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Instrumentation and Measurement, IEEE Transactions on

Issue 5 • Date Oct. 1999

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Displaying Results 1 - 25 of 26
  • Comments on "Influence of voltage contacts on precision measurements of the quantized Hall resistance: an effect of externally injected current"

    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (17 KB)  

    T.P. Chen and H.A. Chua (ibid., vol. 47, pp. 592-4, 1998) proposed a model to explain the influence of the voltage contact resistance R, on the value of the Hall resistance R/sub H/ in high-precision measurements. Their model is based on the observation that the offset current of the null detector of the cryogenic bridge generates a voltage in the contact resistance that induces a deviation of the Hall resistance from its ideal value. Using their model, they give a quantitative interpretation of a set of high-precision measurements made at the Swiss Federal Office of Metrology. The main argument of the paper is as follows: the offset current of the null detector I/sub offset/ will develop an error voltage V/sub d/=I/sub offset/R/sub c/, where R/sub c/ is the contact resistance. We think this argument is wrong. In addition to the contact resistance, the Hall resistance is present between the terminals of the voltmeter and, therefore, the error voltage is given by V/sub d/=I/sub offset/(R/sub c/+2R/sub H/). In this case, RH is multiplied by two because we are comparing two Hall resistances. View full abstract»

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  • A new type of grounding resistance measurement method

    Page(s): 899 - 902
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (92 KB)  

    This paper discusses the measuring methods of grounding resistance. A new measuring method, which uses a higher order spectrum, is suggested. Compared with a power spectrum-based method, the new method can reduce the effect at Gaussian noise, and therefore can measure the grounding resistance more accurately. Simulation and experimental results demonstrate the effectiveness of the new method View full abstract»

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  • Drive to generate digital current for control vertical field in a small Tokamak

    Page(s): 1001 - 1004
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (120 KB)  

    The horizontal position of a small Tokamak plasma has been controlled by a circuit to generate the control vertical field. The circuit must respond quickly to the position signal from a feedback circuit and feed a large current in a short time. We have assembled the circuit to generate a digital current called a drive. The drive includes several units, and each unit is made up of a capacitor, a transistor, a protective resistor and a comparator. We have installed the drive on a small Tokamak, the Hamana-T and obtained satisfactory results. The performance of the drive is described View full abstract»

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  • Self-calibratable voltage transformer testing set

    Page(s): 906 - 908
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (64 KB)  

    The design of a largely self-calibratable voltage transformer testing set (VTTS) is described in which the only components that have a first-order bearing on the instrument's errors are transformer devices working at zero burden. The errors of resistance and capacitance components in the circuit are eliminated by a simple setup procedure which may be carried out each time the VTTS is used. The device described, which could be made up largely from components found in a standards laboratory, should be accurate to within 0.1% of the VTTSs indicated error in both ratio and phase, and would be ideal for checking the accuracy of automatic, digital-read-out VTTSs View full abstract»

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  • A new robust method for six-port reflectometer calibration

    Page(s): 927 - 931
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (112 KB)  

    A new robust method for finding the parameters of Engen's six-port-to-four-port reduction algorithm for six-port reflectometer calibration has been developed. Like other previously published methods, it uses a minimum of five loads with an unknown but constant absolute value of the reflection coefficient and unknown but well-distributed phases. However, the quality of the parameter estimates is improved, especially in noisy environments, by efficiently eliminating cases in which these earlier methods may become ill-conditioned. The new method has been used successfully to calibrate a newly developed six-port reflectometer in GaAs MMIC technology working between 1.3 GHz and 3.0 GHz View full abstract»

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  • An improved lead compensation technique for three-wire resistance temperature detectors

    Page(s): 903 - 905
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (76 KB)  

    An improved lead resistance compensation technique for use with three-wire resistance temperature detectors is presented. The present practice of using the three-wire concept in an unbalanced bridge to provide signal to direct reading instruments produces nearly 1% error for a lead resistance as low as 1 Ω. In contrast, the new method limits the error to below 0.1% with much higher lead wire resistances View full abstract»

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  • Characterization of chromatic dispersion and polarization sensitivity in fiber gratings

    Page(s): 939 - 943
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (88 KB)  

    Fiber gratings have already become key passive components in fiber optic communication systems. We have characterized gratings used in reflection for dispersion compensation and long period gratings used in transmission for gain flattening using a low-loss, low-noise experimental setup having a picometer optical wavelength resolution. Our measurements include reflection or transmission response, group delay and polarization dependent loss. We have scanned the spectrum of our devices using a very narrow linewidth tunable laser. A network analyzer is used for the chromatic dispersion measurements. Time delays corresponding to the design values have been measured within the useful bandwidth of the gratings for dispersion compensation and the devices have been found to have reasonably small ripples that increase in magnitude toward the shorter wavelength range. The long period gratings for gain flattening have very small group delays. Polarization dependent loss has been measured for the first time in these devices. A polarization analyzer was used and Jones matrix analysis was applied to obtain the measurements. The gratings for dispersion compensation have small a polarization dependent loss within their useful bandwidth, while the long period gratings exhibit higher values and a stronger wavelength dependency in the polarization dependent loss View full abstract»

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  • Precision resistors: a review of material characteristics, resistor design, and construction practices

    Page(s): 878 - 883
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (208 KB)  

    An understanding of the properties of resistance materials and of the effects on resistor characteristics of construction practice is necessary to assure optimum application. Reviewed are some of the characteristics of moderate-precision film resistors, the nature of the principal high performance resistance alloys and the design and construction of high-precision resistors. The effects of resistor termination and terminals are also reviewed with emphasis on the requirements necessary to produce four-terminal and series-parallel connections View full abstract»

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  • Transients in reconfigurable digital signal processing systems

    Page(s): 986 - 989
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (84 KB)  

    To solve measurement and control problems, the processing of input data is performed typically by model-based digital signal processing (DSP) systems, which contain a representation of our knowledge about the nature and the actual circumstances of the problem at hand. If the nature or the actual circumstances change, the corresponding model should also be changed. Similarly, if the amount of knowledge about the problem increases due to measurements, an improved model can be suggested which provides better performance. As a consequence, the real-time adaptation or reconfiguration of the DSP system to be applied can hardly be avoided. The transients caused by these adaptations/reconfigurations is investigated. It is shown that for feedback systems, i.e., for infinite impulse response (IIR) filters, these transients are strongly structure-dependent and that the so-called orthogonal filter structures also provide good performance in this respect View full abstract»

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  • Timing characteristics of a Cd1-xZnxTe detector-based X-ray imaging system

    Page(s): 909 - 914
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (100 KB)  

    The timing characteristics of a planar Cd1-xZnx Te sample at each frequency of a scanning square-wave test pattern, has been measured. This study is aimed at evaluating the speed characteristics of a Cd1-xZnxTe detector for X-ray imaging and computed tomographic (CT) applications. The experimental results of this study indicate that the temporal response of a Cd1-xZnxTe detector based X-ray system, improves significantly by optimizing the X-ray tube and detector parameters View full abstract»

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  • A novel noise figure and gain test set for microwave devices

    Page(s): 921 - 926
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    A new instrument for the measurement of noise and gain of microwave devices is presented. It differs from the commercial ones in the accomplishment of the gain measurement and is also useful for measuring mismatched devices such as transistors, The instrument is driven via HP-IB by a PC and a user-friendly virtual panel is designed to perform all the required operations. Also included is the possibility of removing the second-stage noise contribution and correcting various sources of error (source ENR variations, temperature variations, etc.). The test set provides a very good accuracy for both matched and mismatched devices, usually limited by source ENR accuracy and step attenuator repeatability. The performances of the instrument are compared with those offered by commercial instrumentation View full abstract»

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  • A measurement system for on-line estimation of weed coverage

    Page(s): 990 - 994
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (360 KB)  

    This paper describes two different solutions for the estimation of weed coverage. Both measuring systems discriminate the weed from the ground by means of the color difference between the weed and ground and can be used to on-line control tractor sprayers in order to reduce weedkiller use. The solutions differ with respect to the sensor type: one solution is based on a digital camera and a computer that analyzes the images and determines the weed amount, while the other simpler solution makes use of two photodetectors and an analog processing system. The camera-based solution provides an uncertainty of a few percentage, while the photo detector-based one, though extremely cheap, has an uncertainty of about 5% and suffers from changes in light conditions, which can alter the estimations View full abstract»

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  • An improved method for the determination of saturation characteristics of switched reluctance motors

    Page(s): 995 - 1000
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (132 KB)  

    Experimental determination of magnetization characteristics of switched reluctance motors (SRMs) is quite important in their accurate performance prediction. Over the last decade, various experimental procedures have been used to obtain these characteristics. Every evolved new method has its own limitations and constraints. This paper describes an improved, simple and cost effective experimental procedure and an equally simple post-experimental data processing to obtain the flux-linkage-current curves at varying rotor positions of the SRM. The experimental results on a 4 kW, four-phase, 8/6 pole SRMs show the effectiveness of the method and the results compare well with the previously results compare well with the previously published results of similar and higher rating SRM's View full abstract»

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  • Measurement of low oxygen concentrations by phosphorescence lifetime using optical fibers

    Page(s): 949 - 955
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (228 KB)  

    In this paper, a relatively simple, low-cost industrial prototype for measuring low oxygen concentrations in gaseous medium based on phosphorescence lifetime of Al-Ferron in sol-gel probe is presented. The main advantages over other techniques are an excellent sensitivity, precision, selectivity, response time, and facility of maintenance. Fiber optics is used to guide the light. This fact allows one to reach difficult places and to make the measurements from a distance. The design of the system and best ways to maximize the emission maximizing the excitation light from the light source, the optimal distance from the optical fibers to the chemical sensor, and a simple method to filter the response are discussed and verified with the prototype developed. The system allows the detection of oxygen concentrations of 0.005% View full abstract»

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  • Influence of the architecture on ADC error modeling

    Page(s): 956 - 966
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (220 KB)  

    The influence of the architecture on analog-to-digital converter modeling is investigated for the three most widespread architectures: integrating, successive approximations, and flash. The effects of main error sources are analyzed in terms of integral and differential nonlinearity with the aim of setting up a unified error model. Such a model is useful both to economically generate a look-up table for error correction and to quickly produce diagnosis models for fault detection and isolation. Numerical simulations aimed to show the model effectiveness and experimental tests carried out to validate the model are discussed View full abstract»

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  • Precision resistors: a review of the techniques of measurement, advantages, disadvantages, and results

    Page(s): 884 - 888
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    The characteristics of the principal resistance measuring systems developed over the last two centuries are reviewed, Also reviewed is their application to measurement of resistance from μΩ to MΩ. Included in the review are potentiometer systems and their adaptation to computer operation, the Wheatstone bridge, the enhanced Kelvin double-bridge and the current-comparator in both manual and computer operated forms. Methods of establishing ratio from the base 1 Ω reference value throughout the range are discussed. Uncertainties attainable at the highest levels of precision are presented View full abstract»

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  • Behavior of resistors and shunts: with today's high-precision measurement capability and a century of materials experience, what can go wrong?

    Page(s): 889 - 893
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (276 KB)  

    The characteristics of laboratory resistors and high-precision resistors in the principal range, 1 Ω to 10 kΩ, are reviewed. Also reviewed is the history of the shunt and of shunt construction. A method is given for improving the uncertainty of shunts by a factor of five by measuring temperature and providing the resistance-temperature characteristic. Data for high-current shunts using this method are included showing the improvement even in cases where shunt behavior is less than expected. Data are also given for the uncertainty improvement achieved with a common meter type, high-current shunt. The results of efforts to identify the cause of the behavior that went wrong in high-precision shunts are also presented View full abstract»

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  • Narrow-band variable center frequency single-loop and multistage sigma-delta modulators for bandpass signals

    Page(s): 873 - 877
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (120 KB)  

    Oversampled narrow-band single-loop and multistage resonator-based bandpass sigma-delta (Σ-Δ) modulators that can accommodate different passband center to sampling frequency ratios are reported. These tunable bandpass configurations are designed by analytically determining and subsequently verifying through detailed empirical simulations the required compensation hardware to deliver enhanced noise-shaping. It is demonstrated that comparatively superior in-band signal-to-noise ratios and dynamic ranges are attributed to the inclusion of appropriate digital feedforward and feedback compensators within these structures View full abstract»

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  • Using artificial neural networks or Lagrange interpolation to characterize the faults in an analog circuit: an experimental study

    Page(s): 932 - 938
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (140 KB)  

    A technique for diagnosing multiple faults in analog circuits from their impulse response function using a fault dictionary was developed. Dirac impulse input to the circuit was simulated and time domain features of the output response were used to build the dictionary. The test of a real circuit by means of a fault dictionary gives realistic results provided the simulated and measured values are similar. Consequently, the choice of the model used in the simulation is important. The precautions to realize the measurement are described View full abstract»

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  • Vehicle sound signature recognition by frequency vector principal component analysis

    Page(s): 1005 - 1009
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (108 KB)  

    The sound of a working vehicle provides an important clue to the vehicle type. In this paper, we introduce the “eigenfaces method,” originally used in human face recognition, to model the sound frequency distribution features. We show that it can be a simple and reliable acoustic identification method if the training samples can be properly chosen and categorized. We treat the frequency spectrum in a 200 ms time interval (a “frame”) as a vector in a high-dimensional frequency feature space. In this space, we study the vector distribution for each kind of vehicle sound produced under similar working conditions. A collection of typical sound samples is used as the training data set. The mean vector and the most important principal component eigenvectors of the covariance matrix of the zero-mean-adjusted samples together characterize its sound signature. When a new zero-mean-adjusted sample is projected into the principal component eigenvector directions, a small residual vector indicates that the unknown vehicle sound can be well characterized in terms of the training data set View full abstract»

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  • The flat strap sandwich shunt

    Page(s): 894 - 898
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (224 KB)  

    The basic principle of a new shunt, the “flat strap sandwich shunt” (FSSS), which consists of a shielded very thin (to 25 μm) flat strap resistor in the sandwich configuration, a folded flat strap resistor with many rolled together layers, and the proper four-terminal, is illustrated. With such a configuration the distribution of the current density on the strap's section is evaluated to approach that of a theoretical isolated strap. Test results on two implementation prototypes of the FSSS show that both its response time, I2T and its frequency characteristic may be at least the same as the more advanced coaxial shunts. Moreover its construction appears much simpler and less expensive than that of the coaxial shunt. The use of the FSSS for measuring high-impulse and heavy-surge currents or continuous complex currents, as well as in thermal current converters and power transfer, is also illustrated View full abstract»

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  • Evolutionary neural fuzzy systems for noise cancellation in image data

    Page(s): 915 - 920
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2480 KB)  

    A new class of neural fuzzy filters for removing noise from two-dimensional (2-D) measurement data is presented. The proposed approach combines the advantages of the fuzzy and neural paradigms. The network structure is, in fact, specifically designed to exploit the effectiveness of fuzzy reasoning in removing noise without destroying the useful information embedded in the input data. An easy design of new filters is thus obtained because the neuro-fuzzy approach is capable of automatic acquisition of knowledge for a given network structure. The learning method based on genetic algorithms performs an effective training of the network yielding satisfactory results after a few generations. Experimental results show that the proposed approach is very effective also in the presence of data highly corrupted by noise. The neural fuzzy system is largely able to outperform other methods in the literature including state-of-the-art techniques View full abstract»

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  • A rigorous exposition of the LEMMA method for analog and mixed-signal testing

    Page(s): 978 - 985
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (140 KB)  

    The linear error-mechanism modeling technique is an effective tool for testing analog and mixed-signal devices which minimizes the number of measurements required to characterize the static transfer function of a circuit by determining a small number of parameters of a linear error model and then predicting the entire response error. This work focuses on optimizing the linear error-mechanism model algorithm (LEMMA), introducing novel refinements which are shown to improve its performance significantly. We outline the implementation of the algorithm in a tutorial manner, paying due consideration to the underlying theory where required View full abstract»

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  • A fast low-cost solar cell spectral response measurement system with accuracy indicator

    Page(s): 944 - 948
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (116 KB)  

    A novel automated spectral measurement system is presented. Special attention has been focused on the design in order to obtain rapid measurement facilities, minimize hardware and simplify serial communications between the different subsystems involved, resulting in a low-cost measurement system. It is controlled by an HP-9000 computer, through a fully menu-driven interface, and the primary measurement instrument is an HP-4142B modular source-monitor. A new indicator of measurement accuracy is defined, implemented and displayed in real time. This automated system has been employed intensively to study characteristics of different solar cell types in order to optimize their fabrication process. As such this automated measurement system is clearly useful for both research and fabrication View full abstract»

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  • Computed tomography postacquisition data correction for system alignment errors

    Page(s): 972 - 977
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    A critical issue in obtaining high-quality images from a computed tomography system is the mechanical alignment of the data acquisition system. This paper will compare two methods of measuring and correcting errors introduced into second-generation computed tomography data sets from misalignment of the system. Both of these methods use a projection data set from a complete scan of an object as a starting point. One method is an iterative method that looks at residual errors in selected portions of the reconstructed image. The other method requires that the centroids of the projection data coincide with the centroid of the object. It will be shown that the centroid registration algorithm can be used to accurately measure a number of important computed tomography system alignment parameters and is mathematically efficient. The residual error algorithm will be shown to give less satisfactory results View full abstract»

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Aims & Scope

Papers are sought that address innovative solutions to the development and use of electrical and electronic instruments and equipment to measure, monitor and/or record physical phenomena for the purpose of advancing measurement science, methods, functionality and applications.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Prof. Alessandro Ferrero
Dipartimento di Elettrotecnica
Piazza Leonardo da Vinci 32
Politecnico di Milano
Milano 20133 Italy
alessandro.ferrero@polimi.it
Phone: 39-02-2399-3751
Fax: 39-02-2399-3703