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Accurate volume measurement of flying droplets in the Mura-free manufacturing of inkjet printed organic light-emitting diodes (IJP OLEDs) remains a challenge due to the micrometer scale and high speeds of the droplets. Most existing vision-based methods pay little attention to image segmentation and estimate the droplet volume based on a symmetry assumption, which yields poor accuracy, especially for droplets with an unknown shape. In this paper, an accurate measurement method for flying droplet volume based on stereo vision is proposed. First, an image acquisition technique based on stereo vision and synchronous triggering is used to obtain multiview high-resolution droplet images. Then, an accurate binocular droplet image segmentation algorithm is proposed to segment the images with different degrees of blur to achieve similar accuracy. Finally, a polar-coordinate-Hermite-interpolation-based droplet reconstruction (PHDR) algorithm is proposed to reconstruct droplets and to calculate volume on the basis of the contours obtained by the binocular droplet image segmentation algorithm without any symmetry assumptions. The droplet measurement system (DMS) is set up, and a series of experiments are conducted to verify the performance of the proposed method. The results show the advantages of our algorithms, that the volume measurement accuracy is ±3% and that the relative standard uncertainty is better than 2.1%.

This work is to investigate the instrumentation implementing issues of back focal plane (BFP)-typed apertometer. Firstly, we introduce a general instrument architecture of the BFP-typed apertometer, including the hardware (optics and mechanics) of the system, operation procedures of control and measurement system, and also the digital image processing algorithm/software. Secondly, we are the first to discuss the gradual rising effect of total-internal-reflection (TIR) phenomenon, the criteria on how to “exactly” locate the reference ring on BFP images, and the corresponding accuracies. As a significantly important complement, we further discuss three important issues: 1) the influence of Goos–Hanchen shift on numerical aperture (NA) measurement; 2) comparison of one-dimension and two-dimension identification algorithms; and 3) comparison of center locating using Fourier correlation analysis (FCA) and Hough transformation (HT) algorithms.

A rotary laser optoelectronic measurement system is used as part of a multistation network for large-scale metrology. The line-structured laser surface of the transmitter is regarded as an ideal plane for the intersecting measurement. This article presents how the rotary laser surface model can be optimized for large-scale optoelectronic measurement systems. Initially, the deformation of the laser surface caused by the assembly error in a cylindrical lens is analyzed by Zemax simulation and studied by a visual evaluation method based on a high-precision triaxis rotary table. Based on the analysis result, the folded linear surface model and the quadric surface model are applied to reestablish the laser surface model, respectively, to reduce the shape error. A high-precision 3-D coordinate field is designed to acquire an accurate surface parametric model and validate the fitness of the new models. The experimental results based on workshop measurement positioning system (wMPS) show that both optimization models are conducive to improving the fitting accuracy of laser surfaces, and the quadric surface model fits better when the surface shape is closer to the commonest two-folded linear model. Finally, optimizing the laser surface model plays an important role in improving the system measurement accuracy.

Response duration is a key index for evaluating the dynamic performance of a flowmeter. Usually, the duration length can be identified according to the time difference between the start of the change of flow rate into the measured meter and the end of the change of the indicated value. The flow into the meter for dynamic measurement or calibration is also called excitation flow, a change in the short-rise time flow, generated by a dedicated system. Because harsh flow rate variation by the excitation system is particularly difficult to control with high accuracy, changes in the short-rise time flow present immense challenges. The purpose of this article is to study the compensations of strong nonlinear characteristics of the proposed dynamic measurement system. The system includes a piezoelectrically actuated double-nozzle flapper valve and four specific liquid restrictors. The system model is established, which considers the hysteresis behavior of the actuator and the elasticity of the flapper. Simulations under typical conditions are implemented to examine how the hysteresis compensation affects the flow rate response of the system. Experimental data conform to the simulation. Results show that the linearity of the flow rate variation generated by the excitation system considerably improves with compensation on the actuator. The system can respond at approximately 1000 Hz with only 0.5% hysteresis of the actuator. With the hysteresis compensation to the actuator, the flow rate is approximately linear. The flow rate variation is controllable and measurable with the same voltages applied. Higher flow rate variation leads to a shorter response to per unit variation.

In measurement systems, it is essential to have a procedure to obtain not only the calibration curve but also its associated uncertainty for the entire operating range. To achieve it, different alternatives should be taken into account according to the characteristics of the measurement, the way they are taken, the repeatability and reproducibility of the experiments or the nature of the measurement itself. This work presents a step-by-step procedure, to obtain simultaneously the calibration and uncertainty curves of a measurement system, which takes advantage of the maximum likelihood estimation (MLE), the weighted least squares (WLS) method, and the ISO-28037 recommendations. As an application, a U-Bent plastic optical fiber (POF) sensor measuring the sucrose solution density related to the refractive index (RI) is implemented and calibrated according to the proposed procedure.

We had previously proposed a wideband phase measurement system based on the three-voltmeter method using a normal thermal voltage converter (TVC) for measuring the differential ac voltage between two ac voltage signals. Several problems were recorded in our previous system, especially for operations in the wideband frequency range. We have investigated their causes and proposed a few solutions. To overcome these problems, we have proposed an additive calibration for the voltmeters by switching the TVC from the differential input mode into a reversible single-ended input mode. The large error peak problem at higher frequencies has been addressed. We compared our proposed system with the new commercial phase standards up to 1 MHz and confirmed the effectiveness of the additive calibration using the TVC for multiple purposes.

An automatic near-field precision measurement system was proposed in this article. The work was mainly focused on the hardware structure design of the near-field precision measurement system and the software development of the upper computer. At the same time, the electromagnetic field probes used in the system were selected and introduced. The near-field precision measurement system was composed of an upper computer control part, motion controller, power amplifier module, three-axes mechanical arms, spectrum analyzer, and near-field probes. Three-axes mechanical arm, multi-degree-of-freedom fixture, and electromagnetic field probe cooperate with each other for near-field measurement. The electromagnetic radiation emission of high-density integrated module and liquid crystal display (LCD)-printed circuit board (PCB) of laptop computer were measured. According to the measured data, the visual field distribution map was generated, and the measured results were analyzed. Compared with manual measurement method and commercial electromagnetic compatibility (EMC) scanners, the near-field precision measurement system has more accurate measurement results and can accurately locate the noise source.

A fully nonintrusive type ac voltage measurement scheme is presented in this article. Most of the existing noncontact voltage probes require a direct connection to the power system ground. A few other schemes rely on the capacitive coupling between the body of the human operator, holding the probe, and the ground to connect to the power system ground. This is a less reliable method as the direct contact of the hand of the operator to a specified conductive part in the probe is mandatory. Besides, the existing methods do not take care of the effect of the nature of the impedance of the current path through the earth between the human body and the power system ground. In this article, a new measurement approach that provides reliable output from the nonintrusive probe, irrespective of the variations in the probe-to-wire capacitance and impedance between the measurement system and power system ground through the earth, is presented. This includes the capacitive coupling between the measurement system and the earth. A detailed simulation study of the proposed approach has been conducted, and various sources of error and the effects have been quantified. A prototype probe and measurement unit have been developed and tested in the laboratory for a range of distribution voltage (0-600 V), at 50 and 60 Hz. Tests were also conducted in the actual field (distribution voltage). The output was linear with a maximum error of 0.6%.

Light detection and rangings (LiDARs) are considered essential for the environmental sensing required by most advanced driver assistance system (ADAS), including autonomous driving. This has led to significant investments resulted in the availability of countless measuring systems that are increasingly performing and less expensive. Nevertheless, the extremely high speed of light still leads to a nonnegligible quantization error in the direct time-of-flight (ToF) measure at the base of pulsed LiDARs-the leading technology for automotive applications. Hence, pulsed 3-D LiDARs analyze the surrounding by approximating and deforming it on concentric spheres whose radii are quantized with a quantization step that, for most commercial systems, is on the order of some centimeters. The deformation and error introduced by such quantization can thus he significant. In this study, we point out the approximations and assumptions intrinsic to 3-D LiDARs and propose a measurement procedure that, through the analysis of the fine variations of the target position, allows an accurate investigation of the axial resolution and error-probably among the few limitations still affecting this technology. To the best of our knowledge, this is the first study focused on the detailed analysis of the quantization error in 3-D LiDARs. The proposed method has been tested on one of the most popular 3-D LiDARs, namely the MRS 6000 by Sick. The obtained results revealed for the MRS 6000 a quantization step of about 6 cm (ToF quantization of about 0.4 ns) and an axial error normally distributed with experimental standard deviation of about 30 mm.

Frequency extension of the RF power standard using a thermal voltage converter (TVC) has been accomplished down to 1 kHz. To measure the effective efficiency of a thermoelectric power sensor (PS), a reference TVC with a built-in tee is employed. A modified TVC measurement system enables us to automatically measure the dc substituted power of the PS as well as the RF voltage of the reference TVC in terms of RF– dc difference. The standard RF power is obtained from the RF conductance and RF voltage at the input of the PS. A vector network analyzer is used to measure the RF conductance, which causes a significant measurement uncertainty. Associated theoretical consideration and the uncertainty analysis are included. The expanded uncertainty evaluated from the Guide to the Expression of Uncertainty in Measurement (GUM), i.e., the law of propagation of uncertainty is 1.5% ( $k = 1.84$ , 95% level of confidence, trapezoidal distribution) in the frequency range of 1 kHz to 1 MHz. Because the measurement model includes a nonlinear input quantity, the RF conductance, a Monte Carlo method is employed. Simulated results give the measurement uncertainty of 1.6% at a 95% level of confidence, which show good agreement with the GUM.

The combination of a large-field-of-view visual positioning system and a local scanning sensor affords an effective approach to the 3-D measurement of meter-scale objects and has been actively investigated by researchers. The calibration of such an integrated measurement system is essential to establish the overall measurement accuracy. This article proposes to calculate the transformation relationship between the local system and the transfer target through the determination of the scales of the combined system. The principle and implementation of this tracking-based combined measurement system are described in this article, as well as the use of the respective scales of the combined system to establish a model of the applicable geometrical relationships. The Kronecker product was used to solve the model equations, after which homogenous transformation matrix optimization was performed. An error model of the camera-based measurement system was also established based on a combination of the image distortion and the working volume. The 2-D and 3-D errors of the local and global sensors were further quantitatively simulated and visualized to demonstrate the calibration accuracy. Standard plane and complex large object measurement experiments were performed to verify the accuracy of the proposed measurement system and its use for the reconstruction of a large shape.

In this study, a novel low unity-gain frequency and low power consumption instrumentation amplifier (UGFPCIA) was designed and applied to the readout circuit of the potentiometric biosensor measurement system. The proposed UGFPCIA was developed using the Taiwan Semiconductor Manufacturing Company (TSMC) 0.18- $\mu \text{m}$ process technology, and simulated in a Laker analog design environment, and had a 1.5-V supply voltage for reduced power consumption. The uric acid (UA) biosensor based on RuO2 thin film was fabricated in this study. The sensing characteristics of the RuO2 UA biosensor were measured by the proposed UGFPCIA and the LT1167, a commercial instrumentation amplifier; then, their readout circuits were compared. According to the chip measurement results, the proposed UGFPCIA achieved a common-mode gain of −54 dB and a unity-gain frequency (UGF) of 588 kHz. Its power consumption was $397.92~\mu \text{W}$ . Moreover, the measurement results showed that the sensitivity and linearity of the flexible arrayed RuO2 UA biosensor were 7.15 mV/(mg/dL) and 0.997, respectively. The LT1167 used a 2.3-V minimum supply voltage, while the proposed UGFPCIA used a 1.5-V minimum supply voltage; the power consumption is 84% lower than the former. This indicates that UGFPCIA was more stable during the measurement process and consumes lesser power.

Visualization and measurement for civil structure have been a constant field of research. Typically, 3-D measurement systems are static instruments that offer low degrees of flexible motion and require a significant amount of time for successful 3-D measurement. In this article, a machine vision system is developed to facilitate the 3-D measurements and reconstruction process. The proposed method depends on multimobile robots to achieve a portable 3-D measurement and reconstruction system. It consists of a 3-D reconstruction and measurement pipeline, which deploys multiple vision sensors mounted on teleoperated mobile to acquire the 3-D scan and 2-D image data. It can operate in both indoor and outdoor environments as for each structure a sequence of images and LiDAR scans are processed. The outcomes of the proposed method are a 3-D visualization for the structure along with its dimensional and volumetric measurements. The performance of the proposed system is evaluated using indoor and outdoor experiments to validate its application for measuring real structures. The results obtained showed the robustness and mobility of the proposed method.

Large-scale complex surfaces are the core components of large aircraft, ships, and wind turbine generators. High-accuracy manufacturing of the components is very crucial for its performance. Automated and high-accuracy large-scale 3-D measurement is an effective means for the manufacturing accuracy control of these components. This article proposes an automated mobile robotic profile measurement method for large-scale complex surfaces, and it also proposes a high-accuracy point clouds alignment algorithm to improve the measurement accuracy. A fringe projection scanner, integrated on the end of a mobile robot, is utilized to scan the surface and obtain the local scanning point clouds. The local scanning point clouds’ coarse alignment is implemented using the robot’s joint data and the laser sensor’s positioning data. After that, a fine alignment algorithm combining the fruit fly optimization algorithm (FOA) with the improved iterative closest point (IICP) algorithm is proposed for point clouds’ fine alignment. Practical measurement was performed on a sectional wind turbine blade, and a broad region of $4.6 \text { m} \times 2.6$ m was measured. An accuracy evaluation method based on point-to-plane distance was adopted to evaluate the measurement error. The result that the mean distance error is less than 0.4 mm shows the proposed mobile robotic measurement system and the aligning method are of high accuracy.

The accurate measurement of the transient fault voltage is helpful to the control, protection, condition monitoring, and evaluation of the power system. In this article, a simple and economical method for measuring the transient fault voltage based on the electric induction of a metal slice is proposed. The frequency spectrums of the transient fault voltage and the surge voltage of 10/ $700~\mu \text{s}$ are compared. The surge voltage of 10/ $700~\mu \text{s}$ is selected as the excitation source to mimic the transient fault voltage in the simulation and experiment. A simple coaxial experimental model for mimicking the gas-insulated switchgear (GIS) is built. Two schemes for the metal slice are designed and fabricated on the earthed enclosure. The equivalent circuit of the measurement system is established. The capacitance parameters in the equivalent circuit are calculated by the finite element method. Based on the equivalent circuit, the transfer relationship between the measured voltage and the induced voltage is given. The effect of the parameters of the equivalent circuit on the surge voltage measurement is discussed. The effectiveness of the method is verified by both simulation and experiment. The sensing part of the proposed method has the advantages of low cost and no insulation problems. The proposed method can be directly used in GIS.

The performance of a high-voltage switching impulse (SI) measurement system is highly dependent on the characteristics of the used voltage divider. Self-built or commercial voltage dividers do not always fulfill the requirements set for reference-level devices. Software corrections to improve the non-ideal divider response are easy to implement. This article describes the traceability and performance of the SI measurement systems of VTT MIKES up to 400 kV. Traceability is based on a calculable impulse voltage calibrator, which is used for calibration of a reference digitizer and a 10-kV divider. The 10-kV divider is then used to calibrate the 400-kV modular divider. Responses of both dividers are corrected using two different software methods. Implementation of these software methods allows state-of-the-art impulse parameter uncertainties. The most significant uncertainty component of time to peak is related to its definition and evaluation according to IEC 60060-1:2010 and IEC 61083-2:2013.

This article proposes a novel simplified model that describes the real part (in-phase component) of the difference in pickup coil voltage when an eddy current (EC) sensor consisting of two coils (excitation and pickup coils) is placed above the titanium (Ti) alloy sheet. A parameter that encapsulates the coil geometry factors is integrated into the classical Dodd–Deeds model, and then, the model is simplified by combining with the electromagnetic properties of Ti alloy. The use of the simplified model provides a thickness measurement method for Ti alloy sheets. The measured thickness can be calculated directly from the calibration signal by using the model, without the need to predict response by solving the forward model in advance. Experimental measurements were conducted on TC4 (Ti-6Al-4V) Ti alloy sheets of different thicknesses with a developed EC sensor and measurement system. The experiment verified the proposed model and measurement method. The experimental results shown that the maximum measurement error is less than 2.86%, which is greatly lower than the permissible error of the current industry standard. This study provides a theoretical basis and a fast method for EC thickness measurement of Ti alloy.

In this work, we propose a real-time noncontact thickness measurement system for conductive materials based on an inductor–capacitor ( LC ) resonant eddy-current sensor. For the aluminum, copper, stainless steel 304, and carbon steel samples of various thicknesses, the in-phase and quadrature components of the sensor output taken during liftoff scans are found to be a series of quadratic-like curves on the phase versus logarithmic amplitude diagram. These curves can be used to generate the standard phase–amplitude relations for thickness conversion. The phase–amplitude relations of the thickness between the values of standard samples are calculated by cubic spline interpolation. With the standard database of phase–amplitude relations, the noncontact thickness measurement was implemented in real time for the copper foil sample with an error of ±3% when the liftoff distance is less than 5 mm. The liftoff tolerance is as large as 100% of the probe diameter, indicating that the proposed method is useful for online quality inspection of conductor films on flexible substrates.

This article presents an amplitude and 360° phase shift array measurement system. The basic cell of the measurement system uses a novel amplitude and phase detector based on switched dual multipliers. The phase shift measurement is characterized using an analog phase detector (mixer), detecting a maximum range of ±90°, and a double multiplication of the input signals, in phase and phase shifted. This method broadens the frequency and amplitude range beyond other solutions that require fulfilling the quadrature condition. This method broadens the frequency and amplitude beyond other solutions requiring fulfilling the quadrature condition or phase and amplitude balance. Thus, it enables to compensate significant phase imbalance in the 90° hybrid or use amplitudes out of the range that ensures the switching operation of mixer diodes. The circuit calibration that allows compensation for errors (amplitude, phase shift, mismatching, etc.) is detailed, and its relation to the required measurement accuracy is discussed. The design can be easily extrapolated to other frequency ranges because it uses commercial RF devices available in a wide frequency range and avoids the need of crossing lines or complex 90° hybrid. A prototype with $3 \times 3$ cells has been built to evaluate various test conditions on $1 \times 3$ cell configurations that show the advantages of the procedure. It should be highlighted that the cell prototype uses devices that will be operating outside the frequency and amplitude ranges recommended by their manufacturers. A calibration from 2.6 to 6 GHz and −15 to −3 dBm was performed to evaluate the measurement errors. An analysis of the isolation between cells and different calibration configurations is performed to analyze the measurement errors. Measurements show compensation of +30°/−25° phase imbalance and 13-dB power lower than mixer manufacturer recommendation.

The admittance-type-level sensor is used for continuous level measurement in both metallic and nonmetallic tanks. However, the use of this sensor is limited because of the significant nonlinearity and cross-sensitivity. In this work, the authors have proposed the concept of a double-electrode admittance-type-level sensor. The said level sensor measures the level and the temperature of a conductive liquid. The multifunctional measurement is possible by the detection of the extent of cross-sensitivity using fuzzy logic and decomposition of the measurement variables. The experimental prototype of the sensor and associated instrumentation have been developed, and from the experimental results, it is found that the error in the measurement is consistently distributed and within the range of 1.86% for the level and 2.73% for temperature, which demonstrates the appropriateness of the design. This measurement system and sensor design can be implemented in the boiler-drum-level measurement for better drum-level control.

In a thermal power plant, online measurement of the size distribution of pneumatically conveyed pulverized fuel is essential for the improvement of combustion efficiency and the reduction of pollutant emissions. In this article, an innovative instrumentation system based on acoustic emission (AE) detection and triboelectric sensing is proposed for the on-line continuous measurement of particle size distribution. With a waveguide protruding into the flow, the AE signal is generated from the impacts of particles with the waveguide. The peak voltage of the AE signal is related to the particle size and impact velocity. For the first time, two triboelectric sensor arrays each with three arc-shaped electrodes near to the waveguide are used to measure the impact velocity. Meanwhile, a novel particle sizing algorithm with Gaussian prediction is proposed to reduce the effect of overlapping impacts and environmental noise on the peak distribution. With the known impact velocity measured from the triboelectric sensor arrays and the modified peak distribution, the measurement of particle size distribution is achieved. Experimental tests were conducted on a gas–solids two-phase flow rig to assess the performance of the developed measurement system. Silica sands in three size ranges of 116–750, 61–395, and 10– $246~\mu \text{m}$ , respectively, were used as test particles. The experimental results demonstrate that Spearman’s rank correlation coefficients between the measured and reference size distributions for all test particles are all greater than 0.8, while the discrepancy for each particle size segment is within ±4.8%.

Accurate measurement of flow parameters of multiphase flow has great significance for safe, economic, and efficient operation of the industrial production process. To simultaneously measure the water holdup and velocity, a combined electrical and ultrasonic Doppler measurement system based on a compact peripheral component interconnect (CPCI) bus is designed. The combined sensor consists of a six-ring conductance sensor, two pairs of capacitance plate sensors, and an ultrasonic Doppler sensor. The measurement system is cored with a field-programmable gate array (FPGA) and consists of a series of functional modules. Through flexible programming and interboard communication, the system can meet different measurement requirements. To meet industrial data transmission standards and increase system extensibility, the demodulated data are transmitted to a host computer through the CPCI bus for further data analysis. Dynamic experiments demonstrated that the multimodal system has stable and preferable performance in water holdup and velocity measurement under all flow patterns. The conductance and capacitance sensor could realize the water holdup measurement with the root-mean-square error (RMSE) of 3.02% and the overall superficial velocity estimation through cross correlation with the RMSE of 0.09 m/s. Besides, the pulse ultrasonic Doppler transducer could measure the overall superficial velocity through the area integration of the velocity profile with the RMSE of 0.08 m/s.

An important task in biomechanics is human body articulations’ internal torques measurement. This is known as a kinetic or inverse-dynamics problem. Its solution requires a combination of kinematic and dynamic measurements with a biomechanical model, involving subject-related anthropometric parameters. The uncertainty-evaluation thereof is here considered. The method poses on a probabilistic model of the associated measurement system, according to the “Guide to the expression of uncertainty in measurement” general principles. We consider a comprehensive set of influence quantities, including markers’ misplacement or parasite movements. The anthropometric parameters’ uncertainty is discussed in detail. The proposed approach helps to identify the most influential experimental factors.

Deflectometry is a promising method for the in situ measurement of specular surfaces. However, the accuracy of this method largely depends on the geometrical calibration, which suffers from a low convergence rate and local minima during the optimization. Off-machine calibration results in a change in geometry parameters due to the repeated disassembly of the measurement system and change of ambient temperature, which largely affects the measurement accuracy. This article presents a flexible on-machine calibration method with fewer intermediate parameters to accelerate the optimization for the in situ stereo deflectometry system. An inclined mirror with a fixed angle was mounted on the spindle of an ultraprecision machine tool and used as a reference plane reflecting the fringe displayed on the display screen. The reflected fringe captured by the cameras was encoded by an inclined mirror moving along the $C$ -axis and the $Z$ -axis of the machine tool. The preknowledge of the movement distance of the ultraprecision machine tool along the $Z$ -axis and rotation angle of the spindle with a nanoscale accuracy was used to largely reduce the number of intermediate variables involved in the optimization, thus improving the convergence speed of the global optimization method and calibration reliability. The experiment results show that this calibration method has higher calibration accuracy, measurement accuracy, and reliability compared to the conventional off-machine calibration method.

This article presents a standard field generation system with an antenna for the calibration of a Ka-band electric-field probe. We constructed a measurement system having capability of not only rotating the azimuth angle of the probe but also changing the separation distance between the antenna and the probe. As a result, the orientation and separation distance of the probe can be suggested for minimal variation of the measurand, which reduces the overall uncertainty. For traceable electric-field strength measurements, we measured the associated quantities of the power, antenna gain, and impedance of the individual components constituting the field generation system. An evaluation of the uncertainty of the components providing traceability to the system was also conducted. The system is expected to generate a standard field higher than 10 V/m in the frequency range of 26.5–40 GHz. Uncertainty in the correction factors is quantified to determine the factors that affect the calibration, and the expanded uncertainty of the standard field generation system is found to be 5.1% at 26.5 GHz and 5.3% at both 33 and 40 GHz.

This article proposes a novel method for estimating multiharmonic sources in the underdetermined measurement system. In the proposed methodology, supposing that the number of harmonic measurements (HMs) is less than that of unknown state variables, the HM system can be mathematically described as underdetermined matrix equations, which has infinitely many solutions corresponding to all possibilities of the locations and the current emissions of the actual harmonic sources. Because the harmonic current emissions from nonharmonic source buses are approximately zero, by fitting the harmonic current emission of every possible nonharmonic source bus combinations and selecting the minimum fitting residual of all combination cases, thus, the true number, locations, and current emissions of harmonic sources are determined. Compared with the existing methods, the proposed method has less dependence on the placement of HMs and requires less prior information of harmonic sources. The effectiveness of the proposed method is verified by simulation and field case, with respect to a high correct location rate of more than 90%.

Indoor positioning approaches are often based on electromagnetic wave signals with high frequency. However, signal reflections and the corresponding signal superpositions are challenging. As a result, there is still no indoor positioning technology established in commercial products, such as smartphones or smartwatches. Recent publications have shown that this indoor positioning problem can be addressed by using artificial magnetic fields. However, the cubic attenuation of the magnetic field challenges technical implementations and limits the ranges. In this work, we propose an approach striving to address these issues of magnetic indoor positioning via a simple electromechanical single-anchor concept in combination with a small wearable sensor circuitry. The terrestrial magnetic field together with amplitude and phase measurements resolves the position and the orientation of the tag. The proposed indoor positioning approach via artificial magnetic fields is tested in a corridor for a spatial region of approximately 100 m2. The mean positioning error in this experiment was calculated to be $\mu =1.0\pm 0.81\,\,\mathrm {m}$ . The proposed indoor positioning approach via artificial magnetic fields and the corresponding measurement system can, therefore, be useful alternatives when considering applications in which simple implementation is more important than positioning precision.

The IVT for power frequency is an essential facility in the power system. Due to the requirement for high-voltage insulation, the sensing part of the conventional IVTs is bulky and costly. The purpose of this article is to propose a new voltage measurement method based on capacitive voltage divider for GIS. The equivalent circuit of the measurement method is built. The numerical simulation model for the measurement system is built based on the actual size of GIS with rated voltage of 220 kV. And FEM is employed to analyze the transfer relation and the accuracy of the proposed measurement method. The experiments are conducted in the laboratory and at an actual GIS platform, respectively. The transfer relation between the applied voltage and the induced voltage is obtained. Compared with conventional IVTs, the dimension of the measurement system is very small. Due to the low voltage of the sensing part, the insulation problem of the sensing part is avoided. And due to simple structure and linear characteristics, the transfer relation of the proposed measurement system can be obtained with high accuracy.

In a temperature-controlled radio frequency (RF) power measurement system, there is a temperature difference between the system and the environment temperature. If a metal waveguide is used in the system, heat can reach the core of the system and affect the measurement. An adiabatic waveguide is utilized to reduce this heat flow. This article introduces several WR10 rectangular waveguides that are used in the Korea Research Institute of Standards and Science (KRISS) microcalorimeter and an evaluation system that can measure the adiabatic performance of the waveguides via a thermostat. The basic concept and measurement setup for the evaluation system are briefly introduced, and the structure and the function of the waveguide heat source and heat sense modules of the thermostat are presented. The test results of the adiabatic performance of several WR10 rectangular waveguides are compared and the electromagnetic performance is presented. We also tested preliminary dielectric waveguides that have been co-studied with Physikalisch-Technische Bundesanstalt (PTB), Germany recently. We propose an index to characterize the adiabatic performance of the waveguides. Based on the index results, we improve the adiabatic performance of our newly electroforming-processed adiabatic waveguide with a thick resin coating, which is forty times higher than that of the prototype KRISS microcalorimeter adiabatic waveguide. Finally, we fabricated and investigated dielectric waveguides that have a superb adiabatic property for the microcalorimeter application.

The article presents the findings of main recent research and development works conducted for gas leak detection and measurement. Higher emphasis are considered for 2-D arrays sensors because of the wider coverage area they can handle in real-time, especially if they are carried within moving vehicles such as drones, helicopters, and satellites. This includes long-wave infrared (LWIR)- and medium-wave infrared (MWIR)-imaging systems. In spite of their success to accurately detect, localize, and even quantify leaks, under certain conditions, LWIR and MWIR imaging systems still face several challenges. This prevented them to continuously operate in all environmental conditions and within a reasonable long period of time. Thus, the article also presents other alternative technologies which can potentially complement or substitute LWIR and MWIR techniques. This includes photoacoustic, temperature profiling, and short-wave infrared (SWIR)-based techniques. The article can be a useful resource to help deciding which of these techniques can be used for a particular gas leak-detection application.

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.

In this article, we proposed a measurement system that can simultaneously measure temperature and pressure. By analyzing several existing measurement methods of the sensor, we determined that the resonance frequency and $S_{11}$ (reflection coefficient) amplitude of the sensor readout system should be measured when the resonance frequency of the sensor up to a hundred megahertz or even gigahertz and when the sensor works in ultrahigh temperature environment. In addition, we designed a simple and accurate sensor readout circuit and an LC temperature–pressure sensor. By analyzing the resonance frequency and the amplitude of $S_{11}$ , temperature and pressure were measured simultaneously with a single LC circuit. Since the analysis of the whole nonlinear system of sensors is complex, we divide the entire nonlinear system into several linear systems superposition. By analyzing the interference between temperature and pressure, we further optimized the measurement method. The relative errors of the temperature measurements in the range of 25 °C–300 °C and 300 °C–1000 °C were only 2.89% and 1.25%, respectively. From 25 °C to 300 °C and 300 °C to 1000 °C, the average relative errors of pressure measurement were only 4.07% and 4.74%, respectively. Besides, the proposed method can also be widely used in the measurement of LC multiparameter sensors.

For fringe projection profilometry (FPP), the nonlinear response of the camera and projector in a 3-D measurement system causes the captured fringe to be nonsinusoidal, which results in periodic phase errors. This article reports a theoretical analysis of the phase error caused by the nonsinusoidal fringe and proposes a triple $N$ -step phase shift (PS) algorithm. Experimental results demonstrate that the proposed algorithm outperforms the existing double $N$ -step PS algorithm in terms of reducing the phase error caused by the nonsinusoidal captured fringe.

This article reports the investigation results of long-term stability tests on on-wafer measurement systems in frequency ranges up to 325 GHz conducted by the NMIJ-AIST. The radio frequency (RF) probe coordinates in the $X$ -, $Y$ -, and $Z$ -directions, and the tilt angle is automatically adjusted by performing RF signal detection. Calibrations and verification processes were repeated for over a year. The novelty of the study is that it optimizes measurement procedures for the test, demonstrates a long-term stability test, and compares the evaluated long-term stability to the effects of probe model, absorber, and calibration method. The standard deviation of the measured reflection coefficient ranged between −32 to −70 dB in magnitude, and 0°–10° in phase. The standard deviation of the measured transmission coefficient ranged from −43 to −80 dB and from 0.2°–2.7° in phase. The refined procedures contributed to improve the measurement reproducibility compared to the previous report. Furthermore, the effects of the chuck material and the calibration method were larger than long-term stability.

High-precision remaining wall thickness is desirable in the mirror milling of large thin-walled parts. However, the workpiece deformation caused by sheet forming, clamping, and self-gravity makes it difficult to control the thickness if the original tool path generated from the designed CAD model is used directly. In order to solve this problem, the deformed workpiece surface is supposed to be reconstructed, and the original tool path should then be adjusted. In this article, based on a self-developed multiprobe ultrasonic measurement system, an autonomous profile tracking approach, mainly including adaptive sampling point prediction, boundary processing, and feature point extraction, is proposed to scan the deformed surface. The sampling point prediction algorithm calculates the position and orientation simultaneously for the next sampling point. In particular, a current-measurement-output-based orientation prediction algorithm is proposed to guarantee the autonomy of the profile tracking, and a reference-measurement-point-based orientation prediction algorithm is proposed to improve the prediction accuracy. The boundary processing algorithm controls the scanning direction and ensures that the sampling process is implemented inside the measurement boundary. The online feature point extraction algorithm reduces the redundant points for the following surface reconstruction. Practical experiments on freeform surfaces with/without complex boundaries verified the feasibility and effectiveness of the proposed method.

In-plane retardation and out-of-plane retardation by optically anisotropic medium are generally measured with the Mueller polarimeter. We proposed a method for measuring the in-plane retardation and out-of-plane retardation using the Stokes polarimeter. The suggested method requires no polarization state generator, simplifying the measurement system. The retardation measured with the Stokes polarimeter was compared with the data measured with the Mueller polarimeter, and their difference was less than 2.5 nm ( $0.005\lambda$ ). In addition, the suggested method can find the orientation of the slow axis of the retarder and the order of retardation. Although the conventional methods require measurements at multiple wavelengths to distinguish the order of the retardation, the suggested method can find the exact retardation using data at a single wavelength of light.

During unicondylar knee arthroplasty surgery, the tibial prosthesis is fixed and the angle of distal femoral prosthesis relative to the prosthetic gasket is changed to generate the force line trajectory, which is important for doctors to judge the appropriate position of the implants. In this article, we propose a wireless force line trajectory measurement system for unicondylar knee arthroplasty, which includes the pressure sensors array, the control and processing data circuits, the radio frequency transmitter, and the data recorder. Data from 20 sensors are processed and transmitted wirelessly, and the force line trajectory is displayed on the screen in real time. The least squares fitting algorithm is proposed, with which we obtain the pressure distribution, the maximum pressure points, and the force line trajectory. We adopt field programmable gate array to implement the algorithm with lower–upper decomposition to fit the trajectory faster and transmit less data to save power. The average current consumption of the system is 1.37 mA in the operating mode. Dimensions of the data transmission module are length 70 mm, width 35 mm, and height 4 mm. The total uncertainty of the system measurement force line trajectory is 0.92 mm. Experimental results show that the system meets the requirement of real-time measurement of the force line trajectory during the surgery.

The measurement of the electromagnetic reflection characteristics of a device under test (DUT) is of interest in a large variety of applications. For this task, the established low-cost approach of using pulse-shaped excitation signals is more and more replaced by employing continuous binary coded excitation signals. The reason behind this is that reflection measurement systems with continuous signals offer a larger signal-to-noise ratio (SNR), which allows for a larger dynamic range compared to pulsed systems for the same measurement time. However, a correlator is needed to access the impulse response function (IRF) of the DUT. In this contribution, a reflection measurement system is presented using a hybrid correlation approach. In the latter, the correlation is performed using a combination of a hardware and a software correlator. The hardware of the developed measurement system has been optimized to achieve a high dynamic range and a high measurement accuracy. A demonstrator system has been realized using the so-called almost perfect auto-correlation sequences (APASs) with a chip clock of 5Gchips/s. With the optimized hardware, a dynamic range of 82 dB has been achieved. The measurement accuracy has been validated by means of distance measurements versus a high accuracy laser reference system achieving a maximum error of 25 ${\mu }\text{m}$ . Furthermore, the measured reflection coefficient of a low-pass filter has been compared with the results obtained with a vector network analyzer (VNA).

This article presents a portable and programmable frequency measurement system (PrO-FMS) with 0.1-ppm RMSE resolution over a measurement time interval of 33.2 s for bulk-acoustic resonator applications. PrO-FMS has a feature of choosing a frequency estimation method and accordingly the sampling frequency, which is programmable. Five frequency estimation methods, Candan, Djukanovic, Prony, M-Pisarenko, and zero crossing interpolation methods, are reviewed for high-resolution frequency measurement. PrO-FMS can also be reconfigured to select a particular resonance mode over a range of 1–10 MHz. Measurement results are provided for two different commercial quartz crystals and a microfabricated in-plane bulk acoustic resonator in two different modes of resonance. The results of these estimation methods are compared with a standard commercial tabletop frequency counter. Measurement results show that PrO-FMS can achieve a resolution of 0.1 ppm RMSE. For the same gate time, PrO-FMS provides better resolution than standard tabletop frequency counter. This article also provides a study on the behavior of the five different frequency estimation methods for short- and long-term measurements for quartz crystals and bulk acoustic resonator in two different modes.

The revised International System of Units has been implemented on May 20, 2019, and now, the Kibble/joule balance can be used to achieve the traceability of mass to the Planck constant. In principle, the Kibble/joule balance can be operated in three measurement schemes, in which the one-mode one-measurement phase (OMOP) scheme has obvious advantages over the other two schemes. The OMOP scheme was first proposed and tried in the Kibble balance, but due to the mutual interference between weighing and velocity measurements, the achieved mass/Planck constant measurement uncertainty did not match the goal of $5 \, \times \,10^{-8}$ . However, the mentioned interference can be well suppressed in the joule balance based on its quasi-static measurement characteristic. Therefore, the feasibility of the OMOP joule balance is analyzed in this article, and the measurement sequence is introduced in detail. Three factors involved in the OMOP joule balance that may affect the final mass measurement uncertainty are analyzed and demonstrated, i.e., the consistency of the two independent coils of the bifilar coil, the current effect of the special coil system, and the performance of the improved flux linkage difference measurement system. Besides, it is found that the stability of excitation current decreases significantly due to the movement of the magnet system, but the theoretical analysis shows that this does not affect the measurement result of the OMOP joule balance.

Tool condition monitoring (TCM) has been a constant field of research. Conventionally, some sensors are installed at specific parts of the machine, and by using the signal-processing techniques, the tool wear is estimated. In this article, a direct system based on image analysis has been developed to automate the in-process tool wear measurement. The method uses only a single camera installed inside the machine and a tree-stage measurement process composed of image treatment, image comparison, and wear measurement. Experimental results show that the detection of similar images has a success index rate (SIR) equal to 98.89%, whereas the measurement error of the average flank wear and the maximum flank wear is estimated to be 3.57% and 2.92%, respectively.

This article aims to develop a reliable automatic measurement system to measure the geometry parameters of the cross section of cigarette filter rods. To achieve this purpose, an automatic measurement system based on machine vision is constructed. This measurement procedure is divided into three stages: initial stage, cutting stage, and measurement stage. In the measurement stage, a robust and accurate measurement approach is proposed to measure the depth, number of grooves, and area ratio of grooves to the section for different kinds of cigarette filter rods. First, a dynamic location algorithm is proposed to solve the position error of the mechanical system based on template matching. Subsequently, considering the uncertainty of the shape of the grooves, the iterative groove identification based on convex hull (IGICH) algorithm is constructed to detect correctly the grooves using three features: the area, width, and distance of groove distribution for the connected regions. Next, we have presented the section geometry parameter measurement method according to quality control requirements. Moreover, the system calibration algorithm is developed to improve the system accuracy based on the telecentric lens principle. Finally, based on the experimental setup, detailed characterizations including efficiency, precision, and robust analysis were performed. The results show that the proposed system can adapt to the automatic, precise, and robust measurement of geometry parameters for the section of different kinds of cigarette filter rods, and satisfy the measurement accuracy and speed required by quality control.

Resistance spot welding (RSW) is the predominate joining method used for steel auto body assembly. Significant effort has been made to control and inspect the RSW quality in real time to guarantee the security and the reliability of body structure joints. Among the various methods, monitoring of the surface indentation is proven to be a promising method to actualize online weld quality assessment. In this article, a new approach to online measurement of indentation depth for the RSW process using a servo gun is proposed. The approach entails the development of a modified measurement system to eliminate the transmission error of the toothed belt drive and compensate the deflection of the fixed electrode arm, which enables precision measurement of the electrode tip displacement (ETD). Furthermore, consideration is given to explaining the downtrend of the displacement curve during the hold time within the RSW process, and the indentation depth at ambient temperature is finally estimated through curve fitting and experimental correction. The experimental results show that the error of indentation estimation could be limited to $\pm 30~\mu \text{m}$ ( $\pm 2\sigma$ ) at 95% confidence level, which far surpasses the performance of the previous method. Based upon sensitivity analysis, the precision is proven to be robust to different workpieces ranging from low-carbon steel to high-strength steel.

This paper presents an experimental method for investigating the dependence of critical current on the applied magnetic-field intensity and the angular orientation in high-temperature superconductor (HTS) tapes and cables. Comparisons between critical-current measured and simulated data are presented as a function of field angular orientation. The obtained relation can be used as input data for numerical calculations or simulations for designing application devices that utilize HTS tapes and cables.

Embedded impedance spectroscopy is gaining importance in the Internet of Things (IoT) era, where a new class of impedance spectroscopy devices is needed to fulfill a suitable frequency range, size, power consumption, and costs. In this paper, we investigate the feasibility of embedded impedance spectroscopy measurement systems with a focus on power-aware systems. We propose a novel embedded architecture based on a low-cost microcontroller and using a reduced number of electronic components. In order to enable the system for measuring higher frequencies up to 10 MHz, we use the undersampling technique on a relatively simple microcontroller with 12-bit in-built analog-to-digital converters and a sampling rate of 1 mega samples per seconds (MSPs). For the impedance calculation in the range of $100~\Omega -1 \text{M}\Omega $ , the Discrete Fourier Transform (DFT) is implemented directly on the same microcontroller. The experimental validation shows a maximal standard deviation of 0.5% in amplitude measurement and a standard deviation of 0.55° in phase measurement, which are sufficient for various applications of wearable solutions. The system design provides an outstanding performance considering low-cost, small foot print, and low-power consumption.

This paper presents the design and implementation details of a complete noncontact (NC) voltage acquisition system, which allows the measurement of power-line voltage waveforms without galvanic contact. The system is composed by a novel capacitive probe, an analog front end (AFE), and a microcontroller-based digital signal processing stage. A deep experimental characterization of the noncontact measurement system was performed. The tests reported a high linearity (maximum nonlinearity of ±0.2%), a low input-referred noise (11 mVrms), and a low-frequency response distortion. Measurements of ±330-V triangular waveform signals were performed with maximum instantaneous errors below ±1.5 V. The power-line voltage (220 Vrms at 50 Hz) was acquired without galvanic contact with an instantaneous error lower than ±3 V, whereas the mean error on rms voltage measurements was 0.32% and the maximum 0.7%. A two-day continuous measurement of power-line voltage was accomplished for testing system's stability, resulting in negligible accuracy variations. Fil: Haberman, Marcelo Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales. Universidad Nacional de La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales; Argentina Fil: Spinelli, Enrique Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales. Universidad Nacional de La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales; Argentina

Low-cost ultrasonic sensors are widely used for non-contact distance measurement problems. Speed of ultrasonic waves is greatly affected by environmental conditions such as temperature and relative humidity among a few other parameters. Presence of acoustic and electronic noise also influences an ultrasonic sensor based distance measurement system. Existing standard techniques assume that the temperature and relative humidity levels remain constant throughout the measurement medium. In our proposed system, we measure water level in storage tanks of different depths, which exhibits a gradient of temperature and relative humidity across the measurement medium. Hence, the standard ultrasonic measurement system (UMS) is not able to estimate distance accurately. In this article, we propose an algorithm based on modified neural network architecture to increase the accuracy of UMS and also to extend the standard operating range of the ultrasonic sensor used. This article presents a novel approach to reduce measurement error using Levenberg–Marquardt backpropagation artificial neural network (LMBP-ANN) architecture. The proposed model is validated by comparing the actual water level at various depths under different environmental conditions with the output of the trained neural network. The measurement error in the proposed model is bounded by ±1 cm in the distance measurements ranging from 2 to 500 cm. This model is able to extend the maximum standard operating range of the ultrasonic sensor (HC-SR04 model) from 400 to 500 cm. The proposed model is evaluated using mean squared error (MSE) and $R$ -values to establish the effectiveness.

We propose the optimal design of passive devices that can be used to verify on-wafer noise parameter measurement systems. The design principles result from obtaining the minimum relative uncertainties of four noise parameters: $F_{\mathrm {min}}$ , $R_{\mathbf {n}}$ , $\vert \Gamma _{\mathrm {opt}} \vert $ , and $\angle \Gamma _{\mathrm {opt}}$ for a wide range of S-parameters of a passive two-port network. A Monte Carlo method has been used for the investigation, and simulation results show that $\vert S_{11} \vert $ plays a primary role in deciding the optimal design and must be within 0.5– $0.6.~\vert S_{21} \vert $ plays a secondary role in the design and, ideally, it should be as small as possible. Based on these findings, we designed and fabricated three planar attenuators on a semi-insulating GaAs substrate. The test results (at up to 40 GHz) show excellent agreement with the simulation. This is the first time that the effect of different designs of passive verification devices on the system noise measurement has been analyzed, and the design principles of optimal passive devices are given.

It is known that the distorted electric field is generated by a high-voltage alternating current (HVac) transmission line passing through a conductor, but few studies have accurately measured and analyzed it. In this article, we analyze the distorted electric field and distortion rate (DR) using a ZigBee-based optical measurement system. First, the key parameters of the integrated optical sensor (IOS) and the wireless module are discussed, respectively. Second, the plate–plate and ball–plate characteristics of the measurement system are studied, and the results show that the measurement system can accurately measure the uniform and nonuniform electric field within 25 kV/m. Third, the measurements are compared to the calculation values, and the results show that the relative error is within 12%. Finally, the distribution law of DRs when considering the grounded shielding wire and height of the obstacle is analyzed. The findings show that the DR varies with the height of the obstacle but is not affected by the grounded shielding wire.

This paper deals with the development of a simple, low-cost, fringing field impedance sensor suitable for early age hydration monitoring and setting time determination of hydraulic cement paste. An impedance technique using a double-sided copper-cladded printed circuit board substrate as a sensor is proposed. Different batches of sensors with different probe sizes and substrate thickness have been fabricated and tested for hydraulic cement paste. The cement samples having different water-to-cement ratios (w:c) by weight are considered to study the effectiveness of the sensor. The purpose of this study is to develop a simple yet effective measurement system to determine the change in impedance of the cement paste with hydration time and thus to correlate the impedance change to determine the critical initial and final setting times. Initial and final hydration times of different cement samples are compared with the results of the commercial Vicat apparatus (VA). The values of the setting times closely match the Vicat values (the average value at 100 kHz differs by 4 m). Therefore, the proposed sensor-based system can be used in place of conventional VA to determine the hydration condition. The output of the sensor can be electronically processed further to develop a prototype system.