This paper presents a modified sine-fitting algorithms which can be used for high-accuracy sampling measurements of complex voltage ratio of sinusoidal signals. The proposed algorithms provide a ...significant reduction in the measurement uncertainty of phase shift when synchronizing the sampler and signal source is impossible.
To assess the reliability of dc energy measurement equipment on-board trains, a setup was developed to characterize current transducers under realistic operating conditions. The operating principle ...is based on a current ratio measurement technique. The reference sensor is a high-precision zero-flux current transducer in combination with a broadband high-precision current shunt. The influence of ac distortion on this reference sensor was found to be within a few parts in 10 6 using an initial version of the setup, in which ac distortion was applied through a separate winding. A revised version of the setup employs a programmable electronic load to apply dynamic currents up to 600 A. The setup was used to characterize a 100 μΩ high-current shunt resistor. The effect of dissipative heating on the dc transresistance error was around 0.03 %, with a settling time of about half an hour. The short-term intrinsic current dependence was also around 0.03 %. The effect of ac distortion was within a few parts in 10 6 . The intrinsic current dependence and the onset of the heating effect were also observed when exposing the sensor to a dynamic current profile that was recorded during a trip between two successive underground train stations on Metro de Madrid. These results demonstrate that the setup described in this paper is very effective for characterizing dc current sensors for practical railway applications. Future work will concentrate on even more demanding current signals, such as chopped signals, and on other types of sensors and measurement systems.
A new method is developed for synchrophasor-based estimation of three-phase transmission line (TL) impedance parameters, applicable for both fully transposed and untransposed TLs. The method is based ...on accurate time-synchronized measurements of the voltage and current phasors at both ends of a TL. The method estimates the line impedance values using a robust estimator with the property that the influence of outliers on the final results is minimized. A robust estimator is chosen as an alternative to well-known ordinary least-squares estimators which are highly sensitive to outliers. The performance of the method has been evaluated using a laboratory setup simulating real power system conditions. The necessary conditions for algorithm convergence as well as the requirements for measurement accuracy have been studied. In addition, this paper describes validation results of the proposed method in real high-voltage power system conditions by measuring voltage and current phasors with two phasor measurement units installed on both terminals of a 400-kV fully transposed overhead TL.
This paper addresses various aspects of optimal phasor measurement unit (PMU) placement problem. We propose a procedure for multistaging of PMU placement in a given time horizon using an integer ...linear programming (ILP) framework. Hitherto, modeling of zero injection constraints had been a challenge due to the intrinsic nonlinearity associated with it. We show that zero injection constraints can also be modeled as linear constraints in an ILP framework. Minimum PMU placement problem has multiple solutions. We propose two indices, viz, BOI and SORI, to further rank these multiple solutions, where BOI is bus observability index giving a measure of number of PMUs observing a given bus and SORI is system observability redundancy index giving sum of all BOI for a system. Results on IEEE 118 bus system have been presented. Results indicate that: (1) optimal phasing of PMUs can be computed efficiently; (2) proposed method of modeling zero injection constraints improve computational performance; and (3) BOI and SORI help in improving the quality of PMU placement.
Classroom Assessment and Educational Measurement explores the ways in which the theory and practice of both educational measurement and the assessment of student learning in classroom settings ...mutually inform one another. Chapters by assessment and measurement experts consider the nature of classroom assessment information, from student achievement to affective and socio-emotional attributes; how teachers interpret and work with assessment results; and emerging issues in assessment such as digital technologies and diversity/inclusion. This book uniquely considers the limitations of applying large-scale educational measurement theory to classroom assessment and the adaptations necessary to make this transfer useful. Researchers, graduate students, industry professionals, and policymakers will come away with an essential understanding of how the classroom assessment context is essential to broadening contemporary educational measurement perspectives.
The combination of a large-field-of-view visual positioning system and a local scanning sensor affords an effective approach to the 3-D measurement of meter-scale objects and has been actively ...investigated by researchers. The calibration of such an integrated measurement system is essential to establish the overall measurement accuracy. This article proposes to calculate the transformation relationship between the local system and the transfer target through the determination of the scales of the combined system. The principle and implementation of this tracking-based combined measurement system are described in this article, as well as the use of the respective scales of the combined system to establish a model of the applicable geometrical relationships. The Kronecker product was used to solve the model equations, after which homogenous transformation matrix optimization was performed. An error model of the camera-based measurement system was also established based on a combination of the image distortion and the working volume. The 2-D and 3-D errors of the local and global sensors were further quantitatively simulated and visualized to demonstrate the calibration accuracy. Standard plane and complex large object measurement experiments were performed to verify the accuracy of the proposed measurement system and its use for the reconstruction of a large shape.
The ever-growing complexity of radiating systems asks for always more challenging radiation pattern characterizations requiring time consuming field acquisitions and high-cost facilities. ...Consequently phaseless, or magnitude-only, measurements have recently regained of interest as they prevent the tedious and difficult task of phase acquisition. Consequently, it allows the use of cheaper or more versatile measurement setups like drone measurements or easier high-frequency measurements. However, the difficulty is shifted to the notoriously difficult resolution of the phase retrieval problem, which instability is commonly mitigated by the acquisition of a large number of phaseless field samples. A procedure enabling a reliable and accurate phaseless antenna measurement from a reduced number of spherical NF samples based on the two scan technique is proposed. Its efficiency and stability, that relies on the systematic determination of a good starting point, is validated by representative simulations and experimental cases performed on various antenna structures.
On the Estimation of Angle Rate in Radar Nanzer, Jeffrey A.; Sharp, Matthew D.
IEEE transactions on antennas and propagation,
2017-March, 2017-3-00, Volume:
65, Issue:
3
Journal Article
Peer reviewed
The direct measurement of the angle rate of moving objects using a radar with a spatially diverse electric field pattern, a measurement analogous to the measurement of the range rate of a moving ...objects, represents, along with the measurements of range, range rate, and angle, a fourth basic radar measurement. Recently introduced and experimentally demonstrated, the theoretical accuracy of the direct measurement of angle rate is derived in this paper, and it is compared to the measurements of range, range rate, and angle in the context of the optimal signal forms for the best measurement accuracy. Signal forms achieving optimal accuracy for each measurement are discussed; example implementations of high-accuracy measurements are compared to the optimal forms; and the limitations of simultaneous measurements of pairs of measurements are derived. Combining the angle rate measurement with the three other standard radar measurements may provide future radar systems the capability to simultaneously and instantaneously measure the position and 3-D trajectory of moving objects without compromising the accuracy of any individual measurement.
Despite developments in research and practice on using examinee response process data in assessment design, the use of such data in test validation is rare. Validation of Score Meaning in the Next ...Generation of Assessments Using Response Processes highlights the importance of validity evidence based on response processes and provides guidance to measurement researchers and practitioners in creating and using such evidence as a regular part of the assessment validation process. Response processes refer to approaches and behaviors of examinees when they interpret assessment situations and formulate and generate solutions as revealed through verbalizations, eye movements, response times, or computer clicks. Such response process data can provide information about the extent to which items and tasks engage examinees in the intended ways. With contributions from the top researchers in the field of assessment, this volume includes chapters that focus on methodological issues and on applications across multiple contexts of assessment interpretation and use. In Part I of this book, contributors discuss the framing of validity as an evidence-based argument for the interpretation of the meaning of test scores, the specifics of different methods of response process data collection and analysis, and the use of response process data relative to issues of validation as highlighted in the joint standards on testing. In Part II, chapter authors offer examples that illustrate the use of response process data in assessment validation. These cases are provided specifically to address issues related to the analysis and interpretation of performance on assessments of complex cognition, assessments designed to inform classroom learning and instruction, and assessments intended for students with varying cultural and linguistic backgrounds.
This contribution focuses on the nondestructive evaluation of the thickness of metallic plates, by means of eddy-current testing. Specifically, we present a method for reducing/optimizing the ...measurement time for the approach presented in (Yin and Peyton, 2007), while keeping a high accuracy suitable for industrial applications. In (Yin and Peyton, 2007), the key feature for estimating the thickness of plates is the value of the frequency where a proper quantity achieves its minimum value. To get a proper accuracy in measuring the thickness of the plate, this minimum needs to be located in an accurate manner. In turns, this requires "many" measurements at different frequencies, which make the approach time-consuming and not suitable for almost real-time applications, as those of interest for industry. The proposed patent pending strategy combines a multisine approach to collect the data onto a proper set of frequencies, plus proper techniques for interpolating the data at all the frequencies required to locate accurately the minimum of the response. The combination of the multisine to allocate efficiently the measurement frequencies with the data interpolation results in a reduction of the number of required measurements and, in ultimate analysis, of the overall measurement time. Specifically, the measurement time for a typical situation was reduced of a factor of about 4 (from 13 to 2.66 s) with the same accuracy level of the order of 3%. Finally, we highlight that both design and testing of the new measurement method were carried out by combining numerical simulations and experimental results.
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