Sensitivity Of Accelerometer Research Articles

Modeling Electronic Devices with a Casimir Cavity

The Casimir effect has been exploited in various MEMS (micro-electro-mechanical system) devices, especially to make sensitive force sensors and accelerometers. It has also been used to provide forces for a variety of purposes, for example, for the assembly of considerably small parts. Repulsive forces and torques have been produced using various configurations of media and materials. Just a few electronic devices have been explored that utilize the electrical properties of the Casimir effect. Recently, experimental results were presented that described the operation of an electronic device that employed a Casimir cavity attached to a standard MIM (metal–insulator–metal) structure. The DC (direct current) conductance of the novel MIM device was enhanced by the attached cavity and found to be directly proportional to the capacitance of the attached cavity. The phenomenological model proposed assumed that the cavity reduced the vacuum fluctuations, which resulted in a reduced injection of carriers. The analysis presented here indicates that the optical cavity actually enhances vacuum fluctuations, which would predict a current in the opposite direction from that observed. Further, the vacuum fluctuations near the electrode are shown to be approximately independent of the size of the optical cavity, in disagreement with the experimental data which show a dependence on the size. Thus, the proposed mechanism of operation does not appear correct. A more detailed theoretical analysis of these devices is needed, in particular, one that uses real material parameters and computes the vacuum fluctuations for the entire device. Such an analysis would reveal how these devices operate and might suggest design principles for a new genre of electronic devices that make use of vacuum fluctuations.

Study on the influence of manufacturing tolerance of the spring beam on the sensitivity of the two-axis MEMS accelerometer

Study on the influence of manufacturing tolerance of the spring beam on the sensitivity of the two-axis MEMS accelerometer

A self-powered accelerometer with over-range detection for vibration and shock based on triboelectric-electromagnetic mechanism

Accelerometers based on triboelectric nanogenerators (TENGs) have garnered significant interest in recent years. However, many of these devices lack a self-sustained power supply for autonomous wireless operations and a mechanism for over-range detection. Additionally, theoretical investigations on the sensitivity of TENG-based accelerometers are scarce. In this work, a novel self-powered accelerometer for vibration and shock integrating a freestanding triboelectric-layer-based TENG (FT-TENG), two contact-separation TENGs (CS-TENGs) and an electromagnetic generator (EMG) is proposed and then investigated through both numerical simulations and experimental demonstrations. The EMG is used for vibration energy harvesting, exhibiting an impressive power output of 4.11 mW under a vibration acceleration of 12 m/s2. The FT-TENG and the CS-TENGs work for acceleration sensing and over-range detection respectively. Under vibration, the sensitivity and measurement range are related to the frequency of excitation, and the proposed accelerometer has the maximum sensitivity (0.75 V s2/m) at its natural frequency. For shock events, the sensitivity of the accelerometer is dominated by the shock duration in a short-duration range, which is estimated to be 0.12 V s2/m under a shock duration of 0.03 s. This work not only contributes to the understanding of TENGs adopted for sensing but also creates potential applications of triboelectric and electromagnetic energy harvesting and provides a feasible design for autonomous wireless sensor nodes.

Dependence of Structural Design on Effective Young's Modulus of Ti/Au Multi-layered Micro-cantilevers

Gold-based micro-electro-mechanical-systems (Au-MEMS) capacitive accelerometers can simultaneously realize high sensitivity and miniaturization because of the high mass density of Au. In order to further improve the sensitivity of the Au-MEMS capacitive accelerometers, Young's modulus of the cantilever-like spring part connected to the movable component is a key parameter. Considering the size effect in the mechanical property of metallic materials on micro-scale, the design of the spring part is expected to reflect their Young's modulus; that is, effective Young's modulus (Eeff). In this study, we clarify effects of the structural designs of the Au-based micro-cantilevers on their Eeff by experiments and finite element analyses (FEA) simulations. The Eeff of the Au micro-cantilevers having Ti/Au multi-layered structures is evaluated by resonance frequency method, which demonstrates the key structural parameters affecting their Eeff. The FEA calculations show a consistent trend with that observed in the experimental results.

Reliability and Sensitivity of Smartphone Accelerometer to Assess Postural Balance in Healthy Individuals

Reliability and Sensitivity of Smartphone Accelerometer to Assess Postural Balance in Healthy Individuals

Experimental characterization of a mode-localized acceleration sensor integrating electrostatically coupled resonators

A novel mode-localized acceleration sensor employing an electrostatically coupled resonator and integrating a lever with proof mass is micromachined using standard silicon on insulator (SOI) technology. In order to determine the linear dynamic range of the sensor, a reduced order model is developed while assuming that the resonators vibrate below the critical amplitude. Then, open-loop and closed-loop testing platforms are established to measure the performance of the linearly operating accelerometer in a vacuum environment (less than 5 Pa). Moreover, the corresponding amplifier circuit based on the capacitive detection principle is designed in order to extract and amplify the current signal from the resonators. The obtained results show that the accelerometer sensitivity can be increased by three orders of magnitude when using the relative shift of amplitude ratio as the output metric instead of the relative shift of frequency, and the experimental measurements are consistent with the theoretical predictions. Remarkably, the Allan standard deviation of the mode-localized acceleration sensor obtained from the closed-loop testing circuit is around 5.03 μg.

An Accelerometer-Based Wearable Patch for Robust Respiratory Rate and Wheeze Detection Using Deep Learning.

Wheezing is a critical indicator of various respiratory conditions, including asthma and chronic obstructive pulmonary disease (COPD). Current diagnosis relies on subjective lung auscultation by physicians. Enabling this capability via a low-profile, objective wearable device for remote patient monitoring (RPM) could offer pre-emptive, accurate respiratory data to patients. With this goal as our aim, we used a low-profile accelerometer-based wearable system that utilizes deep learning to objectively detect wheezing along with respiration rate using a single sensor. The miniature patch consists of a sensitive wideband MEMS accelerometer and low-noise CMOS interface electronics on a small board, which was then placed on nine conventional lung auscultation sites on the patient's chest walls to capture the pulmonary-induced vibrations (PIVs). A deep learning model was developed and compared with a deterministic time-frequency method to objectively detect wheezing in the PIV signals using data captured from 52 diverse patients with respiratory diseases. The wearable accelerometer patch, paired with the deep learning model, demonstrated high fidelity in capturing and detecting respiratory wheezes and patterns across diverse and pertinent settings. It achieved accuracy, sensitivity, and specificity of 95%, 96%, and 93%, respectively, with an AUC of 0.99 on the test set-outperforming the deterministic time-frequency approach. Furthermore, the accelerometer patch outperforms the digital stethoscopes in sound analysis while offering immunity to ambient sounds, which not only enhances data quality and performance for computational wheeze detection by a significant margin but also provides a robust sensor solution that can quantify respiration patterns simultaneously.

Investigation of New Accelerometer Based on Capacitive Micromachined Ultrasonic Transducer (CMUT) with Ring-Perforation Membrane.

Capacitive micromachined ultrasonic transducer (CMUT) has been widely studied due to its excellent resonance characteristics and array integration. This paper presents the first study of the CMUT electrostatic stiffness resonant accelerometer. To improve the sensitivity of the CMUT accelerometer, this paper innovatively proposes the CMUT ring-perforation membrane structure, which effectively improves the acceleration sensitivity by reducing the mechanical stiffness of the elastic membrane. The acceleration sensitivity is 10.9 (Hz/g) in the acceleration range of 0-20 g, which is 100% higher than that of the conventional CMUT structure. This research contributes to the acceleration measurement field of CMUT and can effectively contribute to the breakthrough of vibration acceleration monitoring technology in aerospace, medical equipment, and automotive electronics.

Characterization of Sensitivity of Time Domain MEMS Accelerometer.

This paper characterizes the sensitivity of a time domain MEMS accelerometer. The sensitivity is defined by the increment in the measured time interval per gravitational acceleration. Two sensitivities exist, and they can be enhanced by decreasing the amplitude and frequency. The sensitivity with minor nonlinearity is chosen to evaluate the time domain sensor. The experimental results of the developed accelerometer demonstrate that the sensitivities span from -68.91 μs/g to -124.96 μs/g and the 1σ noises span from 8.59 mg to 6.2 mg (amplitude of 626 nm: -68.91 μs/g and 10.21 mg; amplitude of 455 nm: -94.51 μs/g and 7.76 mg; amplitude of 342 nm: -124.96 μs/g and 6.23 mg), which indicates the bigger the amplitude, the smaller the sensitivity and the bigger the 1σ noise. The adjustable sensitivity provides a theoretical foundation for range self-adaption, and all the results can be extended to other time domain inertial sensors, e.g., a gyroscope or an inclinometer.

(Invited) Mechanical Property Design of Multilayered Ti/Au Microcomponents by Electrodeposition Toward High-Sensitive MEMS Accelerometers

Recently, MEMS accelerometers employing Au components prepared by electrodeposition are reported to have a small size whiling retaining a high sensitivity [1], which is mainly contribute by Au’s high mass density, as shown in Fig. 1. Detections of body tremors and muscular sounds are realized using this highly sensitive MEMS accelerometer [2]. However, low mechanical strength of Au, when compared to Si-based materials commonly used in conventional MEMS accelerometers, leads to insufficient structure stability for the long-term use of the device. To enhance the mechanical strength of Au-based materials, several approaches have been reported; for example, multi-layered metal technology [3], and alloying Au with Cu [4]. On the other hand, effects of such approaches on the long-term structure stability of the Au-based materials with dimensions in micro-scale remain uncleared. Considering the relationship between mechanical properties of metallic materials and size of the specimens evaluated, evaluation of the long-term structure stability of Au-based materials in micro-scare is essential for commercial uses of the Au-based MEMS device.Cantilever-like structures are commonly used in movable components in MEMS devices [1, 3]. Repeatedly electrodeposition of gold following by deposition of a material with a high mechanical strength to realize a multi-layered structure is an effective strategy to enhance the structural stability [5]. From the Euler-Bernoulli beam theory, the structural stability of a cantilever-like structure is improved by using materials having high Young's modulus (as noted E). Although, the E is an intrinsic property of materials, which should be constant as the specimen size changes, but the E of small-sized specimens is reported to differ as the size changes. The E of a small-sized specimen with a specific geometry is called the effective Young’s modulus (E eff). The E eff of a micro-cantilever could be determined from the resonance frequency of the micro-cantilever, and the resonance frequency could be measured by a laser doppler vibrometer [4].In this report, various Ti/Au multi-layered structures, as shown in Fig. 2, were prepared. Firstly, the E eff of complex three dimensional (3D) multi-layered Ti/Au structures was determined from the resonance frequency obtained with a laser doppler vibrometer, as shown in Fig. 3. Next, we studied the effects of these various Ti/Au multi-layered structures on the long-term structure stability by vibration tests. Lastly, we discuss the relationship between the Ti/Au multi-layered structures with characteristic E eff values and long-term structure stability. The discussion could contribute to the material design for highly sensitive and stable MEMS accelerometers.Reference: Yamane, et al., Appl. Phys. Lett., 104, 074102 (2014).Onishi, et al., Jpn. J.Appl.Phys., 61, SD1028 (2022)Machida, et al., ECS Trans., 61, 21 (2014).Nitta, et al., J.Electrochem.Soc., 167, 082503 (2020)Teranishi et al., Microelectro. Eng. 187–188 , 105–109 (2018) Figure 1

Vibrations Analysis of Bubble Evolution in Liquids of Varying Physical Properties

In recent years there is an attempt to control the gas stirring intensity in metal-making ladles with the aid of vibration measurements. Understanding better the induced vibrations in two-phase flows can substantially improve the existing models for gas stirring control. In this work, highly sensitive accelerometers were used for the vibration measurements in a liquid metal alloy; Sn–40 wt pctBi alloy at 200 °C and water at 20 °C. The examination of the liquids was conducted in the ladle mockup integrated into the Liquid Metal Model for Steel Casting facility at Helmholtz-Zentrum Dresden Rossendorf. Single bubbles were generated in the respective liquids by controlled argon injection at low flow rates in the range of 0.01 to 0.15 NL min−1 through a single nozzle installed at the bottom of the ladle. Obtained results demonstrate differences between the induced vibrations in the examined liquids in terms of the magnitude of the root mean square values of vibration amplitude and the shape of the resulting curves with increasing flow rate. Furthermore, continuous wavelet transform reveals variations in the duration and vibrational frequency of the evolved bubble phenomena. The findings suggest that differences in the physical properties of the examined liquids result in variations in the vibrations induced during bubble evolution.

Equal-strength beam design of acoustic wave accelerometers

Abstract Surface acoustic wave (SAW) based accelerometers have received significant attention due to their digital output, low cost, mass production and easy implementation of wireless passive function. However, conventionally rectangular cantilever-beam based SAW accelerometers often have non-uniform strains generated along the beams, which cause emergence of parasitic wave modes and measurement errors. In this paper, a simulation platform was developed to analyze and optimize designs of SAW accelerometers and variable-thickness and equal-strength beams were designed to solve the critical issue of non-uniform strain distribution along the beam. Frequency responses of SAW accelerometers under the acceleration were successfully obtained using the simulation platform, with the visualized strain/stress distribution and particle displacement field. The accuracy of this simulation platform was verified using the experimental result reported in literature. A highly sensitive and equal-strength beam SAW accelerometer was achieved with a sensitivity up to 1.40 kHz g−1, a linearity coefficient of ∼1, and a measurement range of 0∼15 g. Furthermore, a high-G accelerometer was designed, with the capability of enduring large shocks up to 11,500 g and a sensitivity of 6.96 Hz g−1.

Diagnosis of Coexisting Valvular Heart Diseases Using Image-to-Sequence Translation of Contact Microphone Recordings.

Development of a contact microphone-driven screening framework for the diagnosis of coexisting valvular heart diseases (VHDs). A sensitive accelerometer contact microphone (ACM) is employed to capture heart-induced acoustic components on the chest wall. Inspired by the human auditory system, ACM recordings are initially transformed into Mel-frequency cepstral coefficients (MFCCs) and their first and second derivatives, resulting in 3-channel images. An image-to-sequence translation network based on the convolution-meets-transformer (CMT) architecture is then applied to each image to find local and global dependencies in images, and predict a 5-digit binary sequence, where each digit corresponds to the presence of a specific type of VHD. The performance of the proposed framework is evaluated on 58 VHD patients and 52 healthy individuals using a 10-fold leave-subject-out cross-validation (10-LSOCV) approach. Statistical analyses suggest an average sensitivity, specificity, accuracy, positive predictive value, and F1 score of 93.28%, 98.07%, 96.87%, 92.97%, and 92.4% respectively, for the detection of coexisting VHDs. Furthermore, areas under the curve (AUC) of 0.99 and 0.98 are respectively reported for the validation and test sets. The high performances achieved prove that local and global features of ACM recordings effectively characterize heart murmurs associated with valvular abnormalities. Limited access of primary care physicians to echocardiography machines has resulted in a low sensitivity of 44% when using a stethoscope for the identification of heart murmurs. The proposed framework provides accurate decision-making on the presence of VHDs, thus reducing the number of undetected VHD patients in primary care settings.

An Experimental Study of a Magnetic Liquid Marble and a Novel Scheme for Improving the Sensitivity of a Liquid Marble-Based Accelerometer

An Experimental Study of a Magnetic Liquid Marble and a Novel Scheme for Improving the Sensitivity of a Liquid Marble-Based Accelerometer

Identification of S2 Paradoxical Splitting in Aortic Stenosis Subjects via Seismocardiogram Signals From a Wearable Accelerometer Contact Microphone

Second heart sound (S2) splitting can be used as an indicator for diagnosis of cardiovascular diseases; specifically, paradoxical S2 splitting is an indicator of aortic stenosis. We present that S2 acoustic signatures can be captured accurately from the seismocardiogram (SCG) signals of a sensitive wearable accelerometer contact microphone (ACM) and validated by comparing with digital stethoscope phonocardiogram (PCG) signals. The ACM was placed on the pulmonic region of 18 subjects, 10 with no known heart disease and 8 with known heart disease, for 60 seconds of SCG data collection. Smoothed Pseudo Wigner-Ville distribution is used to extract S2 time split and to identify S2 paradoxical splitting. Healthy subjects had SCG S2 time splits range agreeing with S2 time splits from past literature from PCG signals. The ACM SCG signal was al-so used to identify and capture paradoxical splitting from subjects with known valvular heart diseases such as aortic stenosis, from subjects with mild to severe diagnosis. In conclusion, a wearable ACM can be used to detect paradoxical splitting in subjects suspected with aortic valvular heart disease and shows high fidelity of capturing S2 time split through SCG signals.

Amplitude–Frequency Noise Models for Seismic Building Monitoring in a Weak-to-Moderate Seismic Region

AbstractHerein, we discuss amplitude–frequency noise models for high-quality accelerometric monitoring of a civil engineering building and the benefits of seismic building monitoring policies in weak-to-moderate seismic regions. Since 2004, the city hall building in Grenoble (French Alps) has been monitored continuously. First, accelerometric data from one continuous year are used to derive broadband noise models for the bottom and top of the building. The noise models are compared with (1) the noise sensitivity of the high-gain accelerometer installed in the building and low-cost sensor sensitivity models; (2) the typical earthquake response curves given by Clinton and Heaton (2002); and (3) the earthquakes recorded in the Northern Alps. Then, using earthquakes data, this study highlights threshold values for signal-to-noise ratio (≥3 or 9 dB) recordings of earthquake as a function of magnitude and distance for weak-to-moderate earthquakes. We present a preliminary cost-benefit analysis of instrumentation for such regions according to seismic hazard and instrumentation quality. For weak-to-moderate seismic regions like Grenoble area, the capability of high-dynamic accelerometers to record low-amplitude ground motions and building responses is confirmed and encouraged to enable high-quality observation of building response over a broad range of frequencies. Bearing in mind that full-scale building test data are of greater interest for improving our understanding of building response than even the most sophisticated models, the recording of weak-to-moderate earthquakes in building must be broadened using high dynamic instruments to obtain more comprehensive and advanced results.

Calibration of high accuracy accelerometers for ESA missions BepiColombo and JUICE at INRIM

High sensitive triaxial accelerometers are used in several space missions to measure the non-gravitational accelerations acting on the spacecraft. Among these, the capacitive accelerometers developed for ESA missions Jupiter Icy moons Explorer (JUICE) and BepiColombo were designed to measure accelerations of the order of 3 · 10−6 m s−2 with an accuracy level of 300 ppm in the frequency range (3 · 10−5–0.1) Hz. Despite the signal to be measured is of the same order of magnitude of the seismic noise on the earth, an accurate on-ground calibration is needed. The facility set-up at INRIM to this purpose is based on a simple principle: the base of the accelerometer is dynamically tilted by an angle α so that the sensor undergoes a component of the gravitational acceleration g proportional to angle α. In practice, several issues have to be addressed by the calibration facility, such as the seismic noise limiting the signal-to-noise ratio, the generation and the accurate measurement of the tilt angle. Furthermore, the calibration was performed taking into account different on-flight conditions such as different operating temperatures and possible deformation of the accelerometers during the launch. The experimental set-up and the calibration procedure are described in the paper. The measurement results and the uncertainty budget show that a relative accuracy of 240 ppm has been achieved.

A Method for Synchronous Shock Calibration of Triaxial High-g Accelerometers Based on Modified Hopkinson Bar Technique

Since the width of the excitation pulse is generally in the order of microseconds to milliseconds, the key technique in the shock calibration of triaxial high-g accelerometer is how to achieve the synchronous loadings with high-g amplitude along the three orthogonal axes. Given this background, this paper developed a synchronous calibration method for the triaxial high-g accelerometers by modifying the conventional Hopkinson bar method. Using this newly developed method, three-dimensional reference acceleration pulses with amplitude range of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> g-10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> g and width range of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> μs-10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> μs can be generated and imposed on the triaxial high-g accelerometers synchronously. Then, calibration experiments on a typical triaxial high-g accelerometer were carried out by using both the synchronous calibration method and the conventional Hopkinson bar method, respectively. The sensitivity of the triaxial accelerometer was characterized by a matrix, the so-called sensitivity matrix, containing 3 main sensitivity coefficients and 6 transverse sensitivity coefficients. Least squares method (LSM) was used to calculate the sensitivity matrix. Generalization error was employed to evaluate the measurement accuracy of the accelerometer. The results show that the measurement accuracy of the triaxial high-g accelerometer calibrated by the synchronous method is higher than that calibrated by the conventional asynchronous method. Therefore, the developed synchronous method is recommended to ensure and improve the measurement accuracy of the triaxial high-g accelerometers. Finally, the validity and the calibration ability of the newly developed method were numerically investigated and discussed in detail.

A Double Differential Torsional Accelerometer With Higher Than 10-kHz Measurement Bandwidth for Vibration Monitoring

This paper reports the design, fabrication, ASIC, package, and characterization of a z-axis accelerometer with double differential torsional configuration. Compared with typical comb structures, diagonally large depth non-penetrating quad-mass has a simple structure with a large feature size. Compared with traditional unbalanced proof mass structures, the fully differential sensitive configuration theoretically eliminates the influence of common mode errors such as interference force and temperature variations. Thus a high performance structure with high sensitivity and good stability was obtained. Meanwhile, the anchor was arranged internally to make the structure more compact and less stress sensitive. The sensitive structure has a size of 2.4mm×1.8mm. An optimization of kinetic properties was done to get large bandwidth and small mechanical thermal noise. The ASIC of the double differential torsional structure was implemented, which adopted single-cycle clock double-edge multiplexing to improve C/V conversion efficiency and reduce circuit noise. At the same time, the error compensation technology used on the ASIC makes the accelerometer sensitivity error less than 1% and zero bias error less than ±0.02V. The resonance frequency is about 16kHz, the ±5% bandwidth is larger than 10kHz, the cross-axis sensitivities of the x-axis and y-axis are less than 1.5% and 1%, respectively, the bias instability is less than 700μg, the noise spectral density is better than 30μg/√ Hz above 10Hz, the normalized drift over the full temperature range (-40 °C to 60 °C ) is less than 1.78g under uncompensated conditions.

Primary microvibration standards down to 10−3 m s−2 at low frequency

The reliability of microvibration measurements is important in some applications, such as infrastructure health monitoring. Thus, it is necessary to develop a vibration standard based on ISO16063-11 for microvibrations. In this study, the low-frequency standard vibration calibration system in the National Metrology Institute of Japan was upgraded to be compatible with small input vibrations down to an amplitude of 10−3 m s−2. A low-noise reference vibration measurement system and a precise signal processing method were integrated to reduce the background noise contribution, which is a dominant uncertainty source in the field of microvibration calibration. The developed system could calibrate the sensitivity of a low-noise accelerometer down to 10−3 m s−2, between 0.1 Hz and 100 Hz. This paper reports the calibration demonstration using a servo accelerometer and the evaluated uncertainty budget. The estimated calibration uncertainty was 0.1% for a normal calibration process with an excitation of 10 m s−2, and it was 2.1% for a microvibration calibration process with an excitation of 10−3 m s−2.