Repeatability Error Research Articles

A rapid resistance measurement system for quartz pendulums

A quartz pendulum, gold plated on both sides, is the core component of a quartz accelerometer. Currently, a two-wire manual measurement method is employed to measure the resistance at 24 key positions on the gold plating to evaluate manufacturing quality. This method is time-consuming and has poor repeatability. In this paper, an automatic measurement system is proposed to measure these 24 resistances. The proposed system consists primarily of a lab-designed holder that clamps the sample, a machine vision unit to measure the sample position, RXY-stages for precise positioning, two lab-designed probes with 48 needles to sense the electrical signals, a multichannel self-switching module to sample the electrical signals from the probe needles, and a 7½-digital multimeter to measure the resistances. In addition, a simple, precise pre-measurement positioning method is introduced here. Experimental results show that the quartz-pendulum resistances can be measured quickly and precisely using the proposed system. The measurement rate of 1 pendulum/min is a factor of 10 faster than the current manual method, the measurement stability error is only 0.9 mΩ (a relative error of 0.13%), and the measurement repeatability error is 1.2 mΩ (a relative error of 0.20%).

Characterization of a Newly Designed Vacuum Valve Having a Variable Conductance Function

A valve has a function of controlling the flow of a fluid by opening or closing a passage. A valve can thus be used to create different pressures for the two areas on either side of the valve. However, the conventional vacuum valve has a problem that the flow rate of the gas cannot be controlled. In this light, it is necessary to develop a vacuum valve that is capable of precisely controlling the flow rate of the gas without leakage of the gas. Recently, we developed a variable conductance vacuum valve to control the inlet pressure for the vacuum chamber. The variable conductance valve developed in this study uses a similar iris structure to that of conventional control valves employed in normal water and sewage pipes, but the valve has no outer mounting hole or fastening holes for coupling the driving parts because the iris structure is changed in a non-contact manner by a magnetic field. Therefore, the valve in this study has the advantage that the fluid leakage of the valve can be completely blocked without a separate device such as packing or sealing components or an O-ring, and therefore, the internal vacuum state can be maintained. The fabricated valve showed a relative repeatability error within 0.5% and a relative reproducibility error within 5%. These results demonstrate that the conductance variable valve developed in this study is suitable for easily changing the pressure inside a vacuum chamber by adjusting the conductance.

Fourier interferometry of multi-layer sample using wavelength tuning and partially negative window

When measuring the thickness of a transparent plate using wavelength tuning-based phase modulation fringe analysis, the nonlinearity of the phase modulation can cause both a nonuniform phase error and a bias phase error. In this study, a method of eliminating the bias phase error using the characteristic polynomial theory was developed and a flexible 4 N − 1 algorithm, consisting of a partially negative window and a discrete Fourier transform term, was constructed. The behaviors of the 4 N − 1 algorithm were visualized in the frequency domain. The error compensation ability was estimated by comparing it to conventional algorithms. The thickness and surface profile of a lithium niobate wafer were simultaneously measured using a Fizeau interferometer and the proposed 4 N − 1 algorithm. The experimental results showed that the 4 N − 1 algorithm performs better than other algorithms in terms of the repeatability error and suppression of the bias phase error.

In vivo repeatability of homogenized finite element analysis based on multiple HR-pQCT sections for assessment of distal radius and tibia strength.

Micro finite element analysis (μFE) is a widely applied tool in biomedical research for assessing in vivo mechanical properties of bone at measurement sites, including the ultra-distal radius and tibia. A finite element approach (hFE) based on homogenized constitutive models for trabecular bone offers an attractive alternative for clinical use, as it is computationally less expensive than traditional μFE. The respective patient-specific models for in vivo bone strength estimation are usually based on standard clinical high-resolution peripheral quantitative CT (HR-pQCT) measurements. They include a scan region of roughly 10mm in height and are referred to as single-sections. It has been shown, that these small peripheral bone sections don't reliably cover the fracture line in Colles' fractures and therefore the weakest region at the radius. Recently introduced multiple section (multiple adjacent single-sections) measurements might improve the evaluation of bone strength, but little is known about the repeatability of hFE estimations in general, and especially for multiple section measurement protocols. Accordingly, the aim of the present work is to quantify repeatability of clinical in vivo bone strength measurement by hFE on multiple section HR-pQCT reconstructions at the distal radius and tibia. Nineteen healthy Swiss women (43.6y±17.8y) and twenty men (48.2y±19.4y) were examined with HR-pQCT at 61μm isotropic voxel resolution. Each subject was first scanned three times using a double-section (336 slices) at the distal radius and then three times using a triple-section (504 slices) at the distal tibia. The multiple section HR-pQCT reconstructions were graded for motion artefacts and non-linear hFE models (radius and tibia) and linear μFE models (only radius) were generated for estimation of stiffness and ultimate load. Then in vivo repeatability errors were computed in terms of root mean square coefficients of variation (CV). In vivo repeatability errors of non-linear hFE stiffness (S) and ultimate load (F) were significantly higher at the radius (S: 2.71% and F: 2.97%) compared to the tibia (S: 1.21%, F: 1.45%). Multiple section linear μFE at the radius resulted in substantially higher repeatability errors (S: 5.38% and F: 10.80%) compared to hFE. Repeatability errors of hFE outcomes based on multiple section measurements at the distal radius and tibia were generally lower compared to respective reported single-section μFE repeatability errors. Therefore, hFE is an attractive alternative to today's gold standard of μFE models and should especially be encouraged when analyzing multiple section measurements.

Multiblock Analysis Applied to TD-NMR of Butters and Related Products

This work presents a novel and rapid approach to predict fat content in butter products based on nuclear magnetic resonance longitudinal (T1) relaxation measurements and multi-block chemometric methods. The potential of using simultaneously liquid (T1L) and solid phase (T1S) signals of fifty samples of margarine, butter and concentrated fat by Sequential and Orthogonalized Partial Least Squares (SO-PLS) and Sequential and Orthogonalized Selective Covariance Selection (SO-CovSel) methods was investigated. The two signals (T1L and T1S) were also used separately with PLS and CovSel regressions. The models were compared in term of prediction errors (RMSEP) and repeatability error (σrep). The results obtained from liquid phase (RMSEP ≈ 1.33% and σrep≈ 0.73%) are better than those obtained with solid phase (RMSEP ≈ 5.27% and σrep≈ 0.69%). Multiblock methodologies present better performance (RMSEP ≈ 1.00% and σrep≈ 0.47%) and illustrate their power in the quantitative analysis of butter products. Moreover, SO-Covsel results allow for proposing a measurement protocol based on a limited number of NMR acquisitions, which opens a new way to quantify fat content in butter products with reduced analysis times.

Measurement of Multi-Component Hydraulic Loads With Compensation of Dynamic Load

Due to rotational inertia, it is difficult to obtain accurate results of high-precision dynamic multi-component force or loads using traditional approaches including the theoretical calculations, simulations, and measurement. To minimize the impact of moment of inertia on dynamic measurement results, a two-stage measurement approach is proposed and tested in this paper. The proposed measurement approach based on synchronizing the measuring device with the shaft rotation. Piezoelectric sensors with wide frequency broadband ranges and high stiffness in contrast to strain gauges are adopted to measure the multi-component force based on the biaxial load cells. Static calibration of the measuring device has been studied to decouple the multi-component force. The corresponding maximum linearity, repeatability and interference error is 0.91 %, 1.82 %, and 1.38 % respectively. The interference error has been improved largely from 15.81 % before the adoption of static calibration. Another noticeable advantage from the proposed approach illustrates that the actual radial force is 26.97 %, which is a significant correction of the measurement results without compensation. The experimental results show that the proposed dynamic compensation method can effectively address the existing moment of inertia problem which could benefit the measurements of high-speed rotating machinery.

Study on Micro Force Sensor and its Signal Acquisition System Based on Android and Arduino

Force sensor becomes more and more miniature in order to achieve precise measurement in small place. A magnetostrictive micro sensor was proposed in the paper; meanwhile, the signal acquisition system was designed by Android platform and Arduino MCU to meet the popular mobile terminal. The structure of sensor and the hardware and software of system were designed to realize the functions of force signal acquisition, processing and analysis, and upload the data to mobile terminal in real time. It can be seen from the experimental tests: Firstly, the volume of sensor was less than 2 cm3 and had good linearity, while the sensitivity was 0.1537 mV/N and the repeatability error was 1.07%. Secondly, the system could effectively enlarge the output value of sensor more than 100 times and the nonlinear error was less than 1.5%, while the linearity and sensitivity can be kept well. This sensor with acquisition system had the advantages of easy realization, low cost, strong expansibility and simple operation, and it can be widely used in industrial control, mechanical automation, intelligent robot, and so on. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Optimization of design and measurement principle of six-components force/thrust measurement stand

Purpose The purpose of this study is to present the optimization of the design and measurement principle of a six-component force/thrust measurement stand. This study highlights some key problems found in previous studies and proposes improvements in design and measurement principles. Design/methodology/approach The numerical simulation approach is used to verify the proposed improvements. An improved design and measurement principle are proposed and to verify the proposed improvements, simulation experiments are conducted. The data obtained from simulations are analyzed through the proposed improved measurement principle. The proposed stand is capable of measuring the main thrust and other components as pitch, yaw and roll. The stand is capable of measuring the main thrust more than 50,000 N and orthogonal thrust components more than 1,000 N. Improved design of measurement stand is also capable of measuring moments in three-axis more than 150 Nm. Thrust stand consists of two main sections: front and rare. Stand consists of seven piezoelectric force sensors to measure all components of force. Findings The simulations experiments and basic theoretical laws of kinematics prove that the proposed design indeed improves the precision of measurement and also enhance the efficiency of design. Evaluation results show that the measurement stand designed is highly functional. Non-linearity, coupling and repeatability errors are found to be within acceptable range during numerical simulations. Originality/value This study is unique in this kind. This study identifies the key problems found in previous studies and proposes an improved design and measurement principle. This study provides evidence for the improvements to be really functional and necessary.

A high-precision laser method for directly and quickly measuring 21 geometric motion errors of three linear axes of computer numerical control machine tools

Error compensation has become an important means of improving the manufacturing and processing accuracy of computer numerical control (CNC) machine tools. Quick and precise measurement of the various geometric motion errors (GMEs) of CNC machine tools is crucial. We propose a novel laser method for the efficient and direct high-precision measurement of the 21 GMEs of a three-axis CNC machine tool, or three linear axes of a five-axis tool. A corresponding system was developed, comprising a fiber-coupled laser unit, sensor head, target unit, and beam-steering unit. The beam-steering unit was designed to perform high-accuracy 90° rotation of the measuring beam, and the target unit was designed to be sensitive to 18 GMEs of the three linear axes. Stability, repeatability, and comparison experiments were conducted to verify the performance of the proposed system. The results showed that the stability of the position error measurement is ± 6.3 nm. For straightness error measurement, the stability, repeatability error, and residual are within ± 60.3 nm, ± 0.5 μm, and ± 0.7 μm, respectively. These are within ± 0.12 arcsec, ± 0.5 arcsec, and ± 0.5 arcsec for the pitch and yaw measurements, and within ± 0.37 arcsec, ± 1.5 arcsec, and ± 1.0 arcsec for the roll measurements, respectively. For squareness error measurement, the repeatability error and residual are within ± 0.6 arcsec and ± 1.6 arcsec, respectively. Compared with a laser interferometer, the proposed system can measure the 21 GMEs of a three-axis machine tool with one-step installation. Without accuracy loss, the measurement efficiency is approximately 45 times higher than that of a laser interferometer, thus providing a new quick and accurate measurement method of GMEs and error compensation of CNC machine tools.

Study of using cutting chip color to the tool wear prediction

In this study, the correlation between chip surface chromaticity and wear of cutting tools is established through experiments, and a system for judging and predicting tool wear by observing chip color is proposed. At present, the life prediction of cutting tools is indirectly measured and predicted by using vibration and current. In this study, chip color change is used to predict tool wear, and back-propagation Artificial Neural Networks (ANN) is used to predict and verify. The average error percentage between the predicted value and the actual value of tool wear is only 1.73% and 1.66%, respectively, which was confirmed by cutting test and verification experiments. This study uses Taylor’s tool life model and chip color to analyze, and after repeated tests and experimental analysis, the average error of repeatability is 4.5%. In the verification of stainless steel cutting hard-cutting materials, the equipment accuracy is between 0.5 and 3.0 color difference values of grade 2 to 3. Therefore, the measurement and model establishment of the system can accurately and quickly predict tool wear. In prediction experiment and analysis, the back neural network is used for test, the maximum error ranges are 0.0012 mm and 0.0097 mm, the mean error percentages are only 1.73% and 1.66%.

Optical fiber dosimeter for real-time in-vivo dose monitoring during LDR brachytherapy.

An optical fiber sensor for monitoring low dose radiation is presented. The sensor, based on radiation sensitive scintillation material, terbium doped gadolinium oxysulphide (Gd2O2S:Tb), is embedded in a cavity of 700µm diameter within a 1mm plastic optical fiber. The sensor is compared with the treatment planning system for repeatability, angular dependency, distance and accumulated radiation activity. The sensor demonstrates a high sensitivity of 152 photon counts/Gy with a temporal resolution of 0.1 seconds, with the largest repeatability error of 4.1%, to 0.361mCi of Iodine-125 the radioactive source most commonly used in LDR brachytherapy for treating prostate cancer.

A novel apparatus to measure the biomechanical properties of blood vessels

PurposeThe study of vascular mechanics is important. The purpose of this paper is to present an apparatus to measure the biomechanical properties of blood vessels, which can be used for tensile test and fatigue test.Design/methodology/approachThis equipment consists of a mechanical test platform, a hardware circuit based on FPGA and control software. The torque generated by stepper motor is converted to axial force by ball screw, and the vascular specimen is stretched axially. The tension is measured by a load cell, and the displacement is recorded by a grating displacement sensor.FindingsAccording to the results of calibration experiment and stability experiment, the linearity error of the system is 0.251, the hysteresis error is 0.047, the repeatability error is 0.185, the comprehensive error is 0.315 and the standard deviation of the output is less than 0.01 N. A test of animal vascular mechanical properties was carried out, and the results are consistent with the theory.Originality/valueThis apparatus is designed to measure biomechanical properties of blood vessels, and the results of experiments indicate that it is stable and reliable. This work is valuable for studying vascular disease and testing artificial blood vessels.

Do we need the third dimension? Quantifying the effect of the z-axis in 3D geometric morphometrics based on sailfin silversides (Telmatherinidae).

This study investigated the impact of the third dimension in geometric morphometrics (GM) using sailfin silversides (Telmatherinidae) from the Malili Lakes of Sulawesi (Indonesia). The three morphospecies of the monophyletic "roundfin" radiation are laterally compressed and vary in shape traits. The results of 2D and 3D GM were compared and quantified to discuss the advantages and disadvantages of both methods for closely related species and their sexes. This approach focused on the head because it is far more complex and three-dimensionally structured than the trunk or the caudal region. The results revealed no significant benefit concerning repeatability and measurement error in 3D GM compared to 2D GM. The z-axis contributed substantially to the variance of the 3D data set but was irrelevant for discrimination of species and sexes in the approach. Limited gain in information was contrasted by substantially higher effort for 3D compared to the 2D analyses. The study concluded that 2D GM is the more efficient shape analysis approach for discriminating roundfins. Broader studies are needed to test which of the two methods is more efficient in distinguishing laterally compressed fishes in general. For future studies, due to the high investment required, this study recommends carefully evaluating the necessity of 3D GM. If in doubt, this study suggests testing for congruence between 2D and 3D GM with a subsample and consequently applying 2D GM in the case of high congruence.

Diaphragm-Micro-Stylus-Based Fiber Bragg Grating Tactile Sensor

We propose a simple and novel circular diaphragm-micro-stylus based single fiber Bragg grating (FBG) tactile sensor for reading Standard English Grade-1 Braille cells. The surface protrusions on the cells are transduced into strain variations on the FBG sensor, bonded along the line of symmetry of the diaphragm, by a free, vertically moving Micro-Stylus (MS). The tension mode of the diaphragm and the mass of the micro-styli are varied to optimize the sensing properties of the system. The maximum sensitivity of 1.786nm/mm is exhibited by the sensor system with the highest mass of the MS (MS-1; 167mg) in the highest tension mode (770μe). The repeatability error and resolution of the sensor in the aforementioned configurations are found to be 0.028nm and 559nm respectively. The proposed sensor system displayed good linearity, repeatability, high resolution, and easily adjustable sensitivity in the present scenario.

Influences of annealing temperature on the thermoelectric properties of thin film thermocouples based on a flexible substrate by RF magnetron sputtering

Thin film thermocouples (TFTCs) made up of indium tin oxide (ITO) and indium oxide (In2O3) are designed and fabricated on a flexible substrate (polyimide) by radio frequency magnetron sputtering to satisfy the application needs of real-time monitoring of the surface temperature of non-planar objects. The microstructure and thermoelectric property of TFTCs are investigated under different annealing temperatures and the results show that the best annealing treatment result is achieved at 200 °C for 1 h. After the annealing treatment, the temperature resolution of the flexible TFTCs can reach 0.1 °C, and the hysteresis error and repeatability error can reach 2.06% and ±1.287%, respectively. An electromotive force (EMF) experiment shows that the average Seebeck coefficient of flexible TFTCs annealed at 300 °C can reach 56.90 µV °C−1 which is more than 8.5 times higher than the unannealed ones when the temperature difference is 200 °C. In addition, different output characteristics are obtained when TFTCs are placed on the inner and outer surfaces with different curvatures. Keeping the temperature difference between the hot and cold ends of the TFTCs constant, the flexible TFTCs also have the ability to measure the angle by measuring the EMF. The sensors show good application potential in temperature measurement in a curved plane and the measurement of the curvature of a curved surface.

RT-qPCR for the diagnosis of the vesiculovirus Cocal virus.

Cocal virus (COCV) is one of the causative agents of vesicular stomatitis, presenting clinical signs indistinguishable from those caused by foot-and-mouth disease virus (FMDV). Therefore, the differentiation of these two viruses via laboratory diagnosis is essential. The objective of this study was to develop and validate a real-time quantitative PCR (RT-qPCR) protocol for the diagnosis of COCV directly from epithelial samples. The method developed had 97% accuracy at 3950 pfu and a repeatability error of 1.29%. RT-qPCR was able to distinguish COCV from other viruses that cause vesicular diseases, an important factor because seroneutralization may produce cross-reactivity between COCV and vesicular stomatitis Alagoas virus (VSAV). No epithelial sample originating from vesicular disease outbreaks between 2014 and 2018 in Brazil was positive for COCV.

The coupling of scattered-bend loss in POF based the displacement measurement sensor

In this paper, a displacement sensor is proposed based on the coupling of scattering loss during the bending of fiber. We adopted a twisted structure of two fiber to couple the scattered loss which caused by bending. Two polymer optical fiber were used in the experiment and the fibers were twisted and bent. When the fiber draft then the bent radius becomes shorter. The scattered-bend loss was arisen from illuminating fiber and being coupled in receiving fiber. The proposed sensor has range about 150 mm and the sensor used for static, dynamic and plane-in-out measurement. The sensor has good linearity between 0 mm to 80 mm, having the sensitivity of 1.26 nW\\mm, resolution of 0.79 mm, and repeatability error of 1.26%. The design structure of the sensor is simple, holistic and cost-effective and has potential advantages on industrial application.

Ultra-small pressure sensors fabricated using a scar-free microhole inter-etch and sealing (MIS) process

This paper presents a tiny 0.4 mm × 0.4 mm piezoresistive absolute pressure sensor chip with a fabrication cost as low as 0.01 US$/die. With the thin-film under bulk-silicon technique, a very thin but uniform poly-silicon pressure-sensing diaphragm is formed beneath a bulk-silicon beam-island structure to accommodate piezoresistors. The thin diaphragm exhibits a high sensitivity, and the beam-island-reinforced structure helps reduce deflection and improve linearity. The sensor is fabricated using a novel scar-free micro-hole inter-etch and sealing (MIS) process. In this newly developed process, seals are removed from the diaphragm area and placed on both the single-crystalline silicon island and single-crystalline silicon frame surrounding the poly-silicon diaphragm. Thus, the thin diaphragm is kept flat and smooth, thereby enhancing the sensing performance and fabrication yield. More importantly, the diaphragm-beam-island structure is small enough to fabricate sensor chips as small as 0.4 mm × 0.4 mm. With the high-yield process, a very low fabrication cost of 0.01 US$/die is realised owing to a high throughput of 90 000 die per 6 inch wafer. The ultra-small and low-cost pressure sensor exhibits sensitivity of 0.88 mV kPa−1/3.3 V, hysteresis of 0.15% full scale (FS), repeatability error of 0.04% FS, and non-linearity of 0.10% FS. Without any additional thermal compensation method, the sensor exhibits a low temperature coefficient of zero-point offset of −0.064%/°C FS and a temperature coefficient of sensitivity (TCS) of −0.22%/°C within the temperature range from −25 °C to +85 °C, at a full measurement range (i.e. full scale) of 100 kPa. With the new scar-free MIS process, the presented pressure sensor looks promising for smartphones, drones, and other consumer-electronic applications.

Investigation of Different Compression Apparatus Usage Effects in Calibration Process of Strain Cylinders

In this article, in calibration process of strain cylinder, which is performed according to ISO 376 standard, effect of loading apparatus with different dimensions on measurement result has been investigated. In addition, relative repeatability error of calibration on measurement results, temperature fluctuation, accuracy error of measurements, creep error, as well as the stability and metrological characteristics of indicator have been examined. As a result, it has been determined that use of loading pads with different diameters has significantly affected metrological performance of strain cylinder.

Precise Measurement of the Surface Shape of Silicon Wafer by Using a New Phase-Shifting Algorithm and Wavelength-Tuning Interferometer

In wavelength-tuning interferometry, the surface profile of the optical component is a key evaluation index. However, the systematic errors caused by the coupling error between the higher harmonics and phase shift error are considerable. In this research, a new 10N − 9 phase-shifting algorithm comprising a new polynomial window function and a DFT is developed. A new polynomial window function is developed based on characteristic polynomial theory. The characteristic of the new 10N − 9 algorithm is represented in the frequency domain by Fourier description. The phase error of the new algorithm is also discussed and compared with other phase-shifting algorithms. The surface profile of a silicon wafer was measured by using the 10N − 9 algorithm and a wavelength-tuning interferometer. The repeatability measurement error across 20 experiments was 2.045 nm, which indicates that the new 10N − 9 algorithm outperforms the conventional phase-shifting algorithm.