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• Based on the principle of torsion balance, a micro-force sensor was designed. The minmum force resolution reaches to 0.14μN. • An in-situ dynamic calibration method was adopted to obtain the value of the torsional constant K. • The interaction force between a slender cylinder imitating the leg of a water strider and the water surface is measured. A micro-force measuring system with a resolution of micro-Newton based on the principle of torsion balance is developed, which consists of micro-force sensor, linear motor, specimen platform and the matching measurement and control software based on LabVIEW. The dynamic method of calibrating the micro-force sensor by in-situ vibration was used to overcome the influence of boundary conditions such as the rod and the clamp, achieving an accurate calibration of the torsional constant. The system was applied to study the process of pressing a slender cylinder imitating the leg of a water strider into the water surface. The results show that the critical interaction force per unit volume of the slender cylinder decreases with the increase of its diameter, showing a significant size effect; the critical depth and critical interaction force can be increased by spraying superhydrophobic silica coating, which greatly improves the hydrophobic performance of the slender cylinder. [ABSTRACT FROM AUTHOR]

When using vision systems that employ multiple spectral bandwidths, such as visible and Long-Wave Infrared (LWIR) bands, the calibration object's appearance can significantly impact the matching of common features in the images. To address this issue, a robust calibration technique is necessary to work with reflections and the degraded appearance of the calibration pattern over time. In this paper, we propose a novel stereo calibration technique that can be used for visible-thermal imaging systems for remote sensing applications (e.g., mounted on Unmanned Aerial Vehicles, UAVs). Proposed method can be used on a generic calibration pattern, and we exploit computer vision algorithms to accurately estimate the intrinsic and extrinsic parameters. The algorithm can mitigate specular reflections and contrast inversion issues that may degrade the calibration accuracy. The calibration technique is designed to be versatile as it operates also in outdoor environments, hence it can be especially useful for UAV applications since on-field re-calibration is often needed. The proposed method has been validated using two different calibration patterns and compared with state-of-the-art techniques. • A stereo visible-thermal calibration procedure for multi-modal vision system. • A novel feature extraction pipeline that mitigates the contrast inversion and is robust to specular reflections. • An iterative optimization procedure that helps the detection of the thermal pattern. • An optimized use of low-cost and easy-to-build calibration targets for the visible-thermal range. [ABSTRACT FROM AUTHOR]

• Proposed an adaptive exposure adjustment algorithm, eliminating the need for manual intervention during the calibration process, making the calibration process more robust to environmental changes. • Proposed an adaptive blur adjustment algorithm, enhancing the clarity of calibration images, addressing the issue of uncontrollable blurring in previous algorithms, and improving the accuracy of camera intrinsic parameter calibration. • Designed a semi-automatic high-precision calibration strategy that addresses significant discrepancies in calibration results obtained from different calibration processes in traditional algorithms, thus improving robustness. Camera calibration is a prerequisite for many computer vision tasks, such as visual measurement and visual localization. This paper proposes a new method for high-precision calibration of camera intrinsic parameters. By dynamically adjusting image brightness and blur to cope with changes in external lighting conditions and camera working distance, high-precision internal parameter measurement is achieved. This method solves the problems of the traditional camera intrinsic parameter calibration process being cumbersome and susceptible to changes in the placement of calibration boards and fluctuations in external lighting conditions. Firstly, an adaptive exposure adjustment algorithm is proposed to adjust the camera exposure value by statistically analyzing the average gray value of randomly selected rectangular regions on the calibration board, thereby solving the problem of the camera calibration accuracy being affected by overly bright or dark environments. Subsequently, an evaluation criterion and adaptive adjustment strategy for adjusting image blur are proposed. By extracting edge points of feature circles and obtaining the slope of the fitted curve, the relationship between edge sharpness and slope is utilized to adjust the image blur. Finally, the proposed method achieves high-precision semi-automatic calibration. Experimental results demonstrate that the proposed method has significant advantages in terms of correctness, robustness, and flexibility, with an average reprojection error of 0.0167. [ABSTRACT FROM AUTHOR]

A real-time calibration to enhance the inter-subject reproducibility of insulin bioavailability measurements was proposed and validated on a diabetic patient with more than 49000 impedance values. The measurement method monitors drug absorption through a transducer consisting of a sensitive material (human abdominal tissue) and an impedance spectrometer. The in-vivo experiments revealed a statistically significant negative second-order polynomial trend in impedance magnitude corresponding to the amount of rapid-acting insulin injected. To manage the uncertainty inherent in the sensing block, the method integrates real-time calibration. Implementing a real-time calibration method based on a customized model identification at each insulin administration resulted in a reduction in deterministic error by a factor of 18. A further reduction in deterministic error for clinical application (46%) was achieved with a customized parameter second-order polynomial model with respect to the customized parameter linear model. Lastly, when less conductive long-acting insulin was administered, an increasing trend in impedance magnitude was observed, aligned with the theoretical framework of the proposed method. • A non-invasive real-time and low-cost method measures insulin bioavailability. • A customized model of insulin uptake is identified based on daily physiological conditions of patient. • The method was validated by acquiring more than 49000 impedance values on a diabetic patient. [ABSTRACT FROM AUTHOR]

The accurate measurement and control of blackbody temperature can play an important role in radiometric calibration. A novel circuit suitable for the aerospace environment is designed to measure and control the temperature of the blackbody. A coarse-fine measurement method considering the wire resistance and self-heating effect of the platinum resistance is presented to calculate the resistance values of the platinum resistors. The precision of temperature measurement is improved using a line fitting algorithm with error calibration and temperature drift error compensation. A fuzzy self-adaptive PID controller is designed to improve the temperature control effect. The performances of the developed system are implemented on an FPGA/A3PE3000-FG484I controller board. The test results show that the device temperature measurement precision can reach ± 0. 03 K for the entire temperature range 238 K to 367 K , the temperature stability is better than 0.02 K /20 s , and the temperature uniformity is better than 0.1 K. • A temperature measurement and control circuit suitable for the aerospace environment is designed. • A coarse-fine measurement method considering the wire resistance and the self-heating effect of the platinum resistance is presented to calculate the resistance value. • The temperature measurement precision is improved using a line fitting algorithm with error calibration and temperature drift error compensation. • The test results show that the temperature measurement precision can reach ±0.03 K, the stability and uniformity of the temperature are better than 0.02 K/20 s and 0.1 K, respectively. [ABSTRACT FROM AUTHOR]

• The proposed decoupling model fully takes into account the effects of unexpected frame deformations and inertia loads on the measurement results of the Rotational Multi-axis Force Sensor (RMFS), and is deduced via an Extreme Case-Compare Method. • A two-step calibration approach is proposed to determine the unknown coefficients of the centralized load decoupling model, whose feasibility is numerically and physically validated. • The accuracy and anti-vibration capability of the RMFS are improved by the proposed decoupling model, which is demonstrated through physical experiments. For ensuring the safe mobility of off-road wheeled mobile robots (WMRs), the rotational multi-axis force sensor (RMFS) plays an important role in measuring the wheel-terrain interaction forces. However, the existing decoupling models cannot fully describe the coupling process of the RMFS when it is subjected to centralized loads, which is a common condition for off-road WMRs. A corrected decoupling model is proposed by taking elastic strains as the intermediate variable such that the coupling errors caused by centralized loads can be avoided. The proposed decoupling model replaces the original rotation matrix with a corrected matrix whose elements are odd harmonic functions. The calibration experiments indicate that the corrected model can reduce the variance of calibration error rate from 1.95% to 0.054% compared with another representative machine learning-based decoupling model. A set of simulation and physical tests also demonstrate that the decoupling model have good repeatability, accuracy and anti-vibration capability. [ABSTRACT FROM AUTHOR]

• Design a new mirror-image stereo target composed of a planar target and a plane mirror. • Propose a global calibration method for vision measurement system. • Study three nonlinear optimization algorithms to improve the precision of coordinate system transformation. • Simulation and experiments verify the feasibility of MST and the accuracy of the global calibration algorithm. Using three-dimensional (3D) targets to solve the transformation relationship between the local and global coordinate systems is a common global calibration method. However, 3D targets have complex structures and high costs. And multiple coordinate transformations during global calibration can cause significant cumulative errors. Therefore, based on reflection imaging, this paper designs a new mirror-image stereo target (MST) and analyzes its view area and three structural parameter constraints. A new global calibration method is proposed, as well as three optimization algorithms for pose solution between MST, optical 3D sensor and global camera to improve the global calibration accuracy. The experimental results show that the registration errors of two workpieces are 0.086 mm and 0.114 mm, respectively, confirming the feasibility and precision of the proposed method. Our method is flexible, requiring only a planar target and a mirror, rather than complex 3D targets, to achieve global calibration with non-overlapping field of view. [ABSTRACT FROM AUTHOR]

• Present a novel DCC potentiometer. • Present a data-driven multi-channel information fusion method for DCC potentiometer measurement. • The proposed data fusion method has been validated experimentally. • The DCC potentiometer is characterized as high-precision. • Providing a novel view for developing high-precision rotary position sensor. The main objective of this work is to develop a novel Dual-Channel Complementary (DCC) potentiometer to enhance the measurement accuracy of the conventional rotational potentiometer. Its principle is utilizing the complementary characteristic of the signals, which exist a specific phase offset, from different channels to reduce the effect of their inherent nonlinearity on measurement accuracy, and increase the measurement accuracy. A data-driven multi-channel information fusion method has been proposed to fuse the signals of the Dual-Channel Complementary (DCC) potentiometer, which could achieve data fusion and sensor nonlinearity calibration in one go. Prototype has been developed to evaluate the efficiency of the proposed DCC principle and information fusion method. Experimental results reveal that compared to the conventional rotational potentiometer, the RMS value of the measurement error of the DCC potentiometer could achieve a reduction of about 99.5%. The overall measurement performance of the DCC potentiometer could be significantly enhanced. [ABSTRACT FROM AUTHOR]

• Low-cost measurement platform for particulate matter monitoring developed. • Artificial intelligence field calibration procedure of low-cost sensor proposed. • Combination of affine scaling and optimized neural network surrogate employed. • Correlation coefficient improved to 0.86 for particulate matter of size 1 μm. • Root-mean-squared error of 3 μm/m3 (1 μm particles) and 4.9 μm/m3 (10 μm particles) Due to detrimental effects of atmospheric particulate matter (PM), its accurate monitoring is of paramount importance, especially in densely populated urban areas. However, precise measurement of PM levels requires expensive and sophisticated equipment. Although low-cost alternatives are gaining popularity, their reliability is questionable, attributed to sensitivity to environmental conditions, inherent instability, and manufacturing imperfections. The objectives of this paper include (i) introduction of an innovative approach to field calibration for low-cost PM sensors using artificial intelligence methods, (ii) implementation of the calibration procedure involving optimized artificial neural network (ANN) and combined multiplicative and additive correction of the low-cost sensor readings, (iii) demonstrating the efficacy of the presented technique using a custom-designed portable PM monitoring platform and reference data acquired from public measurement stations. The results obtained through comprehensive experiments conducted using the aforementioned low-cost sensor and reference data demonstrate remarkable accuracy for the calibrated sensor, with correlation coefficients of 0.86 for PM 1 and PM 2.5 , and 0.76 PM 10 (particles categorized as having diameter equal to or less than 1 μm, 2.5 μm, and 10 μm, respectively), along with low RMSE values of only 3.1, 4.1, and 4.9 µg/m3. [ABSTRACT FROM AUTHOR]

• A cylinder instead of sphere is used for calibration, which is easy to manufacture and can cover a larger robot workspace. • An unconstrained dimensionality reduction method is proposed to accurately fit the incomplete conic profiles as ellipses. • The calibration error of hand eye parameters is reduced by about 50% compared to feature points col-linearity based method. This paper proposed a hand-eye calibration method for a line structured-light (LSL) scanner mounted on industrial robot. Unlike widely used spherical targets, the target used in our work is a cylinder, which is inexpensive and easy to be manufactured in larger size to cover a wider calibration space. In order to address the profile self-occlusion and drastically shape changing of conic section during calibration, an unconstrained dimensionality reduction method is proposed to fit the scanned profiles. Based on fitted ellipse centers under various robot poses, the hand-eye calibration model is developed based on the difference between cylinder radius and the distance from the profile point to the cylinder axis. Simulation and actual experiments have shown that the proposed ellipse fitting method is more accurate and robust, and the calibration method achieves higher reconstruction accuracy under the same robot positioning error, need less robot operations to obtain more accurate hand-eye parameters. [ABSTRACT FROM AUTHOR]

• Adaptive calibration in fault localization enhanced by semantic segmentation. • Precise fault localization with multiscale analysis at macro and micro levels. • Approach validated through extensive simulations and field tests for accuracy. • An industrial prototype demonstrating the superiority of our approach over existing methods. Fault localization is crucial for ensuring stability, particularly in high impedance faults (HIF) characterized by low current levels and prolonged transient processes (TP). Existing methods predominantly analyze differences in the fixed-length transient waveform, potentially causing delays in triggering or failure in HIF scenarios. To address these challenges, a novel AI application paradigm for HIF localization was introduced, incorporating both adaptive TP calibration and multiscale correlation analysis. Based on 1D-Unet, the TP of the zero-sequence voltage (ZSV) can be adaptively calibrated to maximize the utilization of transient information. Subsequently, the differential zero-sequence voltage (DZSV) and transient zero-sequence current (TZSC) can be acquired to facilitate multiscale correlation analysis. Combined with a sliding window strategy, the micro correlation between DZSV and TZSC is articulated through the local correlation degree (LCD). The comprehensive correlation degree (CCD) between DZSV and TZSC is then formulated to realize fault feeder/ section localization at the macro level. The 1D-Unet model achieved a classification accuracy of 99.2 % for sample points in test datasets and showed robustness with an accuracy exceeding 93.5 % in the presence of 20 dB noise interference. When integrated with the well-trained 1D-Unet, the proposed approach underwent further validation using simulation data and field recordings. These tests confirmed the model's resilience to noise interference up to 20 dB and its efficacy across networks of diverse topologies, such as the IEEE-13 and 34-node distribution networks. Additionally, an industrial prototype applying this framework identified all fault conditions without false positives or omissions, outperforming existing methods under various fault scenarios, including those involving high impedance materials and different resistance levels across multiple feeders. [ABSTRACT FROM AUTHOR]

• Multiple stereo-based high accurate 3D measurement of ship block is proposed. • A more accurate two-step calibration algorithm is proposed. • The 3D accuracy of proposed method was validated by actual ship block measurement. A multiple stereo-based three-dimensional (3D) measurement method of large-scale structures is presented, which replaces time-consuming and laborious 3D measurement procedure of laser-based conventional equipment. To have 3D reconstruction accuracy with millimeter-precision, two-step calibration algorithms are improved. Specifically, we use 2D epipolar constraint, using fundamental matrix determined by matched points, to new combination of objective function for intrinsic parameter calibration. We additionally propose an onsite structure parameter calibration algorithm using different epipolar constraint of measurement points in images of large ship block as well as reprojection error of checkerboard, to bypass the limitation of the coverage of checkerboard in large-scale measurement. The actual 3D measurement of the three ship blocks is conducted, and the 3D reconstruction accuracy is validated by comparing the 3D coordinates measured by total station. The experimental results showed that the mean 3D reconstruction error ranged from 6 to 14 mm. [ABSTRACT FROM AUTHOR]

• A thrust vector control test system with four-point support dynamometer is proposed. • The deflection flange structure is used to realize the large loading of vector force. • Three-way static calibration test of dynamometer was carried out on the test system. • Nonlinear/repeatability error and interphase interference all meet test requirements. The accurate measurement of thrust vector is very important to improve the life and safety of aircraft engine. In order to meet the requirements of thrust vector test of a solid rocket engine and overcome the contradiction between large thrust (>50 kN) and high-frequency response (≫30 Hz)/high precision measurement (<3%), a thrust vector control test system utilizing a four-point support piezoelectric dynamometer (FSPD) and a deflected flange structure was proposed. The test system mainly consists of a four-point support piezoelectric dynamometer and some vector force simulation loading devices. The theoretical mechanical model and the thrust vector control test system was set up to study the performance of solid rocket engine. Firstly, the piezoelectric elements and four-point support piezoelectric dynamometer were calibrated by the three-direction force calibration loading device. Secondly, the rationality and feasibility of the thrust vector control test system were proved by the simulated loading experiment. The research results show that the static and dynamic performance of the test system meet the test requirements, and it has good linearity and repeatability, errors are less than 1.00 %, and interphase interference is less than 2.00 %. The measuring system proposed in this paper provides a new idea for the accurate measurement of vector force with large load and high-frequency response. [ABSTRACT FROM AUTHOR]

• To solve the difficulty of 3D curved surface defect detection, a 3D curved optical surface defect detection method based on micro structured-light detection is proposed and a complete detection setup is built. • The method can achieve a detection accuracy comparable to that of the white light interferometer, and at the same time, the FOV is larger and the environmental requirement is lower. • A multi-parameter calibration method is proposed to realize the camera calibration based on the telecentric optical path and the geometric calibration of the MSLD system. To solve the difficulty of 3D curved surface defect detection, a 3D curved optical surface defect detection method based on micro structured-light detection (MSLD) with large field of view (FOV) is proposed to detect typical defects such as scratches and digs. And a multi-parameter calibration method for MSLD is proposed, which does not have strict requirements on the placement of the camera and the screen and can effectively correct the distortion. Simulations verify the feasibility of the proposed method. 3D detection of different types of weak defects on convex and concave surfaces is also performed. The experimental results show that the reprojection error after calibration is less than sub-pixel, and also show that MSLD can achieve comparable accuracy to white light interferometry (WLI). The difference in measured defect depth between MSLD and WLI is less than 0.5 nm, and the difference in measured defect width is less than 1 μm. [ABSTRACT FROM AUTHOR]

• A novel robot hand-eye calibration method is proposed without complicated error identification. • Robot hand-eye can be effectively calibrated without calculating the complex matrix equations. • Robot relocalization is implemented to reduce the introduction of robot kinematic error. • The IRLS spherical fitting algorithm is used to suppress the influence of measurement noise. • The error of the proposed method in the criterion sphere splicing verification is only 0.0323 mm. The accuracy of hand-eye calibration is easily affected by robot kinematic error, measurement error, random error, etc., and can be to a certain extent enhanced by the complicated error identification. To address this problem, we propose a novel errors-unidentified hand-eye calibration method. A relocalization-based hand-eye calibration is implemented to overcome the challenge from robot kinematics at first owing to the high robot relocalization accuracy. The tool center point (TCP) coordinates are then obtained based on an iterative reweighted least squares (IRLS) spherical fitting algorithm. An iterative combinatorial refinement algorithm is finally presented to search the solutions in the form of permutation and combination when solving the rigid transformation matrix. Experiments on criterion sphere and blade demonstrate that by converting the hand-eye matrix solving problem into a point set matching problem, the accuracy of the proposed method is enhanced by 60% on average compared with three state-of-the-art hand-eye calibration methods. [ABSTRACT FROM AUTHOR]

• A novel backpropagation neural network-based calibration method is proposed for accurate weight coefficient estimation of multi-camera light field PIV. • The principle and implementation of the proposed method are described. • Synthetic tests of a ring vortex field and experiments on a low-swirl injector flow are conducted to evaluate the proposed method. • A comparative study is conducted with the conventional direct ray tracing method. • The potential applications and challenges of the proposed method are outlined. Volumetric velocity measurement through multi-camera light field particle image velocimetry (LF-PIV) requires an accurate estimation of the weight coefficient (WC) of three-dimensional (3D) tracer particle distribution reconstruction. To achieve that, this study proposes a calibration method based on a backpropagation neural network (BP-NN) for the WC estimation of the multi-camera LF-PIV. The BP-NN model establishes a mapping relationship between the spatial voxels and pixels of the multi-cameras. The proposed method is compared with the direct ray tracing (DRT) method and it shows that the proposed method provides an accurate estimation of the WC. It also does not depend on the prior knowledge of angle separations of the multi-cameras as is required for the DRT method. The proposed method is initially evaluated by conducting synthetic tests of ring vortex field reconstruction and further verified by conducting experiments on a low-swirl injector (LSI) flow. Results show that the root mean square error of the ring vortex displacement field can be reduced from 0.71 voxels to 0.35 voxels by the proposed method. The relative errors of LSI flow axial and radial velocity components are smaller than 10%. Therefore, it demonstrates that the 3D flow velocity can be measured accurately by the multi-camera LF-PIV by incorporating the proposed BP-NN calibration method. [ABSTRACT FROM AUTHOR]

The accuracy of underwater navigation is significantly impacted by the scale factor error and misalignment angle of the Doppler Velocity Log (DVL). A DVL calibration method based on position observation information is proposed as a solution to the integrated navigation system composed of compass, DVL, ultra-short baseline acoustic positioning system, and depth sensor. A transfer model from DVL error parameters to the positioning error of Dead Reckoning (DR) is established. Based on this model, dual-loop Kalman filter (KF)-based and particle swarm optimization (PSO)-based DVL error parameter estimation algorithms are proposed. Compared with classical methods, the proposed methods achieve high-precision DVL calibration in deep-water environments at a lower cost. Simulation and sea trials show that both proposed algorithms exhibit excellent stability, consistency, and accuracy. After calibration, the positioning errors of DR have decreased from 1.56% to 0.28% and 0.23% of the voyage, respectively. [Display omitted] • DVL calibration methods with position observation have higher calibration accuracy. • Error transfer model of DVL enables its calibration using position observation info. • The KF-based DVL calibration method has advantages in real-time performance. • The PSO-based DVL calibration method provides higher calibration accuracy. [ABSTRACT FROM AUTHOR]

[Display omitted] • Equivalence between continuous- and discrete-time models of optical flow sensor. • Optical flow sensor's calibration method via in-situ rotation. • Unmanned aerial vehicle position estimation algorithm based on optical flow sensor. To better reveal the principle of off-the-shelf OFS that used for UAV position estimation, two measurement models are derived, namely the continuous-time and discrete-time models. Then the intrinsic equivalence of these two models is also proven. Based on these two models, a calibration method for OFS is introduced, which only makes use of in-situ rotation to determine the OFS's parameters including its focal length and installation angles with respect to the UAV. Furthermore, an OFS-based UAV position estimation algorithm is presented, which stems from the proposed discrete-time model. The proposed OFS models, calibration method, and position estimation algorithm form a full solution for UAV displacement measurement via OFS, and its feasibility and effectiveness is verified through flight tests on a quadcopter UAV in outdoor environment. [ABSTRACT FROM AUTHOR]

• GI-SAXS for pitch calibration with traceability to SI was developed. • Statistically significant systematic errors was found on pitch calibrations. • The origin of the systematic errors was identified. Grazing-incidence small-angle X-ray scattering (GI-SAXS) is a promising technique for investigating nanostructured surfaces, particularly for the fine pitch calibration of one-dimensional gratings. However, only a few studies validated this technique from a metrological perspective. In this study, we developed a GI-SAXS system traceable to length and angle standards and used it to analyze the uncertainty of pitch calibrations in detail. Consequently, we found statistically significant systematic errors which have not been reported so far. We also found that the systematic error varied depending on the signal width of the diffracted X-rays. Through theoretical modeling and quantitative experiments, we successfully explained that the source of the systematic error is intensity modulation along the grating truncation rod. Since the systematic error decreases with smaller signal width, optimizing the optical system may efficiently reduce the uncertainty. [ABSTRACT FROM AUTHOR]

• User-conducted calibration methods are the easiest among the various calibration methods for consumer-grade MEMS-IMUs. • User-conducted calibration methods are doable by an end-user without complex equipment or support. • Pertinent literature collected systematically from popular digital libraries (published between 2000 and 2023). • The review paper classifies and analyzes popular IMU user-conducted calibration methods, listing their features. MEMS-IMUs 1 1 MEMS-IMU- Microelectromechanical systems based inertial measurement unit. are cost-effective, self-contained, small-size, low-power devices used in various motion tracking and sensing applications. The triaxial gyroscope and accelerometer in a typical 6-axis IMU measure the angular rate and specific force that can be used directly or fused using sophisticated algorithms to estimate position, velocity, and orientation (pose) information. Despite their advantages, MEMS-based IMUs are highly noisy, containing systematic and stochastic errors. Though stochastic noises can be characterized and minimized with various analysis methods and algorithms, systematic errors need to be identified and removed with a suitable calibration process. Among the various calibration methods, the easiest methods for consumer-grade-IMU are user-conducted methods, doable by an end-user without complex equipment use or support. This paper reviews, classifies, and analyzes popular user-conducted calibration methods for MEMS IMUs and lists their features and standard mathematical models based on the literature (published during 2000–2023) systematically collected from popular digital libraries. [ABSTRACT FROM AUTHOR]

[Display omitted] • Partial discharge calibration in gas-insulated substations. • Directional coupler for partial discharges in gas-insulated substations. • Electric and magnetic couplers interaction. • Partial discharge reflectometry in gas-insulated substations. This paper introduces a directional coupler for partial discharge (PD) measurements in gas-insulated substations (GIS). The sensor comprises a combination of magnetic and electric couplers, effectively segregating forward and backward pulses to enhance PD charge estimation and defect location. The sensor's design was supported with finite element method simulations and measurements conducted in a transverse electromagnetic test bench. Comparative analyses were performed against independent magnetic and electric couplers. The charge estimation and the directional coupler's directivity were evaluated in both the test bench and a full-scale GIS with different PD defects. Initially, the combined magnetic and the electric couplers exhibited undesired interactions, prompting corrective measures. Subsequent adjustments included changes to the electric coupler material and modifications to the magnetic coupler construction. The resulting high-voltage directional coupler performed better than the separated couplers in a GIS with discontinuities. This partial discharge sensor emerges as a candidate for future SF 6 -free alternative GIS. [ABSTRACT FROM AUTHOR]

• Nanoindentation is a thorough and flexible mechanical quality tests. • A metrological framework to benchmark testing equipment performances is missing. • A methodology is proposed propagating reproducibility and calibration traceability. • Nonparametric simulative approaches are needed to evaluate calibration uncertainty. • The methodology is applied on applications with various environment and platforms. Instrumented Indentation Test (IIT) is a nonconventional mechanical tests allowing multi-scale mechanical characterisation. It is employed for research and quality control in strategic manufacturing fields for developing edge technologies. The state-of-the-art lacks a robust methodology to assess quality of indentations and benchmark indentation devices. This is limiting the application of IIT for specifying and verifying tolerances. This work proposes an uncertainty-based quality evaluation tool for IIT. A non-parametric uncertainty evaluation of calibration contribution is proposed. The method shows the statistical significance of indentation sets modelled by the bootstrap samples. The uncertainty is then propagated according to the law of uncertainty propagation for the evaluation of mechanical characteristics. The methodology is applied to five case studies. Results show that the uncertainty evaluation model can achieve robust and sensitive quantification of the indentation results and system quality, thus providing a useful practical tool for industrial and academic practitioners within a metrological framework. [ABSTRACT FROM AUTHOR]

In this study, an infrared system is developed for accurate measurements of surface temperature and heat transfer on fast moving targets. The system was designed for the Oxford Turbine Research Facility, a world-leading experimental facility delivering highly engine representative, scalable heat transfer results for aerospace research. Infrared thermography is employed to acquire temperature maps of high-pressure turbine blades, allowing assessment of surface thermal conditions including heat transfer coefficient, adiabatic wall temperature, Nusselt number, cooling effectiveness, and metal effectiveness. Achieving accurate infrared thermography measurements in rotating turbomachinery experimental conditions is arduous due to reflections from the surroundings, low emissivity of metallic parts, and motion blur resulting from high speed. To overcome these challenges, calibration procedures were developed against a traceable standard using a bespoke steady experimental facility. A method to determine the reflected temperature from surroundings was also validated. Correction for all measurement disturbances is demonstrated to within the accuracy of the primary measurement thermocouple. Finally, the developed calibration method was validated on a fast-moving rotating geometry demonstrating accurate correction for all measurement disturbances, without the need for an in situ calibration. A detailed uncertainty analysis for each calibration step is also presented. • Limitations in infrared thermography techniques in challenging environments. • Novel calibration methods to enhance IR thermography measurement accuracy. • Impact of target motion and blur on infrared emissivity and reflection calibrations. • Improved accuracy of infrared measurement for metal effectiveness and heat transfer. [ABSTRACT FROM AUTHOR]

• Earth pressure cell (EPC) calibration factor varies with contact material. • EPC response is affected by contact material's stress-strain behaviour. • Calibration factor variation triples with sand and geofoam compared with fluid. • Calibration response becomes non-linear with compressible materials. The earth pressure cells (EPC) response is highly dependent on the contacting material which is not always a soil, as several other materials are also used in geotechnical engineering. In the present study, 30 nos. of EPCs are calibrated with river sand and geofoam (EPS15) as contacting materials, as these EPCs are being used in the field to investigate suitability of the geofoam inclusion. The variability of individual EPCs with different contacting materials is determined by calculating the coefficient of variation (COV) of the calibration factor. The COV for manufacturer's calibration factor is 2.61%, which increases significantly to 8.22% for river sand and 7.14% for EPS15 as contacting materials, demonstrating the importance of EPC's proper calibration for reliable measurement of earth pressures. The EPC calibration factor determined in the present study is significantly different from that provided by the manufacturer, which invariably bring significant error in pressure measurement with these EPCs. [ABSTRACT FROM AUTHOR]

• Correction matrix error ignored in the error model causes significant azimuth errors. • EABC algorithm effectively reduces system errors, including Correction matrix errors. • EABC method avoids complex iterative calculations, ensuring real-time performance. The precision of azimuth calculation in measurement-while-drilling systems is heavily reliant on the triaxial magnetometer, necessitating proper calibration to minimize azimuth errors. To address the need for high-precision calibration of systematic errors such as sensor scale factors, bias, and non-orthogonality, a relationship between the error model and the correction matrix is derived and a novel equal angle balance correction method to calibrate azimuth is proposed. Experimental results demonstrate that the mean azimuth error generated by this algorithm is less than 0.00624°, which is at least 28 times lower than that of the ellipsoid fitting correction method. The algorithm effectively eliminates systematic errors and meets the practical engineering requirements for azimuth calibration in measurement-while-drilling systems. [ABSTRACT FROM AUTHOR]

• Determining load cell parameters using a new method which is the long-term creep. • Difference is observed between parameters measured using creep and dynamic methods. • Adapters and rocking modes could affect parameters' accuracy obtained in dynamic mode. • The expanded uncertainty in the creep is lower than that determined in dynamic mode. Many mechanical systems in industry need dynamic force calibration for accurate measurements. This is due to the sensitivity of load cells changed greatly after their natural frequencies. Load cell parameters are used in predicting sensitivity and the frequency range where this cell can be used. These parameters values are constants depending on the load cell's material and structural design. Consequently, they can be obtained under exerting static, or dynamic force. The aim of this paper is to demonstrate a new study for measuring the load cell parameters accurately under applying long-term creep test. Then, these parameters are compared to those measured while exerting dynamic force of sine mode. A clear difference has been observed between the two measurement methods. Rocking modes, and adapters in the dynamic measurement method affect the parameters accuracy. Generally, static measurement methods are well defined than dynamic in force application and deflection measurement, and less complex. [ABSTRACT FROM AUTHOR]

• A data fusion control-based broad-band and high-dynamic excitation generation method used for improving the vibration calibration performance is proposed. • Several amplitude attenuation, phase lag, and noise resistance simulations compared with the traditional PID-based method are accomplished. • The SNR, dynamic range, and accuracy improvement comparison experiments with the conventional methods were achieved. The low-frequency vibration sensors are widely used for monitoring vibration in various engineering, and their sensitivity must be calibrated in order to ensure monitoring performance. Currently, the linear shaker is usually applied to provide an excitation for calibrating the sensors. However, this calibration process has the disadvantages of narrow low-frequency range, low signal-to-noise ratio (SNR), and high total harmonic distortion, which severely limits the improvement of calibration ability. In this study, a data fusion control-based broad-band and high-dynamic excitation generation method was proposed, which provides the linear excitation with broad-band high-dynamic for the sensors to achieve high-performance calibration. The simulations demonstrate that the amplitude attenuation and noises can be effectively eliminated in the range of DC (quasi-static)-150 Hz. The comparison experiments with the shaker show that the proposed method has the ability to generate high-dynamic and low-distortion excitation acceleration in 0.01–5 Hz and improve the SNR 40 dB of the excitation. Moreover, the low SNR of the sensor output signal is also well suppressed. [ABSTRACT FROM AUTHOR]

• An accurate and robust calibration method is established for simultaneous Stokes polarimetry. • Appropriate calibration polarization states and light intensity monitoring can enhance the accuracy and robustness of polarization calibration. • The maximum root-mean-square error of the measured Stokes vector can be minimized to less than 0.0061. The simultaneous Stokes polarimetry (SSP) plays a crucial role in various fields, including the characterization of suspended particles in air and water, as well as the measurement of the Mueller matrix of samples. System calibration is a critical step for improving the accuracy of the Stokes polarimetry. However, there is a lack of commercially available SSP, and the corresponding calibration method is not yet fully developed. In this paper, an accurate and robust calibration method for SSP based on division-of-amplitude is proposed, which includes intensity monitoring and geometric optimization. The optimal calibration method significantly can reduce measurement time while maintaining high calibration accuracy and robustness. The maximum root-mean-square error of the measured Stokes vector can be minimized to less than 0.0061, which represents approximately a tenfold improvement in accuracy compared to the traditional calibration method using a rotating quarter-wave plate. Additionally, the measurement errors of Stokes vectors are minimized globally to ensure robust measurement. Based on this foundation, the calibrated SSP is capable of tracking the changes in random Stokes vectors with fast speed. These results demonstrate the importance of selecting appropriate calibration polarization states and the significance of incorporating light intensity monitoring to enhance the accuracy and robustness of polarization calibration. [ABSTRACT FROM AUTHOR]

• Accurately measuring high concentration particle concentration while preventing contamination. • Establishing a functional relationship to describe changes in powder contamination using a fiber optic probe. • Combining microscopic particle contamination patterns with macroscopic particle extinction measurements. Achieving real-time measurements of ultra-fine dry chemical agents (UDCA) is extremely challenging, with their complex composition, high injection concentrations, and susceptibility to contamination. In this study, a high-concentration particulate matter measurement method was proposed based on the extinction principle to reduce the powder contamination effect during calibrations. Through theoretical analysis and experimental verification, a functional relationship was established. Calibration experiments were conducted using sodium bicarbonate (SBA) and potassium bicarbonate (PBA) UDCAs, which are the most representative. The results showed that the measurement ranges of SBA and PBA reached 227.15 g/m3 and 122.55 g/m3, respectively. Compared with the uncorrected calibration method, the maximum indicated errors of SBA and PBA with the powder contamination effect corrected were reduced from 11.25% and 22.68% to 5.98% and 9.21%. This method provides a strategy for measuring high concentration powder, especially for achieving the measurement of UDCA in aircraft engine compartments. [ABSTRACT FROM AUTHOR]

Current comparator bridges are employed for the realization of the resistance scale from the quantum Hall effect in several National Metrology Institutes and calibration centers. Quantum resistance standards under development, based on novel materials and tabletop dry cryostats, make the more achievable DC current comparator bridges (DCCs) a viable alternative to the more accurate but more expensive cryogenic current comparator bridges (CCCs). A DCC ratios' calibration against a reference CCC is a straightforward way to improve the DCC's performances and the resistance scale overall accuracy. The paper reports the calibration results of two DCCs on the ratios employed in a 1 Ω to 10 k Ω resistance scale traceable to a 12. 906 k Ω quantized Hall resistance, showing a good reproducibility and stability of the DCC readings over the measurement period and supporting the possibility of a DCC errors' correction and of a realization of the primary resistance scale at the 10-8 level. • Calibration procedure of DC resistance ratio bridges is provided. • Ratio errors of DC resistance ratio bridges are determined by comparison with a cryogenic current comparator. • Reproducibility of the ratio error of DC resistance ratio bridges over time is confirmed. • Uncertainty of correlated time series is expressed. • Realization of a resistance scale from the quantum Hall effect. [ABSTRACT FROM AUTHOR]

In this paper we show that velocity indication of vane anemometers with a propeller placed at the end of a mounting rod installed perpendicularly to air flow can vary by several percent (up to 9% in our tests) if the length of the mounting rod exposed to flow (insertion depth) is changed. Four vane anemometers of different dimensions were tested for velocities (2–20) m/s and for the insertion depths (7.5–37.5) cm. Interlaboratory comparison was conducted showing how the effect influences the calibration results in five different wind tunnels with test section diameters/widths from 25.5 cm to 100 cm. Important conclusions were drawn for air speed calibration laboratories whose uncertainties are usually an order of magnitude smaller than the variations of the measurement error observed for some of the anemometers. Also, it was shown that the effect can be nearly eliminated by changing the cross-sectional profile of the mounting rod from circle to an airfoil. • Insertion depth dependencies of reading of vane anemometers are investigated. • Measurement error variations significant for calibration practice are found. • Airfoil cross-sectional profile of a mounting rod nearly eliminates the effect. • Intercomparison of wind tunnels with different test section dimensions is conducted. • Important conclusions for air speed calibration laboratories are drawn. [ABSTRACT FROM AUTHOR]

[Display omitted] • An automated measurement method is proposed using the R-test device, which improves measurement accuracy and efficiency. • A hybrid adaptive identification algorithm is proposed, which has high identification speed and robustness. • A high calibration accuracy is ensured across the entire workspace, even after tool replacement. • The proposed method is verified by simulations and experiments. Kinematic calibration is an effective method for ensuring the accuracy of hybrid machine tools. Traditional calibration methods are limited by cumbersome operations and poor algorithm robustness. In this study, measurement methods and identification algorithms are studied, and a new calibration method is proposed. First, the configuration of the hybrid machine tool is described, and an error model is constructed. Then, an automated measurement method of tool center point position error for multiple test arbors is proposed using the R-test device. Subsequently, a hybrid adaptive identification algorithm is proposed by sequentially solving the unit inhomogeneity of the identification model, the rank deficiency produced by incomplete measurements, and the multicollinearity between error parameters. Finally, the efficacy of the proposed calibration method is verified through simulations and experiments. The proposed method significantly improves the calibration efficiency and accuracy and proposes a new solution for automated calibration. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new 3D microscope is designed by combining telecentric imaging and multi-angle Scheimpflug projection. • The improved and practical joint calibration method realizes high-accuracy system calibration. • The point-cloud registration error correction model achieves complete and high-precision microscopic 3D measurement. • A simple and effective approach is provided for 3D measurement of complex micro-structures. 3D measurement of complex micro-structures has becoming increasingly important for precision manufacturing. In this paper, a multi-angle Scheimpflug projection 3D microscope (MASP-3DM) is proposed, and the detailed design procedure is given. The system deployed four Scheimpflug projections and one telecentric imaging to overcome the shortcomings of limited depth of field (DOF), occlusion and reflection. Then, an improved and practical system calibration method is proposed, which utilizes pinhole projection model to calibrate the telecentric imaging. Meanwhile, local homography is combined with perspective-n-point (PnP) strategy to improve the calibration accuracy. Further, a point-cloud registration error correction model is established to achieve complete and high-precision measurement. The experimental results indicate that the re-projection error is within ±0.5μm and the registration error is less than 2μm for system calibration, the maximum of mean deviation, measurement bias, standard deviation, and type A uncertainty are respectively less than 3μm, 7μm, 4μm, and 1μm for 3D measurement, within the 10(H) mm ×50(W) mm ×40(D) mm volume. [ABSTRACT FROM AUTHOR]

• A calibration-less deconvolution method is proposed to retrieve multi-peak space-charge distributions. • Reconstruction of simulated charge distributions proves the accuracy of the method even when closely spaced peaks exist. • Experimental results show the proposed method outperforms the conventional method in reconstructing charge profiles. • The proposed method offers a simple, fast, and accurate alternative to conventional deconvolution methods. The electrical and mechanical properties of a dielectric material are significantly influenced by its charge distribution, necessitating an understanding of how charge accumulation occurs in order to determine the suitability of use for specific applications. This research presents a novel approach to deconvolving charge distributions with multiple peaks while dispensing with calibration measurement required by the non-contact pulsed electro-acoustic technique. Unlike traditional deconvolution methods that rely on reference signal measurements, the proposed approach reconstructs the charge distribution through parameters directly estimated from the piezoelectric transducer output voltage, effectively eliminating the need for such measurements altogether. Simulations show that even when closely spaced peaks exist within multi-peak charge distributions, our method can accurately reconstruct their profiles. In addition, the charge distributions obtained from experimental data of PTFE, FEP, and PEEK indicate that the proposed approach outperforms traditional methods in predicting penetration depth while reducing fluctuations and spurious peaks. We expect this method to be a valuable tool for the design and optimization of electronic systems in harsh environments through offering a simple, fast, and accurate alternative to conventional deconvolution methods. [ABSTRACT FROM AUTHOR]

In contrast to conventional methods of optimizing feature-matching results at the data-processing level, we utilize the tightly coupled mode to fuse the information collected by the camera and inertial sensor at the data-gathering level, which contributed to better accuracy and robustness in the feature-matching process. Specifically, the proposed visual-inertial feature tracking method that combines inertial measurement unit (IMU) calibration, feature matching, and prediction algorithms. The approach includes a vision-aided multi-level IMU systemic calibration method and an inertial-aided image feature prediction algorithm, which effectively processes and utilizes information from multiple sensors. Our method addresses not only the influence of image distortion and blur resulting from illumination changes and fast camera motion but also the problem of measurement errors that can arise from the long-term operation of the inertial sensors. Extensive experiments have been conducted to demonstrate that the efficiency of it is superior to the state-of-the-art methods: With the accuracy rate remains the same level, the speed of feature matching is improved by 41.8%. Additionally, when it is applied to simultaneous localization and mapping systems, its localization performances are better than that of the VINS-mono method by 8.1%. • A vision-based multi-layer system-level calibration strategy for IMU is developed. • To determine the predicted position of the feature points, the calibration findings are merged with the feature prediction algorithm based on inertial data. • An error correction approach is provided called "Trust zone" to correct the errors in the location of the expected to feature points. • The zero bias of IMU affects measurement accuracy in the actual workplace has been correct. • A vision-aided online calibration approach is added into the back-end optimization. [ABSTRACT FROM AUTHOR]

• A novel method for designing the micro-thrust measurement system is proposed. • The relationships between design variables and initial conditions and design objectives are established. • Each system parameter is determined using the design criteria of maximizing the system natural frequency. • A sub-micronewton torsional thrust stand with load capacity up to several kilograms is developed. A novel method is developed to determine the key parameters of a micro-thrust measurement system. Firstly, the measurement range, resolution and error of the system to be designed are regarded as the design objectives. Then, the performance parameters of the displacement sensor and the basic properties of the oscillating arm are defined as the initial design conditions. Further, according to the principle of the micro-thrust measurement, the relationships between the main design variables and the initial conditions and the design objectives are established. A criterion of maximizing the system frequency is proposed based on the invariance of generalized stiffness coefficient, and then each design variable is determined based on the above criterion Finally, a sub-micronewton thrust stand is developed using the proposed method, whose system parameters are obtained by the calibration method. The results show that the system parameters meet the design requirements, and the thrust noises corresponding to the underdamped and overdamped conditions are better than 1 μ N / Hz in 0.35 mHz ∼ 1 Hz band and 0.1 μ N / Hz in 9 mHz ∼ 1 Hz band, respectively. [ABSTRACT FROM AUTHOR]

• An error calibration method based on a line-structured light vision sensor is discussed, and the robot's hand-eye and kinematic parameters are calibrated simultaneously by this method. • Based on the principle of differential kinematics, the simultaneous calibration error model is derived, and the robot position error is converted into distance error for the solution. • The LS and LM algorithms are used to identify error parameters, and the error is compensated by an iterative compensation method. • The experimental results show that the proposed method can effectively calibrate the robot's hand-eye and kinematic parameters. For visually guided industrial robots, it is necessary to calibrate the robot's hand-eye relationship to accurately guide the robot's operations with the measurement data of the visual coordinate system. In most cases, the calibration process of hand-eye error does not consider the impact of kinematic errors, which accumulates the error in the calibration process and reduces the calibration accuracy. To enhance the calibration accuracy of industrial robots, a simultaneous calibration method of robot hand-eye relationship and kinematics using a line-structured light sensor is proposed. A simultaneous calibration model is established by using the differential kinematics principle. Afterward, the line-structured light sensor and two standard balls with known center distances are used in the calibration and accuracy verification experiments. After calibration and compensation with the proposed method, the average distance error of the robot declined from 3.967 mm to 1.001 mm. The proposed simultaneous calibration method for hand-eye relationship and kinematics dramatically improves the robot's positioning accuracy. [ABSTRACT FROM AUTHOR]

• The analog-to-digital conversion for the signals of the laser interferometer. • The quadruplicated frequency for the digital signals and the identification for the motion direction. • The count for the digital signals. • The real-time demodulation for the displacement values. • The synchronization between the laser signals and the sensor signals. A high accuracy and real-time amplitude-phase demodulation method based on the pulse counting of optical fringes is proposed for a laser interferometer to realize amplitude and phase measurement of the vibration in primary vibration calibration. The two orthogonally analog signals with high frequency are converted into two digital signals through the comparison module instead of a high-speed data acquisition device. Then one displacement increment during a quarter period of the digital signal can be obtained by the high-frequency clock through comparing the four states of two orthogonally digital signals. The actual output rate of the demodulation data will be decreased by subsample with the vibration frequency. The results of experiment illustrated the deviations were within the limits and the displacement waves were well reconstructed, not only for homodyne interferometer but also for heterodyne interferometer. The proposed method involves less complicated hardware equipment and algorithm, so it is sufficient for real-time and high-precision demodulation of the laser interference signals to realize vibration measurements in primary vibration calibration. [ABSTRACT FROM AUTHOR]

• Analysis of the flow through a calibrated leak; • Knudsen modification of Darcy law; • Accurate modelisation of the relationship between pressure and flow; • Experimental validation of the method. Flow leaks are small devices generating a well-determined flow when subject to a pressure differential (feed pressure). Though, they need to be calibrated against a reference flow based on the feed pressure and fluid density through a complex relation derived from the modified Darcy law, therefore results of a calibration performed in a given condition are not necessarily valid when the leak is used in different conditions. In this paper we will describe a correct renormalization of the calibration results allowing to compute precisely the actual flow rate generated by the leak. A mathematical description of the renormalization will be presented and a method for the experimental determination of the permeability will be discussed. It will be shown that the calibration uncertainty can be reduced by applying the correct normalization, and that the in-use uncertainty can be brought to be of the same order of magnitude as the calibration uncertainty. [ABSTRACT FROM AUTHOR]

• The principle of the absolute hydrostatic leveling system as a means to establish online height datum is proposed. • A non-contact absolute hydrostatic level is designed. • Based on precise measurement of liquid depth, an absolute calibration of the level with an accuracy of 0.031 mm can be achieved. • The validation scheme of AHLS and absolute height accuracy is designed and 2-point AHLS can achieve absolute height with an accuracy of no less than 0.05 mm within a 10 m range. The fourth generation light source HEPS under construction in China demands higher alignment accuracy. However, it is difficult to improve height accuracy based on the overlap method of geometric and tracker leveling. Based on the study of hydrostatic leveling systems for ground settlement monitoring, this paper proposes a new method, Absolute Hydrostatic Leveling System (AHLS), for establishing height datum. The principle of establishing height datum for AHLS is described in detail, and it is emphasized that absolute calibration of the level is crucial for implementing this plan. A set of absolute calibration methods for non-contact absolute hydrostatic level is proposed, including measuring key dimensions of the level and precise measurement of liquid depth. The absolute calibration accuracy reaches 0.031 mm. The height accuracy of validating an AHLS between two points within 10 m using a laser tracker is more than 0.05 mm. The results demonstrate the feasibility of using AHLS to establish absolute height datum with high precision. With this method, the absolute height of each point can be obtained independently without any accumulated errors, allowing the establishment of height datum with high precision on a large scale. This approach can be used in the next generation of accelerator devices and also represents a novel method for achieving high-precision vertical monitoring. [ABSTRACT FROM AUTHOR]

• Created plane-wave measurement model to obtain intensity with associated uncertainty. • Detailed experimental and analytical evaluation of component uncertainties. • Revealed contribution of each component uncertainty to combined uncertainty. • Provided a guide to evaluate the uncertainty in sound intensity measurements. • Improved quality of intensity measurements in multi-input measurement models. Currently, sound intensity instrument calibrations consist of a paired microphone phase and pressure calibrations, and the general uncertainty analysis focuses on how to calculate and express the uncertainty in the pressure lever and phase difference. However, no guidance for intensity level uncertainty is available. A significant barrier is the requirement to develop a measurement model that constitutes a relationship between the output quantities and input quantities, known to be the paired microphone pressure levels and phase difference. The Beijing Aerospace Institute of Metrology and Measurement Technology (AIM) is addressing this issue using a double-coupler calibration system, which is the incentive for the systematic evaluation of the associated measurement uncertainty in this study. A set of methodologies based on the plane-wave model is developed for estimating intensity and particle velocity uncertainty for sound intensity instruments. [ABSTRACT FROM AUTHOR]

To calibrate the test system of fifth-generation (5G) massive multiple-input multiple-output (MIMO) base station (BS), this paper proposes a promising single-port measurement scheme, which is more cost-effective and convenient than conventional scheme. The conventional scheme first requires the disconnection of the measurement equipment from the BS test system, and then uses a costly vector network analyzer (VNA) for the system calibration measurement, which is cumbersome, slow, and inconvenient. Instead, the proposed scheme can conduct the system calibration with low cost directly based on the existing measurement equipment in the original test system, i.e. no need for the extra expensive VNA. The accuracy performance of the proposed scheme is evaluated by the frequency response error measured between the proposed and the conventional schemes, e.g. with an amplitude error range of [ − 0. 45 , 0.14] dB and a phase error range of [ − 0. 2 ∘ , 2. 5 ∘ ]. Therefore, the superiority is that the proposed single-port scheme in this paper accomplished the equivalent measurement as the conventional scheme, and further reduced the cost and inconvenience for the test industry. Finally, the reduced cost and complexity by the proposed measurement scheme is beneficial to both the industry and academic scientific world in terms of faster and more efficient testing as well as increased reproducibility of research findings. • Single-port scheme accomplishes the equivalent measurement as the reference scheme. • Calibration process is done with on need for the extra expensive network analyzer. • Comb generator units boost cost-effective and convenient calibration of test system. [ABSTRACT FROM AUTHOR]

• Actual ratio error of phase B CVT is lower than phase A and phase C. • Only the actual phase error of phase B CVT stay the same as calibration results. • The secondary load plays a decisive role to the error characteristics of CVTs. • The actual secondary load in substations should be applied to any kind of calibration of CVTs. The capacitor voltage transformer (CVT) is one of the most important measurement equipment in the power system, and its measurement accuracy is a key factor to ensure the safety of the power system and the fairness of electricity trade. To ensure the steady-state measurement accuracy, the conventional calibration is carried out to CVTs before operating in substations, and the operating CVTs must be calibrated periodically. However, excessive measurement error often occurs to CVTs which have passed the calibrations. In this paper, the reasons for the inconsistency between calibration results and actual measurement errors are proposed. The calibration in the laboratory, on-site calibration and three-phase operating CVTs are simulated according to actual operating conditions. Both the theoretical analysis and simulation results demonstrate that significant differences exist between the actual measurement errors and the calibration results of CVTs. Some experiments corresponding to the simulations verify the conclusions above. Finally, some suggestions to improve the reliability of calibration results are given. [ABSTRACT FROM AUTHOR]

• Introducing a fitting equation for the calibration results. • Improve the classification and uncertainty of uniaxial testing machines. • Provide an improvement to the international calibration standards/procedures. This paper is devoted to develop calibration and verification procedures for uniaxial material testing machines, by fitting a polynomial equation to the calibration results. The proposed polynomial equation facilitates predicting the behavior of the testing machines at the intermediate forces. Twenty testing machines were calibrated according to ISO 7500-1:2018. For each machine, the indicated forces were correlated to the reference one using polynomial equation and a new source of uncertainty is introduced to contribute in the expanded relative uncertainty as a result of implementing the polynomial equation to interpolate results. The proposed improvement will allows classifying the continuous testing machines which are not classified due to the relative indication error. Two unclassified testing machines were used as a case study to test the efficacy of this proposal. [ABSTRACT FROM AUTHOR]

• An on-site WFT calibration is proposed by using an embedded tri-accelerometer. • The new error model is built for the on-site calibration. • A simple calibration protocol is conducted. • The calibration procedure is fast (less than 10 min) and accurate. • Dynamical tests on soft terrain demonstrates the practicability. Precise online calibration of Wheel force transducer/sensor (WFT) is difficult due to the safety risk of large-scale (kN and kN.m) mass attached on a rolling wheel, the impossibility of applying many loads at precise orientations of the transducer, and the difficulty to avoid the interference under the wheel rotation conditions. To tackle these problems, this paper presents an effective yet fast on-site WFT calibration by using an embedded triaxial accelerometer under the vehicle's gravitational loading conditions. A basic linear model of least-square calibration for the transducer is introduced, followed by the proposed new error model of online calibration. Experiments are performed by the gravitational load of vehicle itself, and compared with the wagon balance to verify the calibration protocol. The tested results demonstrate that the proposed technique provides an accurate, practical, and effective technique for on-line calibrating the WFTs. [ABSTRACT FROM AUTHOR]

• A structural model of direct measurement is introduced with a bottom-up presentation. • The model highlights the role of measuring instruments in measurement. • The model justifies that measurement has both empirical and informational components. • The model explains the role of scales and calibration in measurement. In the last few decades foundations of measurement have developed so as to account for both the role of modeling in measurement, in particular relating to the presence and the effects of measurement uncertainty, and the fact that any measurement is performed by using instruments that work on the basis of transduction effects and provide justified results only in so far as they are properly calibrated. This has triggered a new interest about the role of instruments in the models of measurement. The structure of the process has been variously studied in reference to the connection between measured properties and indications provided by instruments, and to the way in which intersubjective information on the measurand is acquired through instrument calibration. From such a background this paper proposes a comprehensive structural model of direct measurement, whose functional elements, empirical and informational, are presented with a bottom-up strategy as a set of interrelated modules. The result, shown to be a generalization of some of the models currently available in the literature of measurement science, highlights the key role of scales for measurement, clarifies the conceptual and operative relations between direct measurement and calibration, and identifies the principal sources of measurement uncertainty in the structural context of the process. This model is intended to interpret both physical and non-physical measurements, and as such it is a component of a "measurement across the sciences" research programme. [ABSTRACT FROM AUTHOR]

• Low cost rotating arm apparatus is used for low speed calibration. • Hot wire probe is calibrated for very low velocities range from 0 to 0.6 m/s. • Rotating arm method provides simple and in situ calibration. • The proposed method is superior to other techniques for water-based applications. An instrument for calibration of hot-wire probes at very low velocities in water applications is introduced. The technique is based on moving a hot-wire probe by means of a rotating-arm device in still water. This simple in situ calibration method is principally beneficial for the investigations of three-dimensional boundary layers which are encountered for instance over rotating disks. In addition to this proposed technique, an existing alternative method in which the calibration is performed against a known reference velocity over a flat surface of a rotating disk is conducted. The comparison of both methods show that the rotating-arm technique is superior to that existing alternative flat-surface calibration method. [ABSTRACT FROM AUTHOR]

• A novel calibration system for HFM is experimentally and numerically investigated. • An experimental campaign is carried out considering low and moderate heat fluxes. • The absolute method presents a combined standard uncertainty lower than the relative method. • Results of a validated numerical tool show a high heat flux uniformity of the calibration system. • The parametric analysis allows to find the optimal configuration of the calibration system. The estimation and the reduction of thermal transmittance of building envelope components is crucial. Heat Flux Meters (HFMs), instruments devoted to this aim, unfortunately not always are provided with metrological traceability due to the lack of suitable reference standards, especially at critical conditions, such as in the low heat flux regime and low conductivity values. In this paper, the authors propose a novel calibration standard for heat flux meters and discuss the metrological performance of this apparatus operating at critical conditions. Besides experiments, a detailed numerical analysis has been conducted, validating obtained results against measurements. A validated numerical model has then been employed to design, improve and analyze the calibration system in different operating conditions, also through a parametric analysis. Numerical results enabled us to improve and define the required heat flux uniformity in a specific sub-region of the measuring section. [ABSTRACT FROM AUTHOR]

• The significant parameters affecting the accumulation of wet bulk coal material are proposed. • The discrete element parameters of wet bulk coal materials are obtained. • The accuracy of calibration parameters is verified by the funnel test and the slide plate test. To simulate the interactions between the coal mining machinery and bulk coal accurately, the parameters of wet bulk coal were calibrated using the discrete element method (DEM). The influence of discrete element parameters on particle stacking angle was obtained by Plackett-Burman (PB) test. The calibration and verification of these parameters were carried out based on JKR (Johnson-Kendall-Roberts) model. During the calibration, a series of experiment were carried out; the repose angle obtained by the actual test was taken as the response value. The Box-Behnken design (BBD) based on the principle of response surface method (RSM) was applied in calibration. The numerical difference between those repose angles of actual tests and simulation was less than 4.70%, which improved the reliability of the simulation results. The optimal parameter combination could provide a reference for the reasonable selection of simulation parameters of the wet bulk coal using the EDEM software. [ABSTRACT FROM AUTHOR]

• Calibrate whole body segments with only three predefined postures using orientation measurements. • Segmentation procedure segments calibration postures automatically. • Intrinsic average algorithm significantly reduce effect of body shaking. • Iterative hand-eye calibration algorithm directly determine the transformation matrix. This study aims to propose a novel sensor to segment calibration method for magnetic and inertial measurement unit (M-IMU) based human motion capture systems. The calibration procedure is designed to be easily performed by the subject, which can calibrate the whole body segments with only three predefined postures. Firstly, the orientation measurements for each body segment are collected during calibration process. Secondly, a segmentation procedure based on a moving average window algorithm and double-threshold technique is introduced to recognize and segment the calibration postures automatically. To suppress the shaking during the calibration process, an intrinsic average algorithm is presented to smooth the orientation measurements. Finally, an iteration hand-eye calibration approach is utilized to retrieve the sensor to segment calibration matrices. The error due to the ungraded calibration postures can be reduced observably, and we also define an indicator to evaluate the quality of the performed calibration postures. The calibration procedure has been validated on several subjects using a wearable M-IMU based motion capture system. Experiment results show that the proposed calibration method can suppress the shaking disturbances effectively, and has good repeatability. [ABSTRACT FROM AUTHOR]