IEEE-USA E-Books

• Fill level measurement in a closed vessel by monitoring pressure variations due to thermodynamic equilibrium perturbation

  This paper presents investigations on how to determine the fill level/volume of a fluid in a vessel by means of evaluating the characteristics of pressure changes in the vapor pressure. A laboratory measurement setup is proposed and measurement results for water are presented. Observations and findings may be used for fill level measurement in tanks containing cryogenic fluids without major modifications.

• Comparative magnetic field measurements for homogeneity adjustment of magnetic resonance imaging equipments

  The goal of this paper is to demonstrate three methods for static magnetic field measurement on a whole body magnetic resonance imager. The measured data are serving for computation of feeding currents of correcting coils for the static magnetic field used in NMR imaging. The methods suggest to measure the magnetic field in selected points twice: 1. correcting coils are switched off and 2. measurement of magnetic field changes caused by switching on the feeding current of particular correcting coil in each of selected measuring points. Measurements are realized using: magnetometer based on Hall effect, NMR point magnetometer and gradient echo imaging method applied to circular test tubes. All three measurements measure magnetic field on a circle (12 measuring points) and one point in the center. A set of linear equations, determination of a target function and optimization computations are procedures that provide optimal values of currents for correcting coils. Results of all three methods are compared and discussed. The proposed method is suitable for periodic testing and magnet in homogeneities correction for MRI magnets.

• Generalized phase measurement and processing with application in the time-frequency measurement control and link

  Traditional phase measurement is limited by the identical nominal frequencies of two compared signals. In a lot of applications, there are higher requirements not only on measurement accuracy, but also on the frequency range of compared signals. After years of exploration and efforts, we have discovered some concepts and characteristics which can reflect mutual phase relationship among different frequency signals, such as Least Common Multiple Period, Phase Difference Quantization Step, Equivalent Phase Comparison Frequency, and the continuous phase group characteristics with the least common multiple period (as the time interval and the quantization step phenomenon that the phase difference of the two different frequency signals will change according to a specific value in one least common multiple period). In the process of experiments, we have discovered ambiguity zone edge effects and measurement method of periodic signal parameter quantization error elimination. We achieved precise frequency source synchronization and link, phase processing and measurement between completely different frequency signals with complex relationship. Through updating concepts, we move phase comparison and processing beyond identical frequency signals and extend to arbitrary frequency signals. Major applications include measurement of transient stability, phase noise measurement, edge effects for accurate frequency measurement method of Serial and Parallel. These breakthroughs promote rapid development in the area of measurement and instrument, and some difficult research problems have been solved.

• Low distortion power amplifier for battery measurement systems

  Typically a battery is the best choice as electrical energy storage for mobile applications. Design and optimization of the system components are based on simulation of the whole system needing an adequate battery model. For the parameter identification measurement data is needed. This work presents a prototype of a measurement system that is capable of testing and obtaining the required measurements from batteries with capacities from a few mAh for embedded devices to several hundred Ah for hybrid electric vehicles and electric vehicles.

• Fast, high accuracy, freely programmable single cell battery measurement system

  Batteries are the most practical energy storage for mobile electrical devices. Aiming for more efficient battery systems results in new challenges for developers and scientists. Equipping a mobile device with an adequate battery typically requires an accurate model about the battery's behavior. To establish good models, precision measurements are necessary. In this paper we describe the development and evaluation of a fast, highly accurate and freely programmable battery measurement system. The system consists of a current source which can sink and source currents up to 32 A in a frequency range from DC to 20 kHz, combined with a high resolution measurement of current, voltage and temperature.

• Measurement Capability of Scanning Microwave Microscopy: Measurement Sensitivity Versus Accuracy

  Here, we investigate the measurement capability of a near-field scanning microwave microscope (SMM) using an atomic force microscope with several types of matching circuits for the characterization of high-permittivity dielectric materials. A fixed impedance matching circuit is generally used in SMM products. In this paper, we propose two types of passive interferometer circuits for the application of SMM systems in laboratories. Both systems are useful for operators without knowledge of microwave measurements; however, they are somewhat limited in their measurement ranges and accuracy when performing high-reflection measurements in the characterization of high- permittivity dielectric materials. Thus, we investigate the stability and the accuracy of SMMs with both setups for measurements on high-permittivity dielectric materials; here, we show that an SMM with an interferometric circuit can achieve a low data distribution and a high-dynamic range, and is, therefore, capable of quantitatively characterizing high-permittivity dielectric materials over frequencies higher than approximately 8 GHz.

• The NIST project for the electronic realization of the kilogram

  The project Electronic Realization of the Kilogram has rebuilt the National Institute of Standards and Technology (NIST) watt balance, which has been fully operational for nine months. Short-term noise is at an all-time low with overnight runs exhibiting standard deviations of parts in 10/sup 8/. Recent improvements are discussed that have led to this enhanced performance, as are several significant error tests. Present watt results (i.e., Planck's constant) are now within 1 /spl mu/W/W of CODATA values, but error checking to report a more precise value has not been completed.

• Laser Confocal Interference Multi-Parameter Measurement Method for Spherical Lens

  This letter proposes a new, comprehensive laser confocal interference multi- parameter measurement method (CIMPM) to improve the measurement accuracy and efficiency for the multiple parameters of a spherical lens. By integrating laser confocal and sphere interference measurement techniques, the proposed CIMPM uses the laser confocal focusing technique to measure the radius, thickness, and refractivity of a spherical lens, and uses laser interference measurement technique to measure the surface figure. So, this technique achieves high accuracy comprehensive multi-parameter measurements of a spherical lens on a single instrument. Experiments indicate that the proposed CIMPM can achieve a measurement accuracy of 9 ppm for the radius, 3.2.×10-4for the thickness, 1.6.×10-4for the refractivity, and a peak to valley of λ/20 for the surface figure.

• Precision Measurement System for the Calibration of Phasor Measurement Units

  Phasor measurement units (PMUs) are used for monitoring, protection, and control of smart grids. Characterization of PMUs to national standards of measurement is important to assure reliability and consistency of PMUs across the industry and is required by documentary standards. At the National Measurement Institute, Australia, we have developed a calibration system to provide some calibration points for the characterization of PMUs under steady- state conditions that can be compatible with standard tests. This paper describes the operation and calibration of the system with emphasis on traceability to national standards of measurement.

• Brief overview of methods for measurement uncertainty analysis: GUM uncertainty framework, Monte Carlo method, characteristic function approach

  The basic working tool in measurement uncertainty analysis, as advocated in recent discussions related to the possible revision of the Guide to the expression of uncertainty in measurement (GUM), and in particular by its Supplements, is the state-of-knowledge distribution about the quantity derived based on the currently available information. The GUM uncertainty framework (GUF) provides a method for assessing uncertainty based on the law of propagation of uncertainty and the characterization of the output quantity by a Gaussian distribution or a scaled and shifted t-distribution. Supplement 1 is concerned with the propagation of probability distributions through a measurement model as a basis for the evaluation of measurement uncertainty, and its implementation by a Monte Carlo method (MCM). Supplement 2 describes a generalization of MCM to obtain a discrete representation of the joint probability distribution for the output quantities of a multivariate model. An alternative tool to form the state-of-knowledge probability distribution of the (scalar) output quantity in linear measurement model, based on the numerical inversion of its characteristic function, which is defined as a Fourier transform of its PDF. Here we present brief overview and some remarks on applicability of these approaches for uncertainty analysis, with emphasized focus on the Characteristic function approach (CFA).