acceleration measurement is minimized.The demodulated phase of the excited response exhibits a monotonic relationship with the effective stiffness of the accelerometer.Through the proposed online compensation approach,the temperature drift of the effective stiffness can be detected by the demodulated phase and compensated in real time by adjusting the stiffness-tuning voltage of DSPP capacitors.The temperature drift coefficient(TDC)of the accelerometer is reduced from 0.54 to 0.29 mg/℃,and the Allan variance bias instability of about 2.8μg is not adversely affected.Meanwhile,the pull-in resulting from the temperature drift of the effective stiffness can be prevented.TDC can be further reduced to 0.04 mg/℃through an additional offline calibration based on the demodulated carrier phase representing the temperature drift of the readout circuit.
文摘Resonant accelerometer is designed,which includes two double-ended tuning forks,a proof mass,four-leverage system amplifying inertial force,and drive/sense combs.Each tuning fork is electrostatically actuated and sensed at resonance using comb electrodes.The device is fabricated using MEMS bulk-silicon technology,whose sensitive degree is 27 3Hz/g,and the resolution is 167 8μg.
基金funded by The Science and Technology Development Fund,Macao SAR(FDCT),004/2023/SKLNational Natural Science Foundation of China(No.42204182)Knowledge Innovation Program of Wuhan-Basic Research(No.2023010201010042).
文摘This study introduces a MEMS accelerometer equipped with an adaptive tuning system for an electrostatic anti-spring.As the input acceleration increases,the sensitivity of the adaptive MEMS accelerometer decreases to compensate for the measurement range.It leverages the benefits of both conventional open-and closed-loop accelerometer designs.Comprehensive theoretical analyses and experimental tests are conducted,showing consistency between theory and experimental results.In comparison to conventional MEMS accelerometer designs,this novel MEMS accelerometer demonstrates enhanced performance.With an actuation voltage of 15.4 V and under 0 g acceleration input,the sensitivity of the accelerometer improves from 1.28 V/g to 39.43 V/g,and the spring constant is reduced from 41.0 N/m to 1.38 N/m.The noise floor also decreases from 8628 ng/√Hz(at 100 Hz)to 279 ng/√Hz(at 100 Hz).The dynamic range enhances from 127 dB to 157 dB.Besides,a hybrid continuous-time interface is utilized to apply the actuation force on the sensing comb fingers.This approach not only simplifies the circuit design but also minimizes the required die area,power consumption.The combination of these features makes the novel MEMS accelerometer both highly sensitive and large measurement range,as a promising solution for various applications.
基金Project(No.NCET-06-0514)supported by the Program for New Century Excellent Talents in University,China
文摘We present a bulk micromachined in-plane capacitive accelerometer fabricated with an improved process flow,by etching only one-fifth of the wafer thickness at the back of the silicon while forming the bar-structure electrode for the sensing capacitor.The improved flow greatly lowers the footing effect during deep reactive ion etching(DRIE),and increases the proof mass by 54% compared to the traditional way,resulting in both improved device quality and a higher yield rate.Acceleration in the X direction is sensed capacitively by varying the overlapped area of a differential capacitor pair,which eliminates the nonlinear behavior by fixing the parallel-plate gap.The damping coefficient of the sensing motion is low due to the slide-film damping.A large proof mass is made using DRIE,which also ensures that dimensions of the spring beams in the Y and Z directions can be made large to lower cross axis coupling and increase the pull-in voltage.The theoretical Brownian noise floor is 0.47 μg/Hz1/2 at room temperature and atmospheric pressure.The tested frequency response of a prototype complies with the low damping design scheme.Output data for input acceleration from ?1 g to 1 g are recorded by a digital multimeter and show very good linearity.The tested random bias of the prototype is 130 μg at an averaging time of around 6 s.
基金Project(61404122)supported by the National Natural Science Foundation of China
文摘The noise of closed loop micro-electromechanical systems(MEMS) capacitive accelerometer is treated as one of the significant performance specifications.Traditional optimization of noise performance often focuses on designing large capacitive sensitivity accelerometer and applying closed loop structure to shape total noise,but different noise sources in closed loop and their behaviors at low frequencies are seldom carefully studied,especially their behaviors with different electronic parameters.In this work,a thorough noise analysis is established focusing on the four noise sources transfer functions near 0 Hz with simplified electronic parameters in closed loop,and it is found that the total electronic noise equivalent acceleration varies differently at different frequency points,such that the noise spectrum shape at low frequencies can be altered from 1/f noise-like shape to flat spectrum shape.The bias instability changes as a consequence.With appropriate parameters settings,the 670 Hz resonant frequency accelerometer can reach resolution of 2.6 μg/(Hz)1/2 at 2 Hz and 6 μg bias instability,and 1300 Hz accelerometer can achieve 5μg/(Hz)1/2 at 2 Hz and 31 μg bias instability.Both accelerometers have flat spectrum profile from 2 Hz to 15 Hz.
文摘The bias drift of a micro-electro-mechanical systems （MEMS） accelerometer suffers from the l/f noise and the tem- perature effect. For massive applications, the bias drift urgently needs to be improved. Conventional methods often cannot ad- dress the l/f noise and temperature effect in one architecture. In this paper, a combined approach on closed-loop architecture modification is proposed to minimize the bias drift. The modulated feedback approach is used to isolate the l/f noise that exists in the conventional direct feedback approach. Then a common mode signal is created and added into the closed loop on the basis of modulated feedback architecture, to compensate for the temperature drift. With the combined approach, the bias instability is improved to less than 13 μg, and the drift of the Allan variance result is reduced to 17 μg at 100 s of the integration time. The temperature coefficient is reduced from 4.68 to 0.1 mg/℃. The combined approach could be useful for many other closed-loop accelerometers.
文摘A high stability in-circuit reprogrammable technique control system for a capacitive MEMS accelerometer is presented. Modulation and demodulation are used to separate the signal from the low frequency noise. A low-noise low-offset charge integrator is employed in this circuit to implement a capacitance-to-voltage converter and minimize the noise and offset. The application-specific integrated circuit （ASIC） is fabricated in a 0.5 /μm one-ploy three-metal CMOS process. The measured results of the proposed circuit show that the noise floor of the ASIC is -116 dBV, the sensitivity of the accelerometer is 66 mV/g with a nonlinearity of 0.5%. The chip occupies 3.5×2.5 mm2 and the current is 3.5 mA.
基金supported in part by the National Key Research and Development Program of China under Grant 2022YFB3207301Shandong Provincial Natural Science Foundation under Grant No.ZR2024ZD08.
文摘This paper proposes a differential mode measurement and control system(DMCS)for differential MEMS resonant accelerometer(DMRA),which operates the differential resonators of the DMRA at different vibration modes.Unlike traditional DMRA,the first resonator of the differential resonator operates in the first-order mode(R1M1),and the second resonator operates in the second-order mode(R2M2).Within the measurement range of DMRA,the frequencies of the two resonators will not cross,so there will be no mutual interference.This ensures the structural symmetry of the DMRA while avoiding the measurement dead zone phenomenon caused by the coupling of the differential vibration beam at similar resonant frequencies.The structural symmetry of the differential resonator ensures good temperature consistency of the differential vibration beam,and the consistency of the temperature frequency coefficient matches well,which enables the differential resonator to strongly suppress the temperatureinduced common-mode effects.During the temperature cycling process between-20℃ and 80℃,the equivalent acceleration drift of R1M1 and R2M2 were 341.6 mg and 414.6 mg,respectively.After using the differential temperature compensation algorithm,the equivalent acceleration drift was reduced to 1.19 mg.The minimum Allan variance measured statically at room temperature decreased from 1.42μg@0.85 s for R1M1 and 1.52μg@0.85 s for R2M2 to 0.23μg@7.15 s,indicating a significant improvement in the long-term stability of DMRA.In addition,the differential measuring method also eliminated common mode ambient noise in low frequency range,ultimately achieving a noise level of 220 ng=ffiffiffiffiffi Hz p@(0.2–0.8 Hz)for a prototype device with a measurement range exceeding±5 g.
