Digital Measurement Method Research Articles

A Novel Method for Phase Noise Measurement Based on Cyclic Complementary Autocorrelation

A novel digital signal processing-based method for phase noise measurement on sinusoidal signals is proposed. The method obtains the power spectral density of the phase noise by Fourier transforming its autocorrelation function. The autocorrelation function of the phase noise is in turn derived from the cyclic complementary autocorrelation function of the analytical version of the sinusoidal signal under test. The method proves that, taking advantage of the cyclostationarity properties of the signal under test, it is possible to improve the sensitivity in phase noise measurements by diminishing the effects of the instrumentation noise, which mainly limits the performance of the majority of the digital processing-based approaches.

Accuracy improvement of the stochastic digital electrical energy meter

Abstract The paper describes the problem and a solution for the elimination of the systematic error in a stochastic flash ADC caused by the offset present in fast voltage comparators, when measuring voltage RMS and active power and energy using the stochastic digital measurement method. By the means of simple periodical cross-switching of inverting and non-inverting inputs of used comparators and inverting their digital outputs, it is possible to suppress offset induced error for over 80 dB. Main condition for the method is that input signals (one for voltage RMS measurement, two for power and energy measurements) are stationary during at least two (or even number) of signal cycles. A prototype of a stochastic energy meter was built. It has the offset suppression method implemented, based on the solution proposed in the paper. The prototype was used for measurements in a laboratory, in an industrial plant and on a large power load. The measurement results confirm high accuracy of the instrument and validity of its aforementioned condition. The stochastic digital electrical energy meter prototype has 0.13% accuracy while the stochastic measurement instrument in its core has 0.007% accuracy. High precision and high accuracy of the stochastic instrument enables it to be used as a reference meter for calibration of energy meters at the national level. Full measurement results are presented.

A new digital pulse processing method for 2πα and 2πβ emitter measurement

Digital pulse processing has developed rapidly during recent years. Moreover, it has been widely applied in many fields. In this study, we introduce a digital pulse processing method for 2πα and 2πβ emitter measurement. Our digital pulse processing method for 2πα and 2πβ emitter measurement is comprised of a field-programmable gate-array-based acquisition card and a pulse-height analysis routine. We established two channels (one for the α emitter and one for the β emitter) on an acquisition board using an analog-to-digital converter with a 16-bit resolution at a speed of 100 million samples per second. In this study, we used captured and stored data to analyze emission rate counts and spectrums. The method we established takes into account noise cancelation, dead-time correction, background subtraction, and zero-energy extrapolation. We carefully designed control procedures in order to simplify pulse-width fitting and threshold-level setting. We transmitted data and commands through a universal serial bus between the acquisition board and the computer. The results of our tests prove that our method performs well in pulse reconstruction fidelity and amplitude measurement accuracy. Compared with the current standard method for measuring 2πα and 2πβ emission rates, our system demonstrates excellent precision in emission rate counting.

Validation of Xanthophyll Levels in Catfish Fillets Using Digital Photography

Catfish fillets with yellow coloration have become a prevalent problem for the catfish industry. This problem is due to the unacceptability in the market because the shift in fillet color is considered of lower quality by the consumers. To help the catfish industry better understand the yellow coloration of catfish fillet, a digital photography measurement method was developed to evaluate the yellowness. Sixty catfish fillets with a range of degrees of visible yellowness were taken directly from the processing line. The fillets were photographed in a light box with a digital camera. The photos were calibrated with the X-Rite ColorChecker standardized color target. CIELAB readings of the fillet photos were recorded, and the b* value was used to indicate the yellowness of catfish fillets. The xanthophyll levels of fillets were analyzed with high performance liquid chromatography. The actual xanthophyll level in catfish fillet was calculated as the sum of lutein, zeaxanthin, and alloxanthin. A linear correlation was found between the LAB b* values and xanthophyll levels of the 60 catfish fillets.

Shrinkage characteristics studies on conventional sintered zirconia toughened alumina using computed tomography imaging technique

Shrinkage is an important issue during sintering of ceramics as it affects the structural and mechanical properties. In the current work, the shrinkage characteristics of sintered zirconia toughened alumina (ZTA) compact produced by conventional powder forming process was investigated by using computed tomography imaging technique. The effect of process parameters such as weight percentage of zirconia added to toughened alumina, compaction pressure, and sintering temperature on ZTA was studied. The Box–Behnken technique in response surface methodology was used to develop the experimental design to analyze the shrinkage phenomena. The sintered samples were subjected to computed tomography scan and analyzed by using MIMICS Software wherein the three dimensional shrinkage of the ZTA composites was done. The mathematical regression model relating powder forming process parameters to the shrinkage was developed. It was observed that due to the effect of gravity, shrinkage is found to be 20% in the top for 1600°C sintered sample. From the study shrinkage of the sintered ZTA was influenced by the sintering temperature. Being a non-contact type digital measurement method the odds of error created by instrument or human was avoided. Shrinkage of three directional complex shapes can also be identified effectively with the help of solid modeling packages.

Comparison of a new laser beam wound camera and a digital photoplanimetry-based method for wound measurement in horses

The aim of this study was to compare the accuracy, precision, inter- and intra-operator reliability of a new laser beam (LB) wound camera and a digital photoplanimetry-based (DPB) method for measuring the dimensions of equine wounds. Forty-one wounds were created on equine cadavers. The area, circumference, maximum depth and volume of each wound were measured four times with both techniques by two operators. A silicone cast was made of each wound and served as the reference standard to measure the wound dimensions.The DPB method had a higher accuracy and precision in determining the wound volume compared with the LB camera, which had a higher accuracy in determining the wound area and maximum depth and better precision in determining the area and circumference. The LB camera also had a significantly higher overall inter-operator reliability for measuring the wound area, circumference and volume. In contrast, the DPB method had poor intra-operator reliability for the wound circumference. The LB camera was more user-friendly than the DPB method.The LB wound camera is recommended as the better objective method to assess the dimensions of wounds in horses, despite its poorer performance for the measurement of wound volume. However, if the wound measurements are performed by one operator on cadavers or animals under general anaesthesia, the DPB method is a less expensive and valid alternative.

All-digital thermal distribution measurement on field programmable gate array using ring oscillators

In this paper, a digital method for transient temperature distribution measurement of field programmable gate array (FPGA)-based systems is proposed. The smart thermal sensors used rely on correspondence between the delay and temperature in a ring oscillator. The tested temperature was converted into a time signal with a thermally-sensitive width. The output frequency is read out by a counter with a scan path, and then, transited to PC by a Universal Serial Bus (USB) interface. We capture the infrared images of the FPGA chip by infrared camera. The images were compared with the thermal map of the die constructed using an array of sensors. The tested temperature error varies by less than 1.6°C in the range from 20°C to 90°C, and the maximum sampling rate is 330Hz.

Digital image processing method for static balance measurement of incomplete spherical rotor with air suspension

Measurement and calibration of mass imbalance for rotors are often indispensible as mass imbalance will cause undesired vibration and present serious problems accordingly. In this study, a new method based on digital image processing (DIP) to measure the mass imbalance of a special rotor with air suspension is introduced. By hunting the trace of tilt angle through several identification points on the rotor by DIP, the corresponding oscillating period will be determined, which in turn contributes to the calculation of mass imbalance. Two-dimensional monochrome charge-coupled device (CCD) and peripheral component interconnect (PCI) image board are applied in the experiment to capture the rotor's image, and several user interfaces are developed for image processing and curve fitting as well. Besides, the system error analysis and the comparison of experimental results with that of other related work are provided, which prove the effectiveness and accuracy of this DIP method.

Novel scanning electron microscope bulge test technique integrated with loading function.

Membranes and film-on-substrate structures are critical elements for some devices in electronics industry and for Micro Electro Mechanical Systems devices. These structures are normally at the scale of micrometer or even nanometer. Thus, the measurement for the mechanical property of these membranes poses a challenge over the conventional measurements at macro-scales. In this study, a novel bulge test method is presented for the evaluation of mechanical property of micro thin membranes. Three aspects are discussed in the study: (a) A novel bulge test with a Scanning Electron Microscope system realizing the function of loading and measuring simultaneously; (b) a simplified Digital Image Correlation method for a height measurement; and (c) an imaging distortion correction by the introduction of a scanning Moiré method. Combined with the above techniques, biaxial modulus as well as Young's modulus of the polyimide film can be determined. Besides, a standard tensile test is conducted as an auxiliary experiment to validate the feasibility of the proposed method.

이미지 상관법을 이용한 3 점 굽힘 시험 계측 프로그램 개발 관한 연구

Machine parts and structures of a change in the displacement and strain can be evaluated safety is one of the important factors. Typically the strain gauge has been employed to measure the displacement and strain. However, this contact-type measurement method has disadvantages that are not measured under condition of specific object shape, surface roughness and temperature. In particularly, 3 point bending and 4 point bending test not use strain gauge. So its test used cross head displacement and deflect meter. Digital Image Correlation measurement methods have many advantages. It is non contact-type measurement method to measure the object displacements and strain. In addition, it is possible to measure the Map of full field displacements and strain. In this paper, measured the 3 point bending deflection using the Digital Image Correlation methods. In order to secure the reliability, Digital Image Correlation method and universal test machine were compared.

High-temperature digital image correlation method for full-field deformation measurement captured with filters at 2600°C using spraying to form speckle patterns

A method is presented for obtaining good images of a sprayed speckle pattern on specimen surfaces at high temperatures, suitable for strain measurement, by digital image correlation (DIC) using plasma spray for speckle preparation in which a bandpass filter, neutral density filters, and a linear polarizing filter are used to reduce intensity and noise in images. This is accomplished by speckle preparation through the use of plasma spray and suppression of black-body radiation through the use of filters. By using plasma spray for speckle preparation and the filters for image acquisition, the method was demonstrated to be capable of providing accurate DIC measurements up to 2600°C. The full-field stretching deformation of the specimen was determined using the DIC technique. Experimental results indicate that the proposed high-temperature DIC method is easy to implement and can be applied to practical, full-field, high-temperature deformation measurements with high accuracy.

The Relationship Among Foot Posture, Core and Lower Extremity Muscle Function, and Postural Stability

Identification of impaired balance as a risk factor for lower extremity injury regardless of injury history has led to subsequent investigation of variables that may adversely affect balance in healthy individuals. To investigate the relationship among core and lower extremity muscle function, foot posture, and balance. Descriptive laboratory study. Musculoskeletal injury biomechanics laboratory. A total of 108 individuals (40 men, 68 women; age = 22.8 ± 4.7 years, height = 168.5 ± 10.4 cm, mass = 69.9 ± 13.3 kg) participated in the study. Core endurance was assessed during 1 time-to-failure trial, and isometric hip and ankle strength were assessed using a handheld dynamometer and isokinetic dynamometer, respectively. Foot structure was quantified using the digital photographic measurement method. Single-limb-stance time to boundary was assessed using a force plate during an eyes-closed condition. Hierarchical multiple regression analyses were performed to predict balance using lower extremity strength, foot posture, and core endurance. Foot posture (β = -0.22, P = .03) and ankle-inversion strength (β = -0.29, P = .006) predicted mediolateral balance. Increasing arch posture and ankle-inversion strength were associated with decreased mediolateral single-limb-stance balance. Increasing arch height was associated with decreased mediolateral control of single-limb stance. The relationship between time to boundary and injury risk, however, has not been explored. Therefore, the relationship between increasing arch height and injury due to postural instability cannot be determined from this study. If authors of future prospective studies identify a relationship between decreased time to boundary and increased injury risk, foot structure may be an important variable to assess during preparticipation physical examinations. The relationship between increasing ankle-inversion strength and decreased balance may require additional study to further elucidate the relationship between ankle strength and balance.

Relay-style Digital Speed Measurement Method and Dynamic Position Subdivision Method

This paper proposes an advanced M/T method called Relay-style Digital Speed Measurement Method. Its speed measurement is triggered by encoder pulse signals, which simplifies the complexity of processing incapability of synchronization in the classical method, and it makes actual sampling point always occur before the periodic sampling point in relay-style, which achieves the continuous dynamic iterative measurement with high accuracy in a wide speed range. Through counting the overflow pulses of time counter by software, the minimally measurable speed can be effectively extended to an extremely low level without adding any hardware. In addition, by utilizing the information in speed measurement and subdividing dynamic position by time according to its corresponding relationship with time, Dynamic Position Subdivision Method is achieved to improve the feedback resolution of dynamic position. Finally, the experimental results show that Relay-style Digital Speed Measurement Method can obtain high accuracy than classical method in a wide speed range even though at a very low speed Dynamic Position Subdivision Method is helpful to reduce the fluctuations of the position control.

Standardisation of 64Cu using a software coincidence counting system

The activity of the radionuclide 64Cu was determined by the efficiency extrapolation method applied to 4π(PC)−γ coincidence counting. The standardisation was performed by software coincidence counting—a digital method for primary activity measurement that simplifies the setting of optimal coincidence parameters. The γ-ray-energy window, characterised by identical gamma detection efficiency related to the sum of EC and to the sum of beta decay branches, was found. This setting ensured a linear and zero slope extrapolation curve.

Influence of Signal Stationarity on Digital Stochastic Measurement Implementation

The paper presents the influence of signal stationarity on digital stochastic measurement method implementation. The implementation method is based on stochastic voltage generators, analog adders, low resolution A/D converter, and multipliers and accumulators implemented by Field-Programmable Gate Array (FPGA). The characteristic of first implementations of digital stochastic measurement was the measurement of stationary signal harmonics over the constant measurement period. Later, digital stochastic measurement was extended and used also when it was necessary to measure time-series of non-stationary signal over the variable measurement time. The result of measurement is the set of harmonics, which is, in the case of non-stationary signals, the input for calculating digital values of signal in time domain. A theoretical approach to determine measurement uncertainty is presented and the accuracy trends with varying signal-to-noise ratio (SNR) are analyzed. Noisy brain potentials (spontaneous and non-spontaneous) are selected as an example of real non-stationary signal and its digital stochastic measurement is tested by simulations and experiments. Tests were performed without noise and with adding noise with SNR values of 10dB, 0dB and -10dB. The results of simulations and experiments are compared versus theory calculations, and comparasion confirms the theory.

Three-dimensional deformation of orthodontic brackets

Braces are used by orthodontists to correct the misalignment of teeth in the mouth. Archwire rotation is a particular procedure used to correct tooth inclination. Wire rotation can result in deformation to the orthodontic brackets, and an orthodontic torque simulator has been designed to examine this wire–bracket interaction. An optical technique has been employed to measure the deformation due to size and geometric constraints of the orthodontic brackets. Images of orthodontic brackets are collected using a stereo microscope and two charge-coupled device cameras, and deformation of orthodontic brackets is measured using a three-dimensional digital image correlation technique. The three-dimensional deformation of orthodontic brackets will be evaluated. The repeatability of the three-dimensional digital image correlation measurement method was evaluated by performing 30 archwire rotation tests using the same bracket and archwire. Finally, five Damon 3MX and five In-Ovation R self-ligating brackets will be compared using this technique to demonstrate the effect of archwire rotation on bracket design.

Digital Holographic setup for Measurement of Asymmetric Temperature Field and Tomographic Reconstruction

This paper presents a digital holographic multidirectional interferometric method for measurement of periodic asymmetric temperature fields. This method uses a modified Twymann-Green setup having double sensitivity. The setup employs one precisely synchronized and triggered CCD camera with a measured coherent phenomenon. That allows a large number of the phenomenon’s different projections capturing which are used for 3D tomographic reconstruction..

General temperature field measurement by digital holography

This paper presents a digital holographic method for measurement of periodic asymmetric temperature fields. The method is based on a modified Twyman-Green setup having double sensitivity. For measurement only one precisely synchronized and triggered digital camera is used. The periodicity and self-similarity of each cycle of the measured phenomenon combined with the precisely synchronized camera capture allow one to obtain data later used for three-dimensional (3D) measurement. The reconstruction of 3D temperature field is based on tomographic approach.

Fundamental limits on the digital phase measurement method based on cross-correlation analysis

Ultra-precision phase measurement is a key technology for state-of-the-art laser interferometry. In this paper we present a fully digital phase measurement method based on cross-correlation analysis, and analyze the measurement errors caused by sampling quantization, intrinsic white noise and non-integral-cycle sampling. The last error source results in a cyclic error that has not been reported ever. We used a high-performance data acquisition system to carry out the cross-correlation-based phase measurement, and obtained a noise level of 1.2 × 10(-6) rad/Hz(1/2)[commercial at]1 Hz. Moreover, the cyclic phase error of about 10(-2) rad/Hz(1/2), caused by non-integral-cycle sampling, had been observed. In order to demonstrate the application of this precision phase measurement method, an ultra-precision heterodyne laser interferometer, consisting of digital phase measurement system and ultra-stable optical bench, was constructed for displacement measurement. The experimental results showed that a measurement resolution of 63 pm had been achieved.

Quantitative measurement of filament ruptures of a multi-filament AR-glass yarn embedded in concrete

This paper presents a new digital image analysis method for quantitative and online measurement of filament ruptures of a multi-filament AR-glass yarn embedded in concrete during pullout loading. The proposed method was developed based on an existing test method for determination of filament ruptures occurring during the loading called failure investigation using light transmitting (FILT) property test, which uses light transmitting property of AR-glass fibers. Artificial light is exposed on the glass filaments from one side of the specimen. On the opposite side, a charge-coupled device (CCD) camera with an optical microscope records the lighted filament cross-sections in the yarn. To detect filament ruptures during pullout loading, the light intensity time history of every individual filament of the yarn was investigated by a digital image analysis method. The number of broken filaments was also investigated by acoustic emission (AE) analysis simultaneously and the results were compared. Test results showed that the light transmitting property of AR-glass can be used to identify filament ruptures and it is possible to determine the failure of the filaments during pullout in the cross-section quantitatively by the improved FILT test.