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Instrumentation and Measurement, IEEE Transactions on

Issue 5 • Date Oct 1990

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Displaying Results 1 - 25 of 26
  • High speed data collection system for magnetic field imaging by CT technique

    Page(s): 739 - 744
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (508 KB)  

    A method of high-speed data collection used in imaging the magnetic-field distribution leaking from magnetic devices along any plane is proposed. The method uses the computed tomography (CT) technique. A high-speed data collection system developed for demonstrating the method is described. An image of the magnetic field is reconstructed from projection data provided by the voltage induced in the sensors of a line conductor and a rectangular coil moving in the plane of observation. Rotational scanning of the sensors is used for collecting the projections so that data-acquisition time can be reduced. To demonstrate the performance of the system, the reconstructed images of the magnetic-field distributions made by some permanent magnets are shown View full abstract»

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  • A high-quality dual-input differentiator

    Page(s): 726 - 729
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (220 KB)  

    A dual-input ideal differentiator network design with a single resistor-controlled time constant and high-gain operational amplifier (OA) devices is described. At high frequencies, the network becomes functionally nonideal and its quality factor (Q) degrades because of the frequency-dependent gain of the OA. A suitable Q-compensation design that yields a 1:|A|2 order of Q improvement at higher frequencies is proposed. The network exhibits high-frequency deemphasis characteristics due to the OA-poles which would suppress the high-frequency noise components View full abstract»

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  • A high accuracy, low power, reproducible temperature telemetry system

    Page(s): 773 - 779
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (516 KB)  

    A low-power temperature telemetry system incorporating a miniature micropower temperature sensor/modulator and hand-held decoder with direct digital readout is described. The system is designed to avoid the need to calibrate and characterize individual units while guaranteeing an accuracy of ±0.25°C and a resolution of 0.1°C. The combined sensor and transmitter is constructed using thick-film technology and weighs less than 2.5 g without batteries. Developed principally for wild life tracking and monitoring, the system also has other applications where remote environmental monitoring is required View full abstract»

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  • A microwave method to measure unburnt coal content in ashes

    Page(s): 804 - 806
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    A procedure for determining of the unburnt coal content in ashes of combustors without a detailed chemical analysis is proposed. The method is based on measurements of the modulus of the reflection coefficient of a sample holder loaded with the test sample View full abstract»

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  • Error-detecting unit-distance code

    Page(s): 730 - 734
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    A particular kind of unit-distance code is proposed. Unit-distance codes are applied especially to absolute encoders (linear or rotary). The various positions of the encoder are represented by the various code words of the code. In contrast to conventional unit-distance codes, this code offers the possibility of detecting all single-bit errors except the two single-bit errors that cause a code word which represents the adjacent position. Unit-distance codes are characterized by a Hamming distance of 1. Thus, Hamming distance is not a unit of measurement for the code's error-detection ability. Therefore, a Hamming distance is defined especially for unit-distance codes excluding the adjacent code words from the calculation of distances. An application shows the utility of the code in the field of instrumentation and measurement View full abstract»

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  • Measurement of contact resistance with microampere currents

    Page(s): 711 - 714
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (248 KB)  

    The design of an instrument for measuring contact resistance is presented. The design incorporates photo-isolated synchronous rectification. The noise in this instrument is suppressed to 0.1 nV, and contact resistance can be measured with low currents of 0.1 to 100 μA. Several types of contacts are measured with this low-current instrument. When the contacts are contaminated, they are likely to indicate higher resistance than that measured at milliampere currents with widely used commercial instruments. The instrument is clearly effective and the measurement with microampere currents is important for estimating contact resistance under conditions close to actual use View full abstract»

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  • Noise thermometers for hostile environments: a theoretical evaluation

    Page(s): 780 - 784
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    The theory of the operation of noise thermometers in hostile environments is described. The unknown parameters of the measurement system are identified and analytical and experimental efforts required for application of noise thermometers for temperature measurements in hostile environments such as nuclear reactors are delineated View full abstract»

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  • The ratio error of the overlapped-tube cryogenic current comparator

    Page(s): 689 - 697
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (660 KB)  

    Analytic expressions for the ratio uncertainty of the overlapped-tube cryogenic current comparator are derived for dimensioning the overlapped-tube comparator. Theoretical predictions agree reasonably well with experimental observations by H. Ramin (Arch. Elektrotech., vol.58, p.53, 1976). The construction of a very sensitive cryogenic current comparator and the possibility of minimizing the ratio uncertainty by reducing the size of the detection coil are also discussed View full abstract»

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  • A time-domain approach to reactive current minimization in nonsinusoidal situations

    Page(s): 698 - 703
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (392 KB)  

    For the optional LC compensator design, the RMS (root mean square) values of the sources voltage harmonics and the load susceptances, have to be measured. It is shown that the optimal capacitance of such an LC compensator can be determined in the time domain without this information. This can be done by an iterative procedure which requires that the scalar product of the load current and the derivative of the capacitor voltage and their RMS values be measured View full abstract»

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  • An accurate wide-band phase shifter for sinusoidal signals using a narrow pulse duty cycle network

    Page(s): 801 - 804
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (236 KB)  

    A technique for producing a constant phase shift of sinusoidal signals independent of frequency by using a narrow pulse switching network is proposed. A phase-locked loop circuit multiplies the frequency of the input signal by an integer factor N and, with a monostable vibrator, provides narrow pulses which excite the MOSFET switches of the network. The working frequency range of the circuit extends to more than five decades and gives a maximum error that cannot exceed 360/N° View full abstract»

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  • Development of a polarimetric optical fiber sensor for electronic measurement of high pressure

    Page(s): 715 - 721
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    The theoretical understanding of the principle of pressure-induced polarization coupling is discussed, and the improved construction, operation, and temperature desensitization of a high-pressure (up to 100 MPa) fiber-optic sensor in two configurations is described. The sensor exploits the effect of polarization coupling between two orthogonally polarized eigenmodes of a highly birefringent, polarization-preserving optical fiber which serves as the sensing element. An idea of temperature desensitization of the sensor output signal is demonstrated. The requirements for an electronic measurement system based on the sensor are discussed, including indentification of the parametric and functional specifications and constraints of such a system View full abstract»

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  • The importance of measurement in technology-based competition

    Page(s): 685 - 688
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (348 KB)  

    Challenges in measurement are related to the changes taking place in emerging technologies, quality assessment, and production. Strategies in product genesis and quality are discussed together with the impact of emerging technologies. The differences between traditional and modern approaches in measurement and instrumentation are compared View full abstract»

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  • A new minimum component active-C OTA-based linear voltage (current)-controlled sinusoidal oscillator

    Page(s): 795 - 797
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (264 KB)  

    A transconductance-amplifier-capacitor sinusoidal oscillator is introduced. The circuit requires only two operational transconductance amplifiers (OTAs) and two grounded capacitors. The frequency of oscillation is linearly tunable over a wide frequency range View full abstract»

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  • Demagnetization effect of rectangular and ring-shaped samples made of electrical sheets placed in a stationary magnetic field

    Page(s): 704 - 710
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (504 KB)  

    The method of summation used for calculating magnetic-field strength is applied to determine the demagnetization coefficient of rectangular and ring-shaped samples made of an anisotropic electrical sheet and of isotropic silicon and silicon-free sheets. The calculations refer to a standard strip used in an Epstein test (of its shortening and contraction) and to the sample which is usually placed in an anisometer, i.e. in a homogeneous external magnetic field. Changes in the demagnetization coefficient are determined for different crystallographic orientation in the above-mentioned sheets. The relation between the magnetization direction of the ring-shaped sample and its demagnetization is affected. In the case of electrical steel strips, the results allow the determination of the real magnetization characteristics for the sample View full abstract»

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  • Measurement and analysis of the indoor radio channel in the frequency domain

    Page(s): 751 - 755
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (348 KB)  

    Using a network analyzer, several experiments for the frequency-domain characterization of the indoor radio channel in the 0.9-1.1-GHz band are performed. In the experiments, the frequency response measurements are taken at spatially distributed locations throughout the test area by fixing the receiver in a central location and moving the transmitter to different locations. The experiments are performed in a high-rise office building and a three-story building with offices and laboratories. For each experiment, the exponent of the power-distance relationship and the statistics of the 3-dB width of the frequency correlation function are determined from the frequency-domain data. The approximation to the impulse response of the channel is obtained from the inverse Fourier transform of the frequency response. An empirical exponential relationship between the 3-dB width of the frequency correlation function and the inverse of the RMS (root mean square) delay spread of the impulse response is derived View full abstract»

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  • A new current measurement method in resistance spot welding

    Page(s): 767 - 772
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (360 KB)  

    A method of measuring the high current in resistance welding processes is investigated. A measuring unit is developed by using a strain gage attached on the outer surface of a steel ring. The steel ring is placed around a section of the secondary loop of the welding machine and is deformed by electromagnetic forces induced by the high welding current. The circumferential constituent of the ring deformation is then used to obtain a signal voltage proportional to the secondary welding current. The strain gage signal of ring deformation is enough to determine the welding current in resistance spot welding, especially when direct current is used for the welding View full abstract»

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  • An electronic integrating heat meter

    Page(s): 785 - 789
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    The heat energy consumed by individual customers in a district heating system that uses hot water is found by integrating the flow rate (volume/second) and multiplying it by the temperature difference between the incoming and outgoing water. An electronic integrating heat meter is developed for this purpose using a programmable unijunction transistor (PUT) and linearized thermistor sensors. The temperatures of the incoming and outgoing radiator water are measured by means of the thermistor sensors mounted on the pipes connected to the radiator, and their temperature difference is converted to a current. The current is applied to a current-to-pulse frequency converter using the PUT that operates only during the time of the constant width of the pulses generated by a water-flow meter and correspond to the water-flow volume. Therefore, the number of counted output pulses of the current-to-pulse frequency converter shows the integrated multiplication of the flow rate and the temperature difference, which is the heat energy. The electronic circuit is simple and therefore not expensive. The accuracy of the heat meter is within ±2% for a temperature difference up to 40°C View full abstract»

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  • Implementation of digital signal processing techniques in the design of thermal pulse flowmeters

    Page(s): 761 - 766
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    Various digital signal processing methods, which could be applicable to the design of a microcomputer-based thermal pulse flowmeter, are examined. Two excitation methods are investigated: a single thermal pulse, and a pseudorandom binary sequence signal (PRBS). The signal recovered downstream is processed by two alternative numerical algorithms to recover the time of flight (i.e. by peak detection of the signal itself and the peak of the differentiated signal). The recovered thermal pulse and the time of flight are then used to test the validity of two models: a diffusion-advection model and a simple time-delay model. The delay model is found to be compatible with the data, especially when the peak of the output signal derivative is used as a marker for determining the time of flight. The single-pulse injection method is found, in general, to be superior to the PRBS cross-correlation technique, except for the ability of the latter to provide early indication of flow-rate variations View full abstract»

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  • Stokes-parameter photopolarimeter using an optically or mechanically rotatable two-detector assembly

    Page(s): 722 - 725
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (280 KB)  

    A two-detector photopolarimeter for measuring the four Stokes parameters of a monochromatic or quasi-monochromatic light beam in an arbitrary state of partial elliptical polarization is described. Each detector is partially specularly reflecting at oblique incidence, and the plane of incidence is rotated (by other than 90°) between the two successive reflections. The two-detector assembly is itself rotated manually or with a stepping motor solidly as one unit around the axis of the incident beam. Mechanical rotation may be eliminated by using a Faraday rotator in front of a stationary arrangement of two detectors. Conditions under which singularities may occur (which lead to an incomplete measurement of polarization) are discussed. Optimum geometry and detector-surface characteristics are identified View full abstract»

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  • A switched-capacitor interface for capacitive sensors based on relaxation oscillators

    Page(s): 797 - 799
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (252 KB)  

    A switched-capacitor (SC) interface for capacitive sensors based on a modified Martin's relaxation oscillator is proposed. The output signal is the duty-cycle of a pulse-width modulated square-wave voltage or a binary-coded digital signal which is directly related to the capacitance ratio of an unknown capacitance and reference capacitance. The circuit can be implemented in a monolithic IC form using CMOS technology. It requires a relatively small device count integrable onto a small chip area and its suited particularly for the on-chip interface circuitry for microprocessors View full abstract»

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  • Turn-tester for windings with a magnetic core

    Page(s): 799 - 801
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (252 KB)  

    A turn-tester for windings on a magnetic core is described. A temporary winding is wound on the core to form a current transformer. Based on the principle of current comparators for calibrating current transformers, the error of the current transformer thus formed is measured. The number of turns can be correctly determined from the characteristics of this current transformer. With an error of 2×10 -5 , the accuracy of this type of turn testing is very high, especially for cores made of iron-nickel alloy. An error on the order of 0.1% to 0.01% is attainable, which means that an error of less than 1 turn is possible when the number of turns is less than 1000 to 10000 View full abstract»

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  • Development of a microprocessor-based four probe DC resistivity setup for Tc measurement of superconducting materials

    Page(s): 792 - 795
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (316 KB)  

    The design of a microprocessor-based resistivity measurement system for high transition temperature (Tc) superconducting materials is described. This design includes interfacing an Intel 8085 microprocessor system with an IBM-compatible personal computer (PC) through RS-232C serial communication. This design is used to measure resistivity for superconducting samples of YBa2Cu 3O7-x and strontium/potassium substituted YBa2Cu3O7-x. A correction method is described for the parameters whose values are changing throughout the measurement period to minimize the measurement errors View full abstract»

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  • X- and γ-rays computerized minitomograph scanner for soil science

    Page(s): 745 - 750
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (424 KB)  

    A computerized tomograph scanner system that uses X- and γ-rays for applications in soil science is described. Use of the apparatus in measuring volumetric water content to an accuracy of ±3% and soil bulk density to ±2% (in grams per cubic centimeters) is discussed. The system features translation and rotation scanning modes, a 200-mm effective field of view, signal processing by pulse counting, and 1.0-mm spatial resolution. The system's advantages over classical methods are listed, principles of the tomographic method and physical considerations are presented, and the system's design is described View full abstract»

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  • Computer control of a slow-AC technique for thermopower measurements

    Page(s): 756 - 760
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (480 KB)  

    A measurement algorithm and the required instrumentation for computer automation of temperature-dependent thermopower measurements over the range of 4.2 to 350 K are described. The performance of the measurement system is demonstrated by examining typical results obtained on bulk and thin film samples of the thallium-based ceramic superconductor. The quality of the measurement data obtained is improved by increasing the density of the collected data and by improving reproducibility of the results View full abstract»

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  • Noise analysis for the triaxial capacitive displacement transducer

    Page(s): 735 - 738
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    A computer simulation and experimental study of electric noise in the triaxial capacitance displacement transducer is presented. When combined with a measurement instrument, the simulation and study lead to an optimal design range for the value of the reference capacitor of the transducer. The range is defined in terms of the decrease in noise, relative to the increase in capacitance. A SPICE program is used to predict the noise characteristics of the triaxial displacement transducer. It is found that the signal-to-noise ratio improves as the reference capacitance of the device is increased, but also that the rate of improvement decreases with an increase in capacitance 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.

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Editor-in-Chief
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