Full-scale Range Research Articles

Experimental Validation of a Contactless Finger Displacement Measurement System Using Electrical Near-Field Sensing

This research investigates the potential of contactless finger motion measurement, focusing particularly on ease of use to improve the success of home-based hand rehabilitation exercises. Previously, a mathematical model was developed based on a finite-element method simulation. This article validates this model on multifinger noncontact measuring under laboratory conditions. Twenty-three healthy subjects with normal hand and finger functions participated. An independent near-field distance measurement was developed and compared with the output from an optical sensor. It was observed from the experiment that the prediction model worked well with the measuring system reported here. The average uncertainties of measurement using the prediction model are 0.68 and 0.55 mm, which are 3.5% and 2.7% of the full-scale range for the index finger and middle finger, respectively. The results from the experiment show that the reported system is capable of measuring the small movements of fingers. With the combination of the noncontact measuring feature and the lack of complicated setup, this system is easy-to-use as the basis of a home-based independent rehabilitation system.

Fiber-Optic Current Sensor Based on FBG and Terfenol-D With Magnetic Flux Concentration for Enhanced Sensitivity and Linearity

This paper presents the design, fabrication, and characterization of two compact fiber-optic current sensors (FOCS) based on fiber Bragg gratings (FBG) and the magnetostrictive alloy Terfenol-D. Finite-element-method (FEM) simulations assisted key optimizations in the geometry of similar FOCS proposed previously, allowing the implementation of magnetic flux density concentration techniques that resulted in sensors using very small amounts of Terfenol-D. Two prototypes of FOCS with the same geometry and size were manufactured for performance comparison purposes, one using a 2.21-g solid, bulk bar of Terfenol-D onto which a sensing FBG was bonded, and the other using magnetostrictive polymer composite (MPC) with oriented magnetic domains using only 0.42 g of Terfenol-D powder and epoxy resin with a sensing FBG embedded within the composite block. Both FOCS were characterized with currents of up to 800 Arms, and presented linearity errors smaller than 1% of full-scale range (FSR). The prototypes presented greater sensitivities taking into account that only less than 6% of Terfenol-D was employed in comparison to previous FBG-based FOCS. Transient-responses of the FOCS prototypes were also measured showing that the proposed sensors might be applied not only to current metering, but also to fault detection in high-voltage lines. Temperature compensation methods were also proposed and discussed for the developed FOCS.

Damping analysis of a quad beam MEMS piezoresistive accelerometer

ABSTRACT This article presents the simulation and experimental validation of damping for an MEMS (micro-electromechanical systems) piezoresistive accelerometer with an optimized mass dimension and air gap. A commercially available device should be able to withstand acceleration shock having a full-scale range of at least from 100 g to 1000 g irrespective of its nominal operation range. To achieve this, a micromachined silicon accelerometer is bonded with top and bottom Pyrex glasses. These glass plates provide viscous damping to the proof mass during its movement influencing the performance of the accelerometer. To improve the damping characteristics, the proposed accelerometer device is electroplated with gold on top of the device and an optimum distance of 27 µm is maintained between top/bottom glasses. It is observed that the vibrations are detected in a much earlier stage when the device is electroplated with gold with an optimum air gap distance of 27 µm. Experimental results prove an optimized air gap device for an electroplated gold with a proof thickness of 170 µm as a reduction of 23.26% from the resonant peak of electroplated gold device with a proof thickness of 270 µm. This device aims to design a typical air craft sensing motion application.

A Fully Differential and Power-Efficient Difference Integrating ADC

This paper proposes an energy-efficient fully differential difference integrating analog-to-digital converter (ADC) for image sensors and biomedical recording systems where the variation of the input analog signal is usually much smaller than the full-scale range of the signal. In order to find the digital code of the input analog sample, the proposed structure digitizes the voltage difference between the new analog sample and the previous one, leading to power saving. The proposed ADC not only improves the rounding problem existing in the previous structures, but also its sampling rate is doubled by employing two auxiliary comparators. Moreover, using a segmented architecture for the employed capacitive-array digital-to-analog converter reduces the capacitor switching activity and therefore the power consumption of the ADC. The proposed ADC is designed and simulated in TSMC 0.18-µm CMOS process. Post-layout simulation results of a 1-V, 8-bit, 40-kS/s ADC show that for low-varying input signals, the proposed circuit achieves a signal-to-noise-plus-distortion of 49.3 dB while consuming 220 nW power dissipation, leading to a figure of merit of 23 fJ/c-step. The silicon area occupied by the circuit is 300 µm × 215 µm.

Harmonic Distortion Optimization for Sigma-Delta Modulators Interface Circuit of TMR Sensors.

The tunneling magnetoresistance micro-sensors (TMR) developed by magnetic multilayer material has many advantages, such as high sensitivity, high frequency response, and good reliability. It is widely used in military and civil fields. This work presents a high-performance interface circuit for TMR sensors. Because of the nonlinearity of signal conversion between sensitive structure and interface circuit in feedback loop and forward path, large harmonic distortion occurs in output signal spectrum, which greatly leads to the reduction of SNDR (signal noise distortion rate). In this paper, we analyzed the main source of harmonic distortion in closed-loop detection circuit and establish an accurate harmonic distortion model in TMR micro-sensors system. Some factors are considered, including non-linear gain of operational amplifier unit, effective gain bandwidth, conversion speed, nonlinearity of analog transmission gate, and nonlinearity of polycrystalline capacitance in high-order sigma-delta system. We optimized the CMOS switch and first-stage integrator in the switched-capacitor circuit. The harmonic distortion parameter is optimally designed in the TMR sensors system, aiming at the mismatch of misalignment of front-end system, non-linearity of quantizer, non-linearity of capacitor, and non-linearity of analog switch. The digital output is attained by the interface circuit based on a low-noise front-end interface circuit and a third-order sigma-delta modulator. The digital interface circuit is implemented by 0.35μm CMOS (complementary metal oxide semiconductor) technology. The high-performance digital TMR sensors system is implemented by double chip integration and the active interface circuit area is about 3.2 × 2 mm. The TMR sensors system consumes 20 mW at a single 5 V supply voltage. The TMR sensors system can achieve a linearity of 0.3% at full scale range (±105 nT) and a resolution of 0.25 nT/Hz1/2(@1Hz).

12 b 50 MS/s 0.18 μm CMOS SAR ADC based on highly linear C‐R hybrid DAC

A 12 b 50 MS/s successive-approximation register (SAR) ADC with a highly linear C-R hybrid DAC is presented. The proposed DAC significantly reduces the required total number of unit capacitors by processing the upper bits based on a binary-weighted capacitor array and the remaining lower bits based on reference segment voltages, which are obtained from a simple resistor string. The reduced number of unit capacitors enables the use of larger unit capacitance, resulting in improved matching accuracy. In the C-R hybrid DAC, an input range scaling technique, which matches a full-scale input range to the reference voltage range, implements the binary-weighted SAR operation without additional capacitors and reference voltages. The DAC linearity is improved considerably through the process-insensitive capacitor-array layout, which cancels out oxide-gradient errors. The prototype ADC in a 0.18 μm CMOS process demonstrates measured differential and integral non-linearities within 0.71 LSB and 0.85 LSB at 12 b, respectively, with a maximum signal-to-noise-and-distortion ratio and a spurious-free dynamic range of 64.3 and 74.7 dB at 50 MS/s, respectively. The ADC occupies an active die area of 0.17 mm2 and consumes 2.63 mA with a 1.8 V supply voltage.

A Digital Closed-Loop Sense MEMS Disk Resonator Gyroscope Circuit Design Based on Integrated Analog Front-end.

A digital closed-loop system design of a microelectromechanical systems (MEMS) disk resonator gyroscope (DRG) is proposed in this paper. Vibration models with non-ideal factors are provided based on the structure characteristics and operation mode of the sensing element. The DRG operates in force balance mode with four control loops. A closed self-excited loop realizes stable vibration amplitude on the basis of peak detection technology and phase control loop. Force-to-rebalance technology is employed for the closed sense loop. A high-frequency carrier loaded on an anchor weakens the effect of parasitic capacitances coupling. The signal detected by the charge amplifier is demodulated and converted into a digital output for subsequent processing. Considering compatibility with digital circuits and output precision demands, a low passband sigma-delta (ΣΔ) analog-to-digital converter (ADC) is implemented with a 111.8dB signal-to-noise ratio (SNR). The analog front-end and digital closed self-excited loop is manufactured with a standard 0.35 µm complementary metal-oxide-semiconductor (CMOS) technology. The experimental results show a bias instability of 2.1 °/h and a nonlinearity of 0.035% over the ± 400° full-scale range.

Quarter-mm2 High Dynamic Range Silicon Capacitive Accelerometer With a 3D Process

A new 3D process is proposed for inertial MEMS sensors where a thin transduction layer based on high-density surface-varying comb fingers, with nano-metric gaps, is patterned below a thick seismic mass layer. The objective is to achieve high-performance in a reduced footprint. An in-plane accelerometer is designed, fabricated with this new 3D process, and tested under acceleration. Initial fabricated devices demonstrate a full-scale range of ±160 g, $7~\mu {g}/ \sqrt {\textit {Hz}}$ Brownian noise floor and more than 4 kHz bandwidth. These figures translate into a dynamic range of more than 150 dB (normalized to 1-Hz bandwidth) with an overall footprint of only ${400}\times {600}\,\,\mu {m}^{{2}}$ .

Built-in Harmonic Prediction Scheme for Embedded Segmented-Data-Converters

Increase in manufacturing test cost is of paramount issue to chip suppliers, which has been primarily due to costly external testers and long test-time. This paper proposes a loopback-based self-test technique to cost-effectively predict the dynamic nonlinearities of on-chip segmented digital-to-analog-converter (DAC) and analog-to-digital-converter (ADC), by externally looping a DAC back to an ADC, through an external load board employing two parallel paths: a programmable-gain-amplifier (PGA) path and a bypass path for test purpose. A segmented DAC (or ADC) consists of coarse and fine DACs (or ADCs). Two loopback tests are sequentially performed. For the first loopback test, a clean and single-tone sinusoidal signal is applied to a coarse DAC, and it bypasses a fine DAC for test purpose. The obtained DAC output is then fed to a coarse ADC through a bypass path on the load board. Simultaneously, the DAC output is applied to a fine ADC through a PGA path, so that the DAC output signal can fit into the input full-scale range of the fine ADC. For the second loopback test, a sinusoid is fed to a fine DAC, and it bypasses a coarse DAC in this time. Similarly, the DAC output is then applied to a fine and a coarse ADCs through two paths on the load board, at the same time. For postprocessing in on-chip processor, the correlation equations between the dynamic nonlinearities of sub-DACs/ADCs and the aforementioned loopback responses are simultaneously solved to predict the dynamic nonlinearity for each of a DAC and an ADC. Simulation and hardware measurements verified that the proposed technique can be practically used for production testing, by showing less than 0.28-dB and 0.55-dB of the prediction errors, respectively.

High-precision microdisplacement sensor based on zeroth-order diffraction using a single-layer optical grating.

A high-precision microdisplacement sensor based on zeroth-order diffraction of a single-layer optical grating is reported. Laser grating interference occurs when part of the laser is reflected diffraction by the grating and another part is vertically reflected back by a mirror and diffracted again by the grating, thus generating optical interferometric detection. For the purpose of obtaining the optimal contrast of the optical interferometric detection, the duty cycle of the grating and the orders of diffraction were optimized by the diffraction scalar theory. The microdisplacement sensor demonstrates a sensitivity of 0.40%/nm, a resolution of 0.6 nm, and a full-scale range of up to 100 µm. This work enables a high-performance displacement sensor, and provides a theoretical and technical basis for the design of a displacement sensor with an ultracompact structure.

A Tuning Fork Gyroscope with a Polygon-Shaped Vibration Beam.

In this paper, a tuning fork gyroscope with a polygon-shaped vibration beam is proposed. The vibration structure of the gyroscope consists of a polygon-shaped vibration beam, two supporting beams, and four vibration masts. The spindle azimuth of the vibration beam is critical for performance improvement. As the spindle azimuth increases, the proposed vibration structure generates more driving amplitude and reduces the initial capacitance gap, so as to improve the signal-to-noise ratio (SNR) of the gyroscope. However, after taking the driving amplitude and the driving voltage into consideration comprehensively, the optimized spindle azimuth of the vibration beam is designed in an appropriate range. Then, both wet etching and dry etching processes are applied to its manufacture. After that, the fabricated gyroscope is packaged in a vacuum ceramic tube after bonding. Combining automatic gain control and weak capacitance detection technology, the closed-loop control circuit of the drive mode is implemented, and high precision output circuit is achieved for the gyroscope. Finally, the proposed Micro Electro Mechanical Systems (MEMS) gyroscope system demonstrates a bias instability of 0.589°/h, an angular random walk (ARW) of 0.038°/√h, and a bandwidth of greater than 100 Hz in a full scale range of ± 200°/s at room temperature.

Notice of Violation of IEEE Publication Principles: A Miniaturized Five-Axis Isotropic Tactile Sensor for Robotic Manipulation

Notice of Violation of IEEE Publication Principles Five-Axis Isotropic Sensor for Robotic Manipulation by Zhongyi Chu, Lin Su, Gen Chen, Jing Cui, and Fuchun Sun in IEEE Sensors Journal, Vol. 19, No. 22, Nov 2019 After careful and considered review of the content and authorship of this paper by a duly constituted expert committee, this paper has been found to be in violation of IEEE’s Publication Principles. This paper contains portions of text from the paper(s) cited below. A credit notice is used, but due to the absence of quotation marks or offset text, copied material is not clearly referenced or specifically identified. Tactile Sensing for Gecko-Inspired Adhesion by X. Alice Wu, Srinivasan A. Suresh, Hao Jiang, John V. Ulmen, Elliot W. Hawkes, David L. Christensen and Mark R. Cutkosky in the Proceedings of the 2015 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) Miniaturized multi-axis (force & torque) tactile sensors are paramount for the robot system to interact safely with the external environment, especially for the controlled adhesive robots. However, there exists a drawback--measurement anisotropy, which prevents sensors from performing equally well in all the directions and the high degree of integration. Based on the plate capacitive mechanism, this paper introduces a miniaturized 5-axis tactile sensing method with a novel doublelayer sensitive structure. Practically, shear force is detected by measuring the change of overlap area in the upper-layer-sensing cell, while the normal force and moment can be obtained by the variable space between two plates arranged in a 2 × 2-grid in the lower-layer-sensing cell. Moreover, in order to achieve the measurement isotropy, the relationship between the force/torque and the capacitance is clarified to facilitate the independent adjustment of the sensitivity of each axis. Based on the methodology, a miniature 5-axis flat tactile sensor is manufactured. The experimental results show that the shear sensitivity of the prepared sensor is over 0.2557pF/N within 7 N, reaching the same magnitude as normal force (0.2859pF/N over 3N range). The sensitivities of torque are over 1.8406 (N · m) -1 with a full-scale range of 0.04 N·m. The results demonstrate that the miniaturized tactile sensor is capable of isotropic measurement among 5-axis for robotic manipulation.

A General Purpose 1.8-V 12-b 4-MS/s Fully Differential SAR ADC With 7.2-Vpp Input Range in 28-nm FDSOI

This brief describes a differential, 1.8-V, 12-bit 4-MS/s successive approximation register (SAR) analog to digital converter (ADC) with innovative input switch that supports up to 3.6 V inputs using only 1.8-V devices in 28-nm process. This SAR ADC is based on 6–6 split capacitor digital to analog converter architecture with separate sampling capacitor. It features eight pairs of differential input channels. It has a full-scale input range, multiple speed/power modes, and power-down mode for low current consumption. The ADC performs to 11.35 effective number of bits when tested up to 125 C at supply voltages ranging from 1.6 V to 2.0 V and reference voltages ranging from 0.8 V to 2.0 V. Fabricated in a 28-nm fully depleted silicon on insulator process with fringe capacitors, it occupies an area of 0.13 mm2 and has a total dissipation of 960 $ {\mu }\text{A}$ in full speed differential mode and 400 ${\mu }\text{A}$ in low-power single-ended mode. The ADC has been integrated and is in production.

Conceptual Design of a Resonant Pirani Gauge Toward Wide-Range Pressure Sensing

This letter reports a CMOS-microelectromechanical system (MEMS) pressure sensor comprising a double-ended tuning fork capacitive resonant transducer and a Pirani gauge thermal transducer in a single device configuration, which demonstrates a wide-range pressure sensing capability, small form factor, and sensor fusion. The device integrated with an interfaced circuit was fabricated through a 0.35- μ m CMOS foundry process, together with an in-house release process. Thanks to the resonant transducer which is sensitive to pressure due to squeezed-film damping effect, the high pressure sensing range is achieved by measuring resonant frequency shift, whereas the medium pressure region is sensed by quality factor ( Q ) change of the resonator. As a result, a full-scale range of 10–760 torr is realized by the proposed CMOS-MEMS pressure sensor using its resonant transducer. To further extend the measurement range to the lower pressure range, an embedded thermal transducer of the device is used to serve as Pirani gauge that is capable of detecting pressure from 0.02 to 10 torr by the use of thermal resistance $(R_{{\rm{th}}})$ change. Through a simple algorithm combining variations of Q , resonant frequency $f_{o}$ , and thermal resistance $R_{{\rm{th}}}$ , the proposed resonant Pirani gauge pressure sensor features a very wide-range pressure sensing capability from 0.02 to 760 torr.

Optical high-voltage sensor based on fiber Bragg gratings and stacked piezoelectric actuators for a.c. measurements.

In this paper, we present the design and fabrication of a compact, modular optical high-voltage sensor (OHVS) based on fiber Bragg gratings (FBG) for a.c. distribution and transmission lines. The proposed OHVS is composed by a stack of piezoelectric transducers that transfer mechanical strain to a sensing FBG. A prototype was tested in the laboratory and showed a maximum linearity error of less than 3% of full-scale range (FSR) for input voltages up to ${14\,\,{\rm kV}_{\rm rms}}$14kVrms with a signal-to-noise ratio of 55 dB, allowing measurements with a resolution of less than 0.2% of FSR. Transient response of the developed OHVS was preliminarily investigated, and a response time of less than 1 ms was observed. The results obtained allow us to conclude that the developed OHVS may also be used for the detection of transient events.

CMOS time-mode smart temperature sensor using programmable temperature compensation devices and $$\Delta \Sigma$$ time-to-digital converter

This work presents a time-mode smart temperature sensor in a standard 180 nm CMOS process, intended for on-chip thermal monitoring applications. A new temperature-to-pulse converter (TPC) is proposed utilising programmable temperature compensation devices, where a dual delay-line configuration is adopted, namely sensor and reference delay-lines. The proportional to absolute temperature (PTAT) delay offered by the sensor delay-line has a temperature coefficient (TC) of 720 ppm/°C, whereas almost constant delay possessed by the reference delay-line has a TC of 60 ppm/°C, over 0–100 °C temperature range. The proposed 1st-order $$\Delta \Sigma$$ time-to-digital converter (TDC) serves as the smart sensor readout, where a novel delay-cell is proposed using multipath approach. The projected $$\Delta \Sigma$$ TDC achieves 30 ns full-scale range at 9 ps resolution. The dual delay-line configuration in the TPC and the dynamic element matching in the $$\Delta \Sigma$$ TDC bound the inaccuracy of the proposed smart temperature sensor to ± 0.68 °C. The sensor shows a resolution of 0.03 °C at 0.5 $$\upmu \hbox {s}$$ conversion time.

Design and fabrication of SOI technology based MEMS differential capacitive accelerometer structure

This paper discusses the design and fabrication of MEMS differential capacitive accelerometer (z-axis sensitive) structure. The accelerometer structure consists of one each movable and reference capacitors in the single accelerometer die fabricated using highly conductive (p-type, resistivity: 0.001 Ω cm) SOI substrate. Resonant frequencies of the designed movable and reference capacitive structures were found to be 9.6 kHz and 150 kHz respectively. Corresponding rest capacitance (at 0 g) of both the capacitors was 2.21 pF. The movable and reference structures showed a deflection of 0.14 µm and 0.6 nm respectively at 50 g applied acceleration. Corresponding changes in capacitances of the movable and reference capacitors were 82.3 fF and < 0.33 fF respectively. The designed accelerometer showed a scale factor sensitivity of the movable capacitor was of ~ 1.65 fF/g. The device demonstrated a dynamic range of in − 17 g to 42 g with a full-scale non-linearity of ~ 3%. Corresponding measured scale factor sensitivity in the centrifuge test was found to be ~ 47 mV/g with an acceleration resolution of ~ 17 mg. The device exhibited cross-axis sensitivity of ~ 2% in the full-scale range. Measured 3 dB bandwidth (380 Hz) of the device matches reasonably with the simulated value (~ 400 Hz).

Characterization of SOI technology based MEMS differential capacitive accelerometer and its estimation of resolution by near vertical tilt angle measurements

This paper discusses the evaluation and testing of MEMS capacitive accelerometer (z-axis sensitive) fabricated using silicon-on-insulator (SOI) wafer. The accelerometer structure consists of highly conductive (p-type, resistivity: 0.001 Ω-cm) silicon proof mass (1000 μm × 1000 μm × 30 μm) suspended by four crab-like L-shaped beams (1150 μm × 30 μm × 30 μm) over Pyrex (7740) glass cavity (5 μm depth). Rest capacitance of the accelerometer structure is found to be ~ 2.1–2.25 pF range. Qualified accelerometer chips are packaged and sealed in lead less ceramic (LCC) package along with capacitive readout circuitry chip. Packaged accelerometer showed a scale factor sensitivity of ~ 47 mV/g in − 17–42 g acceleration range with 3% non-linearity. Corresponding cross-axis sensitivity also measured (2%) in full-scale range. Frequency response of the accelerometer showed a 3 dB bandwidth of 380 Hz. Resolution of the accelerometer is measured by an innovative technique involving inclinometer. Here, the device output is recorded at near vertical mounting tilt angle (θ ~ 90°) of inclinometer. Present accelerometer output can be resolved at the inclinometer measurement at 90° (output: 2.42662 V) and 89° (output: 2.42780 V) which corresponds to an acceleration resolution of ~ 17 mg.

Elasticity Measurement of Soft Tissues Using Hybrid Tactile and MARG-Based Displacement Sensor Systems

This paper presents a novel soft tissue elasticity measurement technique based on the fusion of Magnetic, Angular Rate, and Gravity (MARG) sensors and fixed tactile sensors. This paper is intended both as a stand-alone technology and as an extension of traditional tactile imaging of the breast to allow for accurate diagnosis of breast lesions. A series of artificial silicone materials known to imitate soft biological breast tissues is characterized using the proposed system and compared against an Instron universal testing machine to determine the system accuracy and repeatability. Comparing the characteristics of ten distinct materials, with elasticities in the range 9-90 kPa, determined by the proposed system to those from the Instron yields accuracy within 4% over the full-scale range. Interexperimental repeatability is within 1.5%. The proposed system delivers absolute elasticity of materials to within 4%, which, when combined with its lack of moving parts and low implementation cost, can significantly improve the diagnostic capability of tactile imaging in the clinical environment. By applying this technique, to determine the background elasticity of breast tissue, in conjunction with the relative lesion elasticity result from tactile arrays, the full non-invasive diagnostic potential of tactile imaging can be realized with the effect of reducing benign biopsy rates, secondary care costs, and patient stress.

A Low-Cost Time-Correlated Single Photon Counting Portable DNA Analyzer.

Photon-counting analysis of nucleic acids plays a key role in many diagnostics applications for its accurate and non-invasive nature. However, conventional photon-counting instrumentations are bulky and expensive due to the use of conventional optics and a lack of optimization of electronics. In this paper, we present a portable, low-cost time-correlated single photon-counting (TCSPC) analysis system for DNA detection. Both optical and electronic subsystems are carefully designed to provide effective emission filtering and size reduction, delivering good DNA detection and fluorescence lifetime extraction performance. DNA detection has been verified by fluorescence lifetime measurements of a V-carbazole conjugated fluorophore lifetime bioassay. The time-to-digital module of the proposed TCSPC system achieves a full width at half maximum (FWHM) timing resolution from 121 to 145 ps and a differential non-linearity (DNL) between −8.5% and +9.7% of the least significant bit (LSB) within the 500 ns full-scale range (FSR). With a detection limit of 6.25 nM and a dynamic range of 6.8 ns, the proposed TCSPC system demonstrates the enabling technology for rapid, point-of-care DNA diagnostics.