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Instrumentation and Measurement Technology Conference, 1991. IMTC-91. Conference Record., 8th IEEE

Date 14-16 May 1991

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Displaying Results 1 - 25 of 121
  • Conference Record. IEEE Instrumentation and Measurement Technology Conference (Cat. No.91CH2940-5)

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    Freely Available from IEEE
  • Control of particulate magnetic coating properties using dispersion quality measurement

    Page(s): 391 - 397
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    A description is given of the use of a rheomagnetic instrument which provides an indirect measurement of the dispersion quality of a magnetic ink suspension used for coating application in the manufacture of magnetic disks. The instrument was designed, tested, and put on a pilot line to characterize the relationships between the dispersion quality measurement and functional characteristics of the magnetic disks. The results of tests performed during pilot production suggest that it is possible to predict some of the disk coating properties based on the dispersion quality of the magnetic particle suspension measured prior to coating. The results yielded a qualitative correlation between the in-situ measurements made on the magnetic particle suspension at the coater with the surface roughness due to flocs, the on-disk orientation ratio, and the signal to noise ratio. The instrument then can be used in a feedforward process control scheme to monitor and control the dispersion quality of the coating suspension to maintain the uniformity of magnetic and wear properties of the magnetic disks View full abstract»

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  • Digital time of flight measurement for ultrasonic sensors

    Page(s): 198 - 201
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    Ultrasonic sensor measurements are mostly based on the determination of the time of flight (TOF). The authors present the development of a digital algorithm for pulse-echo measurement applications, based on the use of a cross-correlation function to determine the TOF. Some experimental results are presented, and the possibility of realizing a low-cost real-time measurement system is considered View full abstract»

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  • Design concepts of instruments for vector parameter identification

    Page(s): 347 - 352
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    The design concepts for phase-sensitive measuring instruments, which are based on two-phase synchronous detection and known as vector analyzers, are proposed. The main idea of the design is to use the advantages of both analog and digital signal processing methods by combining the synchronous detection and averaging procedures with the integrating analog-to-digital and functional digital-to-analog conversion principles. The reference channel of the vector analyzer is built up on the basis of the adaptive third-order phase-locked loop (PLL) View full abstract»

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  • Enhanced vibration monitoring using parametric modelling technique

    Page(s): 2 - 5
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    A parametric modeling technique has been applied to the predictive maintenance of rotating machinery. The case, which is explained in detail, was taken from an experiment in which a one-step gearbox was run at about 150% of nominal load until failure occurred. During the experiment, vibration signals from the gearbox were measured. The novelty of this work is to analyze the residual signal obtained by computing the difference between the predicted and measured signal. A parametric modeling technique called autoregressive modeling is utilized in the prediction procedure. The analysis of the residual signal proved to be successful; the failure could be predicted easier and earlier than using traditional fast Fourier transform (FFT)-based methods View full abstract»

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  • Detection and classification of buried dielectric anomalies using a separated aperture sensor and a neural network discriminator

    Page(s): 432 - 439
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    The problem of detection and classification of buried dielectric anomalies using artificial neural networks was considered. Several methods for training and data representation were developed to study the trainability and generalization capabilities of the networks. The effect of the architectural variation of the network performance was also studied. The principal component method was used to reduce the volume of the data and also the dimension of the weight space. Simulation results on two types of targets were obtained which indicated superior detection and classification performance when compared with the conventional methods View full abstract»

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  • On the development of a rule based expert system for multichannel spectral estimation

    Page(s): 425 - 431
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    The development of a rule-based expert system for multichannel spectral estimation is presented. Expert system specifications, a knowledge acquisition framework, and the selection of a control architecture are discussed. Three control architectures are described: the metarule architecture, the metaknowledge architecture, and the blackboard architecture View full abstract»

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  • On identification of dimensional function of many variables

    Page(s): 209 - 212
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    A method for identification of dimensional functions of many variables is described. It is based on the combined use of dimensional analysis and statistical methods. The identified function is transformed into an equivalent dimensionless function which has a smaller number of variables, and, by using the preliminary measurements, the dimensionless function is decomposed into a product of functions of single variables. These are identified in succession and the final form of the dimension function is then constructed View full abstract»

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  • A review on the development of piezoelectric composites for underwater acoustic transducer applications

    Page(s): 410 - 413
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    For future sonar transducer applications that emphasize the detection of acoustical signals in a hydrostatic mode, new piezoelectric composite materials have been developed. Ceramic-polymer composites having `1-3' and `0-3' connectivity patterns are shown to exhibit much higher sensitivities than conventional PZT ceramics. Glass-ceramic composites are free of aging and have potential applications in standard transducers View full abstract»

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  • Experimental determination of stress in magnetic recording thin film disks

    Page(s): 398 - 404
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    An experimental program is described to help understand and explain the stress state in Cr and CoCrPt thin films sputtered on ceramic (canasite) substrates. Thin film magnetic recording disk substrates are used with production process equipment. A measurement technique is developed. The effect of Cr thickness and sputter preheat on stress in the Cr layer is determined. Stresses in equal thickness Cr and CoCrPt films on canasite are compared. Repeatability of stress levels in films deposited several weeks apart is examined. Average stress immediately after deposition and after several weeks is determined to look for time-dependent effects. A factorial experiment explores the process space of preheat, Cr thickness, and CoCrPt thickness with average film stress as the output variable. After making several assumptions, stress in the CoCrPt layer is computed from the data, leading to a determination of average CoCrPt stress in the process space. The stress state in the Cr layer is controlled by a reduction in argon sputter pressure to introduce atomic shot peening. An outline for further experimental work is developed View full abstract»

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  • Low-noise automated measurement system for low-frequency current fluctuations in thin-oxide silicon structures

    Page(s): 585 - 589
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    A description is given of the design of an automated system for low-noise measurement of low-frequency current fluctuations in thin-oxide silicon devices. The aim of these measurements is to study the current tunneling through the oxide, and to investigate its correlation with the oxide breakdown. The dedicated system is realized by integrating a personal computer commercial acquisition board with custom high-sensibility low-noise preamplifiers View full abstract»

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  • Measurement of signal parameters by using nonlinear observers

    Page(s): 354 - 357
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    A method to design absolutely stable observers for multiple-output time-varying free nonlinear dynamical systems is presented. This method can be used to measure even those signal parameters that are nonlinear functions of the observations. An adaptive Fourier analyzer has been designed by using the proposed method. Simulation and realization results of this observer are provided View full abstract»

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  • A review of near-field antenna measurements at NIST

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    Summary form only given. The authors present the theory underlying probe-corrected near-field antenna measurements from which the far-field gain, pattern, and polarization may be determined. This theory allows for the rigorous compensation for the effect of a probe which does not measure the field at a point, but rather from an average over the aperture of the probe weighted by the characteristics of the probe. By application of the sampling theorem in the analysis, very efficient algorithms based in large part on the fast Fourier transform (FFT) may be employed in the analysis of the data without introducing approximations in the evaluation of the integrals arising in the analysis View full abstract»

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  • A potentiostat based on a voltage-controlled current source for use with amperometric gas sensors

    Page(s): 456 - 459
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    The results of comparing two potentiostat designs are presented. One is based on conventional use of a current-to-voltage converter (CVC); the second is a new design which employs a voltage-controlled current source (VCCS). The performance of the two designs in the time and frequency domains and the signal-to-noise ratio have been characterized. In the VCCS-type potentiostat, instabilities created by the CVC are eliminated. The working electrode of the gas sensor can now be connected directly to ground, improving the signal-to-noise ratio when long cables are used. The VCCS is controlled by the error voltage developed by a difference amplifier that compares the sensor bias voltage between the difference and working electrodes to a preset reference voltage. The VCCS is used to drive the counter electrode to maintain this bias level. Since the error voltage is proportional to the current in the sensor, the error voltage provides a nonintrusive measurement of current View full abstract»

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  • Coarse and fine search methods to identify and measure noisy sinusoidal signals in a spectrum-monitoring system

    Page(s): 297 - 303
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    Crowded broadcasting bands require the use of high-resolution monitoring equipment to measure common-channel signals individually. A measuring system for this purpose based on the FFT (fast Fourier transform) evaluation of the intermediate-frequency signal in a receiver is described. In the system, broadcasting carriers are identified by a coarse search of the spectrum while their parameters are measured to high accuracy by a fine search. Approximating expressions and simulation results are given to determine the false-alarm rate and peak-find probability of the coarse-search method for different weighting functions. For calculation of the variance of the fine-search estimate, a linearized model is derived and the computed variances are compared against simulations. A sample variance is defined which estimates the expected value of the variance of the frequency estimate in the fine search View full abstract»

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  • Novel detector and difference clock circuits for generator frequency error monitors

    Page(s): 192 - 197
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    All detectors are subject to error in difference detection. Where this detection error is integrated by a clock, it may run up to a few seconds, defeating the whole purpose of the clock. A description is presented of an error-free detector circuit which overcomes this problem. In this design, a detector circuit continuously compares the generator clock and the standard clock. Based on the comparison, it outputs up- or down-count pulses appropriately. The unique feature of the difference detector is its absolute zero error in error detection and low cost of manufacture. A difference clock which responds to the up- or down-count pulses supplied by the error detector and displays the error time is also described. This error time clock displays either positive or negative time, depending on the status of the integral error of the power station frequency View full abstract»

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  • High speed, error corrected, vector S-parameter measurements

    Page(s): 27 - 34
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    Techniques are presented that have been successfully utilized in a high-speed vector network analyzer to reduce multistate device test times without reducing measurement confidence or accuracy compared to conventional network analyzers. The technique utilizes conventional S-parameter measurement practices applied in an integrated instrumentation and computer environment. This integrated test station architecture has been realized in the Scientific-Atlanta Model 2096 and is used as the example View full abstract»

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  • Measuring the temperature dependence of resistivity of high purity copper using a solenoid coil (SRPM method)

    Page(s): 213 - 216
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    The resistivity of high-purity copper was measured by a method that estimates resistivity by using the difference in the impedance of a circular multilayer solenoid coil with a cylindrical copper core and an identical coil without a copper core (SRPM method). It was confirmed that an exact measurement of the resistivity of 10-12 Ω-m can be made. The residual resistivity ratio (RRR) of high-purity copper measured at 100 Hz correlates well with the values measured by the DC four-probe method. The existence of frequency dependence was discovered at very low resistivity for high-purity copper. As the measuring frequency is raised, the skin depth seems to affect the surface resistivity due to the oxide coating and dirt on the surface of the samples View full abstract»

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  • Automated swept-angle bistatic scattering measurements using continuous wave radar

    Page(s): 88 - 96
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    A description is given of the automated swept-angle bistatic scattering measurement system. The measurement technique is described, and it is shown that it can provide accurate bistatic scattering from near backscatter through forward scatter. The author shows how the measurement error can be estimated using background data collected during each measurement session. The calibration technique is described, and the phase of the calibrating sphere's measured scattered field is shown to give information about the sphere's position relative to the center of rotation of the measurement system. A method for correcting this phase error is given. The capability of the measurement system is demonstrated by examining the e-plane scattering from an aluminum cube with 0.75 wavelength side length, for broadside incidence View full abstract»

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  • Improved technique for measuring permittivity of thin dielectrics with a cylindrical resonant cavity

    Page(s): 580 - 584
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    A technique for measuring the relative permittivity of thin, low-loss dielectric materials in a cylindrical resonant cavity has been developed. A thin dielectric sample, of unknown characteristics, is placed upon a thicker dielectric sample whose permittivity is well characterized. Both samples are then placed on the end plate in the cylindrical resonant cavity. In this way, the thin sample is placed in a region of the cavity where interaction with the electromagnetic fields is greater. From knowledge of the cavity's resonant frequency, dimensions of the cavity and both dielectric samples, and from the permittivity of the thicker sample, the authors are able to use iterative techniques to accurately determine the permittivity of the thin dielectric sample. A derivation and discussion of the theory used in this layered-dielectric permittivity measurement technique are provided. Measurement results at frequencies between 9 and 10 GHz confirm the accuracy of the technique. Preliminary error estimates are also given to show the worst-case uncertainties associated with this new method View full abstract»

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  • Fiber-optic strain gauge manometer up to 100 MPa

    Page(s): 414 - 417
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    A description is given of the realization of a pressure transducer, utilizing a fiber-optic strain sensor and an active element configured to simulate an infinite cylinder with free ends. The deformation of such a cylinder depends uniquely on the pressure acting from its inside and is independent of the stress resulting from the attachment of the device to the pressure system. The fiber-optic strain sensor is permanently bonded to the external surface of the cylinder and as such is fully isolated from the high pressure region. The sensing element of the device consists of a highly birefringent (HB) polarization-maintaining optical fiber strain gauge. The device was characterized for pressures up to 100 MPa. The sensor has inherent advantages such as immunity to electromagnetic interference, safety in electrically dangerous, hazardous or explosive environments, direct compatibility with optical data transmission systems, simplicity, and cost-effectiveness. It does not require any fiber-optic lead-through since it is located outside the pressure region and has significantly increased sensitivity (around 0.1 MPa-1) over similar devices based on electrical strain gauges View full abstract»

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  • A semi-fixed frequency method for evaluating the effective resolution of A/D converters

    Page(s): 51 - 54
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    A detailed description of an algorithm for the effective bit test in noncoherent conditions is presented. This algorithm offers reasonable convergence and accuracy advantages over existing methods. A flow diagram for the algorithm and its implementation using the MATLAB package is included. The metrological reliability of input data is checked. An adopted ZEROIN program and Householder orthogonalization are applied to estimate the starting point of an iterative process, and the Newton's method is involved in a final calculation for the best-fit curve to the input data View full abstract»

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  • Instrumentation and measurement for a submillimeter-wave planar diode mixer

    Page(s): 147 - 149
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    The design of a planar diode submillimeter-wave mixer is presented in which scale models play an important role. By constructing larger scale models of mixer components the design process is simplified by making component changes easier and by making the measurements easier with the aid of a network analyzer. Separate scale models were used to find: optimum diode geometry; a microstrip low-pass filter; and a wide-bandwidth transition from circular waveguide to shielded microstrip. After combining the results from these measurements to form a mixer circuit model, the combined effect of the various components was studied and adjustments were made to present an optimum impedance to the diode terminals. Tests of the design at 345 GHz confirm the accuracy of the design procedure View full abstract»

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  • Measurement and use of dielectric properties of agricultural products

    Page(s): 636 - 640
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    The dependence of the dielectric properties of materials on other variables is discussed as it relates to agricultural products. Measurement techniques for determining dielectric properties of such materials are reviewed briefly, and graphical data are presented to illustrate the dependence of dielectric properties of some products on frequency and moisture content. Several agricultural applications are discussed in which dielectric properties information is useful View full abstract»

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  • New capacitive linear and rotary displacement transducers having extremely high both linearity and sensitivity

    Page(s): 406 - 409
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    The basic principle adopted in the design of new transducers is illustrated. This principle is based on the adoption of a very thin dielectric film between the electrodes. The film may be obtained either in micrometrical thickness, 1-3 μm, by a dielectric spray varnish or, as illustrated in the features of an improved design, in submicrometrical, <1 μm, thickness by metallic dielectric deposition in gas phase. The transducers are designed in a differential form. Their electrodes have to be constructed by photochemical etching. Prototypes of the illustrated transducers have been constructed and the test results obtained on them are analyzed. On the basis of the test results obtained, the proposal for a variable absolute capacitor and capacitive voltage divider is presented View full abstract»

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