Large Measurement Range Research Articles

Development of a force measurement system with a large punctual measurement range

Atomic force microscopes (AFMs) are precise force measurement instruments that can be used to measure multiple surface properties, such as adhesion force, surface potential, and elasticity at the nanoscale. AFM is increasingly used in diverse fields, especially in industrial applications. However, most existing commercial AFMs provide a scanning range of less than a few 100 μm. Moreover, the size of the sample must usually be less than a few centimeters to fit the mechanical constraints of the device. In this paper, we propose a gantry-type force measurement system that can perform force curve measurements over a large range. The measurement range of the proposed device is 240 mm minus the sample width in air environments. In liquid environments, the measurement range is mainly limited by the size of the Petri dish. For instance, a measurement range of 41.5 mm can be achieved by using a Petri dish having a diameter of 85.5 mm. In the experiments, (a) surface adhesion measurements on the ultraviolet/ozone (UV/O3) treated glass slides in air and (b) surface potential measurements on a mica surface in water were performed. The experimental results were consistent with the values obtained by the commercial AFMs, which demonstrated the accuracy of the proposed system.

Flexible three-dimensional force sensor of high sensing stability with bonding and supporting composite structure for smart devices

Characteristics, such as large measurement range, good repeatability and stability, are the guarantee for a wide application of flexible three-dimensional force sensors in robots and other smart devices. In this research, a flexible three-dimensional force sensor is presented, whose structure includes force-sensitive cells, fixed under the bump and a support layer, filled around the force-sensitive cells. This setup allows the sensor to quickly recover, after the force is released, to ensure its excellent performance. The production method is very simple and has the advantage of large-scale and low-cost manufacturing. The sensor exhibited good repeatability and stability, after 25 000 cycles of loading and releasing, under 8 N force. Meanwhile, it has a large measuring range, which is 0–15 N in the direction of normal force and 0–5.5 N in the direction of shear force. The sensitivity of the sensor in the x, y, and z directions is 1.5321 V−1 N−1, 1.501 29 V−1 N−1, and 0.936 87 V−1 N−1, respectively. The load response time of the sensor is 33 ms and the unload recovery time of 18 ms. Regarding practical applications, the sensor shows good prospects. For example, the sensor and its array can be installed on the manipulator to sense the magnitude and location of the three-dimensional force; in the case of the flexible smart keyboard, the presented sensor array can save space significantly and recognize multiple specific input features, in order to enhance information security; while as a car controller, it is multi-functional integrated and portable, thus showing great potential as replacement to the traditional operating methods.

A High-Precision and Wideband Fundamental Frequency Measurement Method for Synchronous Sampling Used in the Power Analyzer

In the dedicated high-precision power quality analyzer, synchronous sampling is required to reduce the effect of spectrum leakage produced by the discrete Fourier transform process. Thus, accurate fundamental frequency measurement is urgently needed. However, due to the harmonics and noise in the power signal, it is difficult to achieve the accurate fundamental frequency measurement. Moreover, with the wide application of high-frequency programmable power supply, the fundamental frequency is gradually increasing, which requires power analyzers to have the abilities of both high precision and a wide range of the fundamental frequency measurement. To solve these issues, a new fundamental frequency measurement architecture used in synchronous sampling is proposed. This architecture consists of a small-point fast Fourier transform module, spectrum refinement algorithm, and a multimodal optimization method to calculate the accurate fundamental frequency under large harmonic conditions. In the practical hardware platform results, this architecture has a large fundamental frequency measurement range from 20 Hz to 200 kHz with a relative error which is <0.004%. The wideband fundamental frequency measurement structure proposed in this article achieves high measurement accuracy.

Three-degree-of-freedom autocollimator with large angle-measurement range

Autocollimators (ACs) are primarily used for two-dimension measurement with small angle. A three-dimensional AC (3D-AC) with a large measurement range and capable of 3D angle measurement is proposed based on a modified cube corner reflector (MCCR). The MCCR structure is designed by establishing the space coordinate vector relation model between AC and the reflectors with the rotation relation of Euler space. A 3D-AC angle measurement equation for MCCR dimension angle recognition is established. Experiments demonstrate that the proposed 3D-AC model can be used for 3D measurement. The measurement range of 3D-AC is 10°, and the uncertainty values for the one-dimensional and combined angle measurements are (57.10″, 55.25″, 40.43″) and (394.16″, 455.36″, 319.57″), respectively.

A probe-type high-precision micro-force sensor based on quartz DETF resonator

Force measurement is widely applied in many applications. Resonant force sensors are featured with high accuracies, high resolutions, and long-term stabilities. In this paper, we report a probe-type high-precision force sensor based on a quartz resonator. The scale factor of our sensor is 161.5 mHz μN−1 and the bias stability of the sensor is 20 ppb (parts per billion) for an averaging time of 0.2 s. A comprehensive test showed that the nominal theoretical resolution of our sensor was 5 nN, and the repeated stability of our sensor has been proven by several controlled tests. With its large measurement range of 50 mN, the dynamic range of the sensor is up to 140 dB.

Defocused projection model for phase-shifting profilometry with a large depth range.

Phase-shifting 3D profilometry is widely combined with defocused projection, but the accuracy of defocused projection could be far below expectations especially in the case of large depth range measurement. In this paper, a new defocus-induced error related to the shape of the measured object is pinpointed and a novel defocused projection model is established to cope with such a error to improve the accuracy of defocusing phase-shifting profilometry. Supplemented with a specialized calibration and reconstruction procedure, the phase is well corrected to obtain accurate measurement results. Furthermore, the impact of the defocus-induced error is analyzed through simulations, and the feasibility of our method is verified by experiments. Faced with issues involving a large measurement range, the proposed method is expected to give a competitive performance.

Grating double-slot micro-ring resonator for sensing

A compact grating double-slot micro-ring resonator (GDSMRR) based on an SOI platform with a footprint of less than 11 μm ×11μm is analyzed and proposed in order to achieve a refractive index sensor with high sensitivity (S) and large measurement range. And EIT-like effects of high Q factor are achieved by combining structure of the double-slot micro-ring and Bragg grating. In the absence of a free spectral range (FSR) limitation, the measurement range of the sensor is significantly improved. In the refractive index sensing applications, Q value is 4325, S value is 433.33 nm/RIU, and DL 8.26 × 10−4 RIU. Thus, the proposed compact GDSMRR with excellent performance has great value for exploration in sensing applications.

An optical contact force sensor for tactile sensing based on specklegram detection from concatenated multimode fibers

An optical contact force sensor based on specklegram detection was proposed and validated for tactile sensing in this research. The specklegrams from different multimode fiber (MMF) based structures were firstly analyzed and compared in detail. Two of the structures based on the concatenation of MMF and few mode fiber (FMF) were selected. In the experiment, only the section of MMF is housed in a specially designed sensor head by 3D printing and the FMF section is used to lead the light out to the camera. The concatenated fiber structure enables the sensitive response to the applied force and shows insensitivity to the disturbance along the light lead-out part. With a contact force applying to the sensor head, bending of the MMF could be induced, which results in a deformed specklegram. In this way, the zero-mean normalized cross-correlation coefficient of the fiber specklegrams goes down with the increase of the contact force. For the selected fiber structure with different parameters, different sensitivity and different measurement ranges of force are realized, of which the largest linear measurement range of force is 0–23 N. Compared with only adopting MMF, the proposed scheme presents better stability together with a large measurement range and the flexibly adjusted sensitivity by changing the parameters of the fiber or the sensor head.

Single-shot digital multiplexed holography for the measurement of deep shapes.

This work develops a single-shot holographic profilometer that enables shape characterization of discontinuous deep surfaces. This is achieved by combining hologram frequency multiplexing and an illumination technique of complex amplitude in multi-incidence angle profilometer. Object illumination is carried out from seven directions simultaneously, where the radial angular coordinates of illumination plane waves obey the geometric series. It is shown that: (i) the illumination pattern provides the required frequency separation of all object wavefronts in transverse frequency space, which is necessary for hologram demultiplexing, and (ii) numerical generation of longitudinal scanning function (LSF) is possible, which has large measurement range, high axial resolution, and small side lobes. Low side lobes of LSF and the developed multiplexed field dependent aberration compensation method are essential to minimize the negative influence of speckle noise of single-shot capture on the measurement result. The utility of the proposed method is demonstrated with experimental measurement of heights of two step-like objects.

Standing wave drift of hemispherical resonator with quality factor non-uniformity under a ring electrode excitation

Hemispherical Resonator Gyroscope (HRG) is a classical high precision Coriolis Vibration Gyroscope (CVG), which performs attitude estimation of carrier by detecting the precession of standing wave of resonator, thus, the drift of standing wave of resonator has a great influence on the output accuracy of gyroscope, where the quality factor non-uniformity of resonator is one of main error sources. Ring electrode is a classical excitation structure of HRG because the standing wave can precess freely under its excitation, which makes the gyroscope have more accurate scale factor, larger measurement range and better dynamic characteristics. In this paper, the equations of motion of an ideal resonator excited by a ring electrode are derived by the elastic thin shell theory and Lagrange mechanical principle, then the corresponding equivalent mechanical model is established. According to the “average method”, it can be seen that the ideal resonator excited by the ring electrode works in integral mode, and any position in the circumferential direction of resonator can be a working point, which means that the quality factor non-uniformity has a great effect on the drift of standing wave. Therefore, the equations of motion of resonator with quality factor non-uniformity under the ring electrode excitation are deduced by the equivalent mechanical model, and the drift model of standing wave is established by the “average method”, it can be found that both the amplitude of quality factor non-uniformity and angle between the “inherent damping axis” and antinode axis of standing wave can affect the drift rate of standing wave. Moreover, the drift model indicates that if the input angular rate does not reach the threshold, the precession angular rate of standing wave will appear “self-locking” phenomenon, that is, the gyroscope will lose the integral effect.

Improved Pound-Drever-Hall Techniques for High Resolution Optical Fiber Grating Sensors

The interrogation technology plays a key role in high resolution fiber grating sensors. Due to the high sensitivity and quick response, the Pound-Drever-Hall (PDH) technique is one of the most successful interrogation methods in the high resolution fiber grating sensor systems. However, the traditional PDH technique can only interrogate one sensing element with limited measurement range, and can’t fully exploit the capability of optical fiber sensors. To break through this limitation, lots of efforts have been put to improve the PDH technique. This article reviews the recent improvements on PDH technique towards large measurement range and low probe power interrogation. Sideband interrogation method and high order PDH technique are proposed to expand the measurement range without tuning the laser frequency; In order to enable low probe power interrogation, which is essential in multiplexed sensing, coherent PDH and active PDH techniques are developed. Those improvements will promote the further development of PDH technique and provide powerful tools for high-resolution sensing applications.

PM Level and Large Dynamic Range Glucose Detection Based on a Sandwich Type Plasmonic Fiber Sensor

A sandwich type titled fiber Bragg grating (TFBG) plasmonic sensor based on self-assembled p-mercaptophenylboronic acid (PMBA) monolayer and Au nanoparticles (AuNPs), has been demonstrated and successfully applied for sensitive and stable low-concentration glucose detection. The sensor was immobilized with PMBA monolayer acting as the highly sensitive and stable glucose recognition molecule instead of a traditional unstable enzyme. In the experiments, the high sensitivity for glucose detection is achieved, establishing a competitive limit of detection (LOD) of 295 pM and large dynamic measurement range from 1 nM to 10 mM simultaneously. Moreover, due to the unique two-set diol configurations of glucose, the combination of TFBG-SPR with AuNPs and PMBA exhibit a good selectivity over fructose and galactose, which both possess only one set of diol configurations. Non-invasive saliva glucose detection, as a better alternative to blood, has emerged and attracted many researchers' attention. Therefore, the practicality of this method was successfully validated by detecting glucose in a simulated human saliva sample. We believe that this method represents an appealing solution for flexible, temperature-insensitive, high-sensitivity, and high-stability detection of ultra-low concentration glucose in modern non-invasive point-of-care testing as well as tumor micro-environment (TME) related cancer research.

Fast structured illumination microscopy with a large dynamic measurement range.

Fast structured illumination microscopy plays an important role in micro-nano detection due to the features of high accuracy, high efficiency, and excellent adaptability. The existing method utilizes the linear region of the axial modulation response curve (AMR), and by building the relationship between the modulation and the real height, achieves topography recovery. However, the traditional method is limited to narrow dynamic measurement range due to the linear region of the AMR being very short. In this paper, a double-differential fast structured illumination microscopy (DDFSIM) is proposed. By introducing two additional detectable branches for building the double-differential axial modulation response curve (DDAMR), the proposed method can obtain a large dynamic measurement range. In the measurement, three charge-coupled devices are respectively placed in and behind and before the focal plane to generate three axial modulation response curves. Three AMRs are used to set up the DDAMR, which has a large dynamic measurement range. Through simulation and experimental verification, the measurement range of DDFSIM is twice that of the conventional method under the same system parameters.

High-sensitivity and large-range fiber optic temperature sensor based on PDMS-coated Mach-Zehnder interferometer combined with FBG.

Although numerous efforts have been dedicated towards developing fiber sensors with high performances, challenges still remain in achieving high-quality temperature sensors with high sensitivity, large measurement range and high stability. This study proposes a compact fiber optic temperature sensor based on PDMS-coated Mach-Zehnder interferometer (MZI) combined with FBG, and it can realize both high-sensitivity and large-range temperature measurement. The MZI is based on Thin No-Core Fiber (TNCF) with lateral-offset. Owing to the high refractive index sensitivity of MZI and the high thermo-optic coefficient of PDMS, the sensor can achieve a high temperature sensitivity (>10 nm/°C). Besides, by optimizing the TNCF length, the cascaded FBG can be used to locate different temperature intervals in units of approximately 10 °C, and therefore the detectable temperature range is largely extended. The experimental test demonstrates that the average sensitivities of 11.19 nm/°C, 8.53 nm/°C, 7.76 nm/°C, 7.27 nm/°C are achieved at the temperature around 30 °C, 40 °C, 50 °C and 60 °C, and it shows excellent consistency and repeatability during the thermal cycle tests.

Differentiation of Multiple Mechanical Stimuli by a Flexible Sensor Using a Dual-Interdigital-Electrode Layout for Bodily Kinesthetic Identification

Human bodily kinesthetic sensing is generally complicated and ever-changing due to the diversity of body deformation as well as the complexity of mechanical stimulus, which is different from the unidirectional mechanical motion. So, there exists a huge challenge for current flexible sensors to accurately differentiate and identify what kind of external mechanical stimulus is exerted via analyzing digital signals. Here, we report a flexible dual-interdigital-electrode sensor (FDES) that consists of two interdigital electrodes and a highly pressure-sensitive porous conductive sponge. The FDES can precisely identify multiple mechanical stimuli, e.g., pressing, positive bending, negative bending, X-direction stretching, and Y-direction stretching, and convert them into corresponding current variation signals. Moreover, the FDES exhibits other exceptional properties, such as high sensitivity, stretchability, large measurement range, and outstanding stability, accompanied by simple structural design and low-cost processing simultaneously. Additionally, our FDES successfully identifies various complex activities of the human body, which lays a foundation for the further development of multimode flexible sensors.

A flexible metal thin film strain sensor with micro/nano structure for large deformation and high sensitivity strain measurement

Flexible strain sensors have been garnering substantial attention since being proven to be an effective means to acquire critical biomarkers for monitoring the states of the movement of organisms. This work introduces a flexible metal thin film strain sensor with micro/nano structure which has large measurement range and high sensitivity strain measurement. The large measurement range can be realized by the bugles that avoiding expanding of cracks and the high sensitivity is attributed to the disconnection-reconnection process by nanoscale cracks. In experiments, a flexible strain sensor with 30 nm Au nano-film was researched, and the results show that the maximum strain measurement range of the Au nano-film flexible sensor with micro/nano bulge structure can reach to 80%, and the gauge factor (GF) can reach to 20. In addition, the good repeatability and stability were proved by more than 1000 times cycles. Finally, this flexible sensor was attached to human’s fingers for real-time monitoring of the state of human joints and was demonstrated to have good comprehensive performance and usability. These features create opportunities for applying in many fields like wearable medical devices, e-skin, flexible robots and so on.

High sensitivity and large measurable range distributed acoustic sensing with Rayleigh-enhanced fiber.

In this Letter, high sensitivity and large measurable range distributed acoustic sensing (DAS) based on sub-chirped-pulse extraction algorithm (SPEA) in time domain and dechirp operation is proposed; moreover, Rayleigh-enhanced fiber is used to further improve the quality of Rayleigh scattering (RS) signal. In the proof-of-concept experiment, the RS pattern with 60 µɛ strain range is generated during a single-shot measurement, while $80.7 \; {\rm p}\varepsilon /\sqrt {\rm Hz}$ strain sensitivity and 28.4 cm spatial resolution are achieved on 920 m fiber.

High-accuracy deflectometric microscope system with a large slope range.

We propose an off-axis deflectometric microscope system for microscopic surface testing with both high measurement accuracy and a large slope dynamic range. A high-luminance liquid crystal display directly illuminates the tested sample with coded fringes, and then the reflected fringes passing through a microscope objective are captured by a pinhole camera, from which the deflectometric microscopic testing with a large slope range can be achieved. The accuracy of the proposed system is validated numerically and experimentally, and a large measurable slope dynamic range is also demonstrated. The proposed system provides a feasible way with the slope range in the order of sub-radians and sag resolution better than 0.05 nm.

Evaluation of a new automated immunoassay for the quantification of anti-Müllerian hormone

ObjectivesA newly developed fully automated Lumipulse G AMH method (Fujirebio Diagnostics) was recently introduced in clinical laboratories for quantitative determination of anti-Müllerian hormone (AMH) level in human serum or plasma. AMH has emerged as value-added biomarker in the assessment of ovarian reserve, in diagnosis of granulosa cells cancer and in the investigation of gonadal disorders. We compared Lumipulse G AMH assay performances with other methods largely applied for AMH measurements. Design and MethodsThe Lumipulse G AMH method based on two-step sandwich chemiluminescence enzyme immunoassay was assessed on Lumipulse G600II analyzer. The evaluation study included imprecisions, sensitivity and linearity whereas a comparison study was performed on a heterogeneous population of 114 patients by using the Elecsys AMH Plus assay on COBAS 8000 e602 module (Roche Diagnostics). ResultsLumipulse G AMH system showed good repeatability (within-run imprecision) with CV values below 1% (0.5% and 0.9% for high and low serum pools). Similarly within-laboratory imprecision was assessed with CV values of 2.5% and 1.6% for high and low level controls respectively. A linearity regression formula of 1.0119x-0.067 with a coefficient of determination (r2) equal to 0.999 was obtained in a range from 0.044 to 22.42 ​ng/ml. Passing-Bablok regression analysis was performed for assay comparability of AMH measurements. Results were closely correlated (correlation coefficient ​= ​0.997) with a regression equation (y ​= ​1.230x-0.025) showing a positive slope. Also, Bland-Altman analysis confirmed a good agreement between Lumipulse G AMH and Roche Elecsys AMH Plus assays with a bias of 17.76% in a large measurement range. ConclusionsThe performance of Lumipulse G AMH system was highly comparable with that of Roche Elecsys AMH Plus assay although approximately 10% higher values of AMH levels were observed for Lumipulse AMH system at all range of concentrations. Nevertheless the Lumipulse G system seems to be largely suitable for quantitative determination of AMH level in small-scale laboratory because of the reduced size and the use of single cartridge per test assuring flexibility and easy handling.

High resolution and large sensing range liquid level measurement using phase-sensitive optic distributed sensor.

Liquid level sensor with large sensing range and high-resolution is essential for the application of industry monitoring. In this work, a distributed optical fiber liquid level sensor is proposed and demonstrated based on phase-sensitive optical time domain reflectometry (φ-OTDR). In the basic of the thermal optic effect, the temperature change will induce the fluctuation of the effective refractive indexes of the fiber core, as well as the fluctuation of the optical path of the light transmitting in the fiber. Therefore, the φ-OTDR can detect the liquid level with a large measurement range by interrogating the phase information along the fiber due to the temperature difference between the liquid and air. Further, the scattering enhanced optical fiber (SEOF) is used as the sensing fiber to improve the signal to noise ratio (SNR) of the phase signal. Moreover, a high sensitivity liquid level sensing head by wrapping the SEOF on a heat conductive cylinder is designed and optimized to improve the sensing resolution. In the experiment, the proposed distributed liquid level sensor presents a high sensitivity of 73.4 rad/mm, corresponding to a competitive liquid level resolution of 142μm based on the noise floor of 10.4 rad within 160 s. The field test validates a large sensing range of 20 cm which is limited by the cylinder length, while a potential sensing range could reach 320 m with the sensing fiber of 40 km, proving a dynamic range of 127.1 dB. The proposed liquid level sensor with large dynamic range and high sensing resolution can benefit potential application in smart industry platforms and biomedicine monitoring.