High-accuracy ultrasonic temperature measurement based on MLS-modulated continuous wave

Ultrasonic temperature measurement has the potential to improve measurement accuracy by increasing the length of a received signal due to its excellent performance with noise resistance. However, when the distance between the transmitter and receiver is limited, the received signal can be polluted by strong multiple echoes, which can significantly degrade temperature accuracy. This paper proposes a method for high-resolution ultrasonic temperature measurement. With the use of a maximum length sequence (MLS)-modulated continuous wave, the obstructive effect of echoes is effectively suppressed. A hybrid method is employed for accurate time-of-flight (TOF) estimation by incorporating both cross-correlation and phase shift (PS), which is the basis of highly accurate temperature measurement. The experimental results in distilled water show that the proposed method estimates TOF with a standard deviation of less than 0.3 ns, and temperature errors consistently remain within ±0.04 °C.     

Application of ultrasonic Doppler velocimetry to molten glass by using broadband phase difference method

An ultrasonic velocity profile (UVP) measurement in high temperature molten glass was presented using buffer rod technique. A ceramic buffer rod was used to transmit ultrasound into molten glass. The rod had a taper shape and porous cladding to suppress trailing echo, which is the spurious echo in the buffer rod measurement. The broadband signal processing method was presented to improve noise tolerance in velocity estimation. This method is based on the phase difference method, which is originally proposed as a narrowband method. Measurable distance of the UVP measurement was investigated combining the buffer rod and the broadband signal processing method. Experiment was conducted at the temperature from 1000 °C to 1200 °C. As a preliminary test, motion tracking in molten glass was successfully demonstrated.     

Quasi-constant rotational stiffness characteristic for cross-spring pivots in high precision measurement of unbalance moment

This paper proposes a design method for cross-spring pivots with quasi-constant rotational stiffness in the field of unbalanced moment measurement. To achieve high precision measurement of unbalance moment, the relationship between instrument sensitivity and the rotational stiffness of the cross-spring pivot is revealed. In order to eliminate the impacts of payload changes on instrument sensitivity, the relationship between geometric parameters and the rotational stiffness of the pivot is studied. Further, cross-spring pivots with quasi-constant rotational stiffness are designed as the rotation unit of a static balancing instrument, while the center shift of pivot takes the minimum value. Certain amount of unbalance moments is measured by the instrument. Experimental studies of the instrument show that the maximum measurement errors of unbalance moments 0.162 g mm, 0.319 g mm and 1.300 g mm are 0.068 g mm, 0.086 g mm and 0.053 g mm, respectively, when the payload ranges from 0 g to 7000 g. The instrument can achieve a relatively high precision measurement and the instrument sensitivity is almost not affected by the changes of payloads. The effectiveness of the method and the stiffness property of the pivot are verified by the experiments. So this kind of pivot has good prospects in unbalance moment measurement.     

Wind speed and direction measurement based on arc ultrasonic sensor array signal processing algorithm

This article investigates a kind of method to measure the wind speed and the wind direction, which is based on arc ultrasonic sensor array and combined with array signal processing algorithm. In the proposed method, a new arc ultrasonic array structure is introduced and the array manifold is derived firstly. On this basis, the measurement of the wind speed and the wind direction is analyzed and discussed by means of the basic idea of the classic MUSIC (Multiple Signal Classification) algorithm, which achieves the measurements of the 360° wind direction with resolution of 1° and 0–60 m/s wind speed with resolution of 0.1 m/s. The implementation of the proposed method is elaborated through the theoretical derivation and corresponding discussion. Besides, the simulation experiments are presented to show the feasibility of the proposed method. The theoretical analysis and simulation results indicate that the proposed method has superiority on anti-noise performance and improves the wind measurement accuracy.     

Analysis of tunnel displacement accuracy with total station

The remote distance measurement (RDM) method requires only common total stations and not special post-processing software. Moreover, this method is easy to operate and highly accurate results can be obtained. Therefore, RDM is used in the displacement monitoring of tunnel engineering. This study presents the calculation formulas for the crown settlement and wall convergence of tunnel as measured by RDM with total station. The mean error formulas are derived based on error propagation laws. When tunnel displacements measured by using total station with the m_s not more than 2 mm + 2D ppm (D is the measurement distance) and m_α not more than 1″, the horizontal distance between the rear viewpoint and the monitoring section is in the range of 50–150 m, the horizontal distance between the total station and the monitoring section ranges from 40 m to 60 m, and the total station is near the tunnel centerline, the measurement accuracy can reach 1 mm.     

The fault feature extraction and classification of gear using principal component analysis and kernel principal component analysis based on the wavelet packet transform

The vibration signal of a gear system is selected as the original information of fault diagnosis and the gear system vibration equipment is established. The vibration acceleration signals of the normal gear, gear with tooth root crack fault, gear with pitch crack fault, gear with tooth wear fault and gear with multi-fault (tooth root crack & tooth wear fault) is collected in four kinds of speed conditions such as 300 rpm, 900 rpm, 1200 rpm and 1500 rpm. Using the method of wavelet threshold de-noising to denoise the original signal and decomposing the denoising signal utilizing the wavelet packet transform, then 16 frequency bands of decomposed signal are got. After restructuring the decomposing signal and obtaining the signal energy in each frequency band, the signal energy of the 16 bands is as the shortlisted fault characteristic data. Based on this, using the methods of principal component analysis (short for PCA) and kernel principal component analysis (short for KPCA) to extract the feature from the fault features of shortlisted 16-dimensional data feature, then the effect of reducing dimension analysis are compared. The fault classifications are displayed through the information that got from the first and the second principal component and kernel principal component, and these demonstrate they have a different and good effect of classification. Meanwhile, the article discusses the effect of feature extraction and classification that caused by the kernel function and the different options of its parameters. These provide a new method for a gear system fault feature extraction and classification.     

Accurate ultrasound speed measurement using an MLS-modulated continuous wave

The continuous wave shows greater potential than the pulse signal to achieve high-accuracy ultrasound speed measurement thanks to its stronger noise resistance. However, the accuracy of ultrasound speed measurement would deteriorate if echoes exist in the received continuous wave. This paper presents an applicable method using the maximum length sequence-modulated continuous wave. The present method improves the accuracy of ultrasound speed measurement further by resisting echoes. The time delay between the received signal and the transmitted signal is estimated accurately by combining the cross-correlation, parabolic interpolation and phase shift technique. Moreover, both the inherent delays induced by physical system and the path length of ultrasound are expediently corrected through least square estimation. As a result, accurate time of flight and ultrasound speed measurement are achievable. For example, the standard deviation of ultrasound speed measurement in distilled water is less than 0.003 m/s, and the deviation between the ultrasound speed measurement and the reference is less than 0.04 m/s.     

Measurement and analysis of fluorescent whitening agent content in soybean milk based on image techniques

This paper presents a method for measuring and quantitatively analyzing the fluorescent whitening agent in soybean milk based on image techniques. After collecting the fluorescent images of the soybean milk samples, the top seven wavelet moment invariants are selected according to the sample training and experimental comparison. Then calculate the standard templates of the 49 classes of calibration samples with different fluorescent whitening agent content ranging from 0.02 mg/ml to 0.5 mg/ml. The minimum distance method is carried out to match the testing sample with the calibration template, which realizes the quantitative analysis. To verify the effectiveness of the presented method, the prediction experiment is carried out. Results show that the absolute errors are within 0.005 mg/ml and the relative errors are within 5%, which means this method can measure the fluorescent whitening agent in soybean milk. This research presents a new approach for detecting the illegal fluorescence additive in food production.     

Development of side wall type permanent magnet flowmeter for sodium flow measurement in large pipes of SFRs

Sodium cooled Fast Reactors (SFR) require measurement of liquid sodium flow in its primary and secondary circuits. For the primary system of the pool type concept of SFR design, flowmeters have to be immersed in sodium pool and require flow sensors which can withstand high temperatures up to 550 °C, nuclear radiation and chemically reactive sodium environment. Secondary circuits and safety grade decay heat removal (SGDHR) circuits of SFR need flow measurement in stainless steel (SS) pipes of diameter varying from 15 mm to 800 mm. For small pipes, flowmeters with permanent magnet flowmeter with ALNICO-V magnet assembly is the unanimous choice. Conventional permanent magnet flowmeters (PMFM) for large pipelines become bulky, heavy and have installation problems. For sodium flow measurement in large pipelines a few other alternate methods are considered. In the case of Prototype Fast Breeder Reactor (PFBR), which is at an advanced stage of construction at Kalpakkam, flow in the 800 mm diameter secondary main circuit is measured by means of a bypass flowmeter. Other sensors that could be deployed include eddy current flowmeters (ECFM), which are introduced into the pipe to measure flow velocity in the pipe, ultrasonic flowmeters and permanent magnet based side wall flowmeters. In permanent magnet based side wall flowmeter (SWFM), a permanent magnet block is mounted on one side of the large pipe and the magnetic field produced by the magnet penetrates through the pipe and interacts with the flowing sodium and induces an electro motive force (emf) proportional to the flow. This is a compact, cost effective and fairly accurate method for flow measurement in large pipelines of SFR circuits. SWFM is suitable for pipelines of 100 mm and above. In the present work a side wall flowmeter for 100 mm pipe is designed, manufactured, calibrated and tested in an existing sodium facility. Voltage signal developed in SWFM for different flowrates was simulated with three dimensional Finite Element Model (FEM) and validated with experimental results. Effect of asymmetric magnetic field on flowmeter voltage signal and dependence of flowmeter voltage signal on position of electrodes was also analyzed with model. The feasibility of use of this type of flowmeter for large pipelines of SFRs is demonstrated.     

Development and calibration of an integrated 3D scanning system for high-accuracy large-scale metrology

Quality control in advanced manufacturing requires automated and high-accuracy large-scale 3D measurement. This paper proposes a high-accuracy, low-cost 3D scanning system by integrating industrial robot with precise linear rail and laser sensor. The measuring principle and system construction of the integrated system are introduced in detail. A mathematical model is established for mapping the change of the laser sensor frame while it scans along the linear rail and a sphere-based algorithm for rail orientation calibration is introduced. Subsequently, taking the robot positioning error into consideration, an enhanced hand–eye calibration method is proposed to determine the relationship between robot end-effector and rail scanning frame. Validation experiments were performed, a maximum distance error of 0.071 mm was detected within the rail range and a mean/maximum distance error of 0.309/0.604 mm was detected in the robot volume. A large-scale scanning instance also shows that integrated robotic scanning system features high-efficiency and high-accuracy.     

Drop swarm analysis in dispersions with incident-light and transmitted-light illumination

The new developed Optical Multimode Online Probe (OMOP) can process images from either incident-light illumination (also called epi-illumination) or transmitted-light illumination (also called trans-illumination). The probe has an outer diameter of 38 mm and the illumination is achieved by high performance Light Emitting Diodes (LEDs) with specifications of 1.96 mm² and 493 lm (251.53 lm/mm²) at an angular deviation of 0.37°. A camera probe is used with either an object-space telecentric (telecentricity <0.2°, 2437 mm virtual pupil distance) or entocentric objective (Köhler based illumination, 6238 mm virtual pupil distance). Using the telecentric mode, the particle distance independency is located within 20 mm while the focal depth is approximately 5 mm. The local resolution is between 20 and 30 μm, according to the used optics, with a standard deviation less than 4.5%. Maximum particle diameter is up to 5 mm while particles can reach up to 2 m/s as function of exposure. The basic distance transform approach with watershed segmentation for analysis of transmitted-light images gives deviations less than 5% at high particle densities and less than 2% at low ones. The error of false positives typically is below 5% while the error of wrong radiuses is below 1% for up to 90% of all droplets and below 5% otherwise. Up to five images per core and second (trans-illumination) can be analyzed automatically and online at densities up to 25% (trans-illumination, gap width less than 5 mm) 40% (object side telecentric epi-illumination, single probe) respectively.The advanced pre-segmentation approach based on the Random Forest Classifier (RFC) is used to perform the more complex image analysis with epi-illumination. As long as the quality of pre-segmentation is high enough, the classification results in images, which can be analyzed in the following distance transform approach. This is considerably depending on the quality of training the algorithm and recurring image features. Compared to the distance transform analysis at low densities the deviation increases. The RFC pre-segmented image gives an additional deviation of 1.1% (both in regard to the total amount of evaluated pixels) and a deviation of 12.9% in regard to the mean particle diameter. Below a particle size of 50 pixels the image analysis overestimates the actual number of particles due to the sensitivity of the Euclidian distance approach.     

An experimental method to measure the layer thickness and wave velocity of copper–steel composite board without interface echo

Thickness of each medium layer and velocity of ultrasonic wave propagation in each medium layer of the two-layer composite medium were measured simultaneously based on the method to collect phase information from continuous echo signals on front surface and undersurface. Such measurement was implemented under no interface echo and fixed total thickness of the testpiece. The method can be applied to any two kinds of two-layer composite medium. The paper only used a 35 mm thick copper–steel composite board as an experimental example. Calculated results demonstrated that measuring errors of both thickness and velocity of ultrasonic wave propagation are smaller than 0.2%, indicating the effectiveness of the proposed measurement method.     

Uncertainty analysis for a phase-detector based phase noise measurement system

Phase noise is an important parameter to characterise the frequency stability of oscillators and synthesised signal generators. Accurate measurement of phase noise is required for various applications in radar, communication and navigation systems. A single-channel phase-detector based phase noise measurement system is described. The system’s measurement errors and uncertainties have been analysed in details. The expanded uncertainty is about 2.7 dB for calibrating phase noise of a signal generator at 0.001–1.6 GHz for frequency offsets from 1 Hz to 100 kHz. The uncertainty budget for measuring a signal generator’s phase noise at 640 MHz is also presented.     

Application of Monte Carlo simulation for estimation of uncertainty of four-point roundness measurements of rolls

Large-scale rotors in the paper and steel industry are called rolls. Rolls are reground at regular intervals and roundness measurements are made throughout the machining process. Measurement systems for roundness and diameter variation of large rolls (diameter <2000 mm) are available on the market, and generally use two to four sensors and a roundness measurement algorithm. These methods are intended to separate roundness of the rotor from its movement. The hybrid four-point method has improved accuracy, even for harmonic component amplitudes. For reliable measurement results, every measurement should be traceable with an estimation of measurement uncertainty. In this paper, the Monte-Carlo method is used for uncertainty evaluation of the harmonic components of the measured roundness profile under typical industrial conditions. According to the evaluation, the standard uncertainties for the harmonic amplitudes with the hybrid method are below 0.5 μm for the even harmonics and from 1.5 μm to 2.5 μm for the odd harmonics, when the standard uncertainty for the four probes is 0.3 μm each. The standard uncertainty for roundness deviation is 3.3 μm.     

Effects of flow patterns and salinity on water holdup measurement of oil-water two-phase flow using a conductance method

This research investigates the effects of flow pattern and salinity of oil-water two-phase flow on water holdup measurement using a conductance method. Firstly, vertical upward oil-water two-phase flow experiment is conducted in a 20 mm inner diameter (ID) pipe, in which the salinities of aqueous solutions are set as 151 ppm, 1003 ppm, 2494 ppm and 4991 ppm respectively. Experimental water-cut and mixture velocity are set as 80–100% and 0.0184–0.2576 m/s. In the experiment, three different flow patterns, i.e., dispersed oil-in-water slug flow (D OS/W), dispersed oil-in-water flow (D O/W) and very fine dispersed oil-in-water flow (VFD O/W) are observed and recorded by a high speed camera. Meanwhile, we collect the response of Vertical Multiple Electrode Array (VMEA) conductance sensor excited by a sine voltage signal. The result shows that, for VFD O/W, the water holdup from VMEA sensor shows a satisfied agreement with that of quick closing valve (QCV) method under certain salinities, i.e., 1003 ppm as well as 2494 ppm. For D OS/W flow and D O/W flow characterized by dispersed oil droplets with various sizes, considerable deviations of water holdup between VMEA sensor and QCV method under four kinds of salinity aforementioned are presented. Afterward, according to experimental analysis along with theoretical deviation, it is concluded that the deviation of the measurement system reaches its minimum when reference resistance in the measurement circuit and salinity of the aqueous solution satisfy constraint conditions, and the accuracy of water holdup using the conductance method can be improved through adjusting reference resistance to match the salinity of water phase. Finally, the recurrence plot algorithm is utilized to identify typical flow patterns mentioned above and it shows satisfied results on comprehending the discrepancies among different flow patterns, demonstrating that the recurrence plot algorithm can be effectively applied in flow pattern identification regarding oil-water flows.     

Determining environmental noise measurement uncertainty in the context of the Italian legislative framework

This paper aims to demonstrate the importance of uncertainties in the measurement of environmental noise in the context of Italian legislation on noise pollution focusing the attention on the variability of the measurand as a source of uncertainty and offering a proposal for the evaluation of uncertainty for traffic noise measurement. In particular, drawing on a real traffic noise dataset, firstly outliers are eliminated from the actual noise measurements using an outlier detection algorithm based on K-neighbors distance and then uncertainty range is estimated with the bootstrap-t method. Since the original sequence was Gaussian, this range was compared with the confidence interval of the mean ± standard deviation interval and two intervals were almost coincident.     

High-precision radius measurement of ball indenter

To solve the problem of calibrating the radius of a ball indenter in a hardness tester, a laser confocal radius measurement and calibration method for the ball indenter is proposed without separating the ball from the body of the indenter. The laser confocal radius measurement and calibration method uses the maximum of the confocal axial intensity curve to precisely identify the cat’s eye and confocal position of the test ball indenter. The distance between these two positions is then measured to achieve high-precision radius measurement. The theoretical analyses and experimental results indicate that the radius measurement uncertainty of the ball indenter with a diameter of 1.5875 mm is within 0.12 μm.     

Measurement of highly reflective surface shape using wavelength tuning Fizeau interferometer and polynomial window function

In this study, a 5N − 4 phase shifting algorithm comprising a polynomial window function and a discrete Fourier transform is developed to measure interferometrically the surface shape of a silicon wafer, with suppression of the coupling errors between the higher harmonics and the phase shift error. A new polynomial window function is derived on the basis of the characteristic polynomial theory by locating five multiple roots on the characteristic diagram. The characteristics of the 5N − 4 algorithm are estimated with respect to the Fourier representation in the frequency domain. The phase error of the measurements performed using the 5N − 4 algorithm is discussed and compared with those of measurements obtained using other conventional phase shifting algorithms. Finally, the surface shape of a 4-in. silicon wafer is measured using the 5N − 4 algorithm and a wavelength tuning Fizeau interferometer. The accuracy of the measurement is discussed by comparing the amplitudes of the crosstalk noise calculated by other algorithms. The uncertainty of the entire measurement was 34 nm, better than that of any other conventional phase shifting algorithms.     

A new approach to detection of vortices using ultrasound

The measurement principle of vortex flowmeter is based on von Karman vortex shedding phenomenon. Frequency of vortices, behind the bluff body, is proportional to the mean flow velocity. There are different ways of detection of vortices, and different sensors are used (presser sensors, capacitive sensors, thermo-resistance sensors, ultrasonic sensors, etc.). Proposed method to vortex identification, presented in this paper is based on simultaneous detection of pair of vortices with opposite circulation, by means of two pairs of ultrasonic transducers. A beam of ultrasound, from ultrasonic transmitter to ultrasonic receiver is transmitted perpendicularly to the vortex street. The received ultrasonic signal is amplitude and phase modulated. Frequency of demodulated signal is equal to the frequency of vortices. This technique allows a number of advantages comparing to conventional solutions: reduction, or elimination of noises caused by installation vibration and disturbances in the flow, higher sensor sensitivity, which as a result leads to a possibility of a reduction of the bluff body size, i.e. reduction of the pressure drop on the flow meter, increase of the measurement range in the low flow region, the possibility of redundant operation of the flow meter, reduced measurement uncertainty, instrument technology improvements, improved reliability of the instrument, assured improved statement of complete uncertainty contributions, improved metrology of the equipment as such and calibration procedures that contribute to measuring capabilities etc. For experimental testing a prototype vortex flowmeter of a nominal inner diameter (ID) 50 mm is developed. A cylindrical bluff body for vortex shedding is used. Ultrasonic transducers based on piezo-crystal PZT-5A, inserted in the wall of the vortex meter casing are utilized. The testing of prototype ultrasonic vortex flowmeter is realized on the calibration station on the water. The results at the testing point to the possibility of measuring flow of liquid fluids at velocities less than 0.5 m/s, with an uncertainty better than ±1%.     

Large-scale accelerator alignment using an inclinometer

A precise inclinometer (Talyvel 4) was adopted for evaluating aligning straightness of the first 71 m of the KEK electron/positron injector linear accelerator (linac). The straightness could be evaluated with a standard deviation of less than 49 μm. It is in good agreement with those obtained using a conventional alignment telescope and our laser-based alignment system.Error estimation based on the rules of error propagation shows that shape evaluation with a standard deviation of 0.3 mm for a distance of 500 m can be achieved using the proposed method. It indicates that this method is suitable for evaluating straightness of several hundred meters of linacs with sub-millimeter of accuracy.