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Instrumentation and Measurement, IEEE Transactions on

Issue 2 • Date June 1987

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Displaying Results 1 - 25 of 116
  • Table of contents

    Page(s): 1
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  • [Inside front cover]

    Page(s): c2
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  • Foreword

    Page(s): 149 - 152
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  • Editorial

    Page(s): 153 - 154
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  • Quantum mechanics and precision measurements

    Page(s): 155 - 157
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    The quantum mechanical foundation of modern precision physical measurements is discussed with emphasis on five key features of quantum mechanics which underlie such measurements. It is argued that quantum theory affords more advantages than limitations for achieving high precision in determination of fundamental constants and related quantities. View full abstract»

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  • News from the BIPM concerning the meter, the kilogram, the second, and the ampere

    Page(s): 158 - 160
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    Some new aspects of the tasks of the Bureau International des Poids et Mesures (BIPM) are outlined. They arise from the extended use of stabilized lasers as practical standards for length measurement; the need for a better insight into the long-term maintenance of mass standards exposed to pollution, implying improvement of balances and air-buoyancy correction; the transfer to BIPM of the responsibility for the International Atomic Time Scale (TAI), including coordination of clock comparisons, collection, analysis, and treatment of data, and distribution of TAI; and the use of quantized references for the maintenance of stable and reproducible representations of the volt and the ohm based upon the Josephson effect and the quantum Hall effect. Although news in the fields of time and electricity is more relevant to the traditional interests of the Conference on Precision Electromagnetic Measurements (CPEM), the expansion of the CPEM's depth of interest in the area of fundamental constants makes it appropriate to include some remarks on length and mass. View full abstract»

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  • The Avogadro constant — Recent results on the molar volume of silicon

    Page(s): 161 - 165
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    The density p of two silicon crystals has been determined by precision hydrostatic weighing, based on very accurate solid density standards (SDS's). Densities of additional crystals were gained from density differences measured by the temperature-of-floatation method. The molar mass M of the crystals was determined by comparing the isotopie abundances against the known abundances of the National Bureau of Standards (NBS) reference material SRM 990 using activation analysis and mass spectroscopy. Combining the measured values for M and p leads to M/p = (12.058 822 ± 0.000 013) cm3/mol. With the known volume of the unit cell the following value for the Avogadro constant was calculated: NA = (6.022 137 ± 0.000 007) × 1023 mol−1. View full abstract»

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  • Remeasurement of a Silicon lattice period

    Page(s): 166 - 169
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    Opitcal interferometry of an Silicon lattice period is an important link between macroscopic and microscopic lengths as well as between low-energy and high-energy spectroscopies. An evident discrepancy between two pre-1982 measurements has limited the effective application of these results. Very recent results, reported here in a preliminary way, appear to further understanding and removing this discrepancy. View full abstract»

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  • Superconducting thin-film gyroscope readout for Gravity Probe-B

    Page(s): 170 - 174
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    We describe the high-resolution gyroscope (gyro) readout system for the Stanford Gravity Probe-B experiment, whose purpose is to measure two general relativistic precessions of gyroscopes in Earth orbit. In order to achieve the required resolution in angle (0.001 arc · s), the readout system combines high-precision mechanical fabrication and measurement techniques with superconducting thin-film technology, ultra-low magnetic fields, and Superconducting Quantum Interference Device (SQUID) detectors. We discuss system design, performance limits achievable with current technology, and the results of fabrication and laboratory testing to date. View full abstract»

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  • Precision NMR measurement of 7Li and limits on spatial anisotropy

    Page(s): 175 - 180
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    7Li NMR is observed with 7LiCl in D2O using a Nicolet NT-360 NMR Spectrometer over a 3.5 month period. The linewidth is typically about 40 mHz. Fitting to a triple Lorentzian line shape gives the splitting Δf ≲ 2.2 mHz which is roughly 20 times better than previous experiments. This result puts a limit on mass anisotropy Δm /m and the nonuniversality |Hij − gij| of the gravitational coupling Hij to electromagnetism and the gravitational coupling gij, to particle mass as follows: δm/m < 2 × 10−24, Hμν − gμν | / U ≤ 10−13, | H − g | / U ≤ 10−8 ∼ 10−9, and | H00 − H00 | / U ≤ 10−5. View full abstract»

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  • Quantum measurements of position, detection of weak classical forces, and interferometric noise

    Page(s): 181 - 184
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    We discuss quantum measurements of position and repeated-measurement schemes for monitoring free-mass position to an arbitrary accuracy. Using these schemes, weak classical forces can be monitored to an arbitrary accuracy. To illustrate various measurement uncertainties and intrinsic uncertainties, we consider the case of a Michelson interferometer. In the low-intensity limit, two measurement uncertainties, photon counting error and radiation pressure error, are independent of the intrinsic uncertainty. The uses of squeezed states and number eigenstates are discussed. View full abstract»

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  • Volt balance realization of the volt at ETF in Zagreb

    Page(s): 185 - 189
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    A volt balance having plate electrodes operating in a temperature-controlled atmosphere of dry nitrogen is described. The voltage is measured by a special procedure of substitution of a weight for the electrostatic force, with automatic control of the balance equilibrium. This, together with the application of very sensitive capacitive transducers for measuring the balance equilibrium and electrode displacements enables a weighing reproducibility of less than 0.1 ppm to be achieved. The earthed electrodes are suspended over the beam arms by means of two thin strips separated one from the other in such a way that optimal sensitivity to the existence of horizontal electrostatic forces is achieved. Through the remote adjustment of the horizontal position of the high-voltage (H-V) electrodes, and by measuring the displacement of the suspended and H-V electrodes, it is possible to eliminate horizontal electrostatic forces. The displacement of the H-V electrodes by 51 mm (corresponding to a capacitance change of 100 pF) enables highly precise capacitance and length measurements to be made. The third improved version of the Zagreb Faculty of Electrical Engineering (ETF) volt balances is now being completed. The mean result of six measurements obtained with two earlier balances indicates that the difference between the International System (SI) volt determined by the ETF volt balances and volt BI-76 is +7.1 ppm with a random one-standard-deviation (1σ) uncertainty of 0.4 ppm and a systematic 1σ uncertainty of 1.6 ppm. View full abstract»

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  • Twenty years of SI ohm determinations at NML

    Page(s): 190 - 195
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    The National Measurement Laboratory (NML) of Australia has maintained an absolute standard of resistance based on a calculable capacitor for more than 20 years. Since its inception, various developments have been incorporated which contribute to a reduction in the overall uncertainty. A reassessment of uncertainties gives a figure now of 6.2 in 108 for the ohm. A systematic error, introduced in 1974, has been identified, and a corrrection of −0.09 ppm should be made to resistances expressed in terms of the NML ohm since that time. View full abstract»

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  • The low-field proton gyromagnetic ratio γ′p experiment at the ETL

    Page(s): 196 - 200
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    The low-field proton gyromagnetic ratio γ′p(low) experiment at the Electrotechnical Laboratory (ETL) has been continuing with the construction of a new nonmagnetic building, precision solenoid, and dimensional measuring apparatus. A tentative value of γ′p(low)ETL86 and its uncertainty are given: γ′p(low)ETL86 = 2.6 751 289(59) × 108 s−1T−1ETL (2.2 ppm). The sources of uncertainty have been carefully investigated. The irregularity of the solenoid diameter and the resistance calibration mainly caused the large uncertainty. In order to reduce the uncertainties some improvements have been done or are planned. View full abstract»

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  • The anomalous magnetic moment of the electron and the quantum electrodynamics determination of the fine-structure constant

    Page(s): 201 - 204
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    We report the present status of our calculation of the eighth-order quantum electrodynamics (QED) contribution to the electron anomalous magnetic moment ae. Combining the tentative result with the very precise measurement of ae by the University of Washington group, one can determine the fine-structure constant a to a precision of 2 × 10−8. Our result is compared with other determinations of a including that of the quantized Hall effect. View full abstract»

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  • Absolute determination of the farad and the ohm, and measurement of the quantized Hall resistance RH(2) at LCIE

    Page(s): 205 - 207
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    A calculable five-electrode cylindrical capacitor is used at Laboratoire Central des Industries Electriques (LCIE) for the absolute determination of the farad. The ac measurements linking the calculable standard to the resistors of a quadrature bridge are made at two different frequencies: ω = 2500 rad /s and ω = 5000 rad/s. The resistors of the quadrature bridge are linked to ΩLCIE and to the quantized Hall resistance RH(2) thanks to a resistance ratio measurement bridge using a cryogenic dc current comparator. The total one-standard-deviation (1σ) uncertainty on the measurement of RH(2) is 2.2 × 10−7. View full abstract»

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  • The relationship between the SI Ohm, the Ohm at NPL, and the quantized Hall resistance

    Page(s): 208 - 213
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    New measurements relating the quantized Hall resistance RH(= h/ie2), International System (SI) Ohm (ΩSI), and the National Physical Laboratory maintained ohm (ΩNPL) have now been completed at NPL in the U.K. with improvements and simplifications in the cryogenic current comparator measurements and 1000-Ω dc resistance measurements. From the measurements over the past four years the relationship between ΩNPL and ΩSI can be described by the equation ΩNPL − ΩSI = −1.049(0.020) − 0.0478(0.0074)[t − 1986.0] μΩ in which t is measured in years. For the previous two years the equivalent relationship between RH and ΩNPL is RH = 25 812.8(1 + 1.452(0.038) × 10 −6 + 0.0694(0.0772) · [t − 1986.0] × 10−6) ΩNPL in which the uncertainties (in parentheses) are one-standard-deviation (1σ) random uncertainties of the least squares fit to the data. Combining the most recent measurements of RH and ΩSI, using a more direct method of measurement RH = 25 812.8106(17) ΩSI in which the relative combined uncertainty is 0.067 × 10−6. View full abstract»

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  • Determination of the quantized hall resistance value by using a calculable capacitor at ETL

    Page(s): 214 - 217
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    We report the International System (SI) value of the quantized Hall resistance (RH) determined by using a calculable capacitor at the electrotechnical laboratory (ETL). As the result of our measurements at ETL, a most reliable value of h / e2 has been estimated as 25 812.8036 ΩSI with a systematic uncertainty of 0.25 ppm root sum square (rss) and a random error of 0.20 ppm one standard deviation (1σ). View full abstract»

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  • Quantum Hall measurements from 4 K to 20 mK

    Page(s): 218 - 221
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    We report on precision measurements of the quantum Hall resistance (QHR) in the temperature range of 20 mK to 4 K. These include intercomparisons of the ohm maintained at the National Research Council (OHM NRC) and the International System ohm (OHM SI) and the QHR. The effects of nonzero Rxx minima, sample inhomogeneity, nonohmic contacts, and dissipation are summarized. View full abstract»

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  • Monitoring the U.S. legal unit of resistance via the quantum Hall effect

    Page(s): 222 - 225
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    The quantum Hall effect is being used to monitor the resistances of the five 1-Ω Thomas-type resistors which define the U.S. legal unit of resistance, the ohm maintained at the National Bureau of Standards (ΩNBS). Typically, the total one-standard-deviation (1σ) accuracy for the transfer between three different GaAs quantum Hall devices and the five 1-Ω resistors is ±0.05 ppm. Measurements to date provide the first direct evidence that the value of ΩNBS is decreasing by about (0.05 ± 0.02) ppm per year. View full abstract»

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  • Precise comparisons of quantized Hall resistances

    Page(s): 226 - 229
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    A method allowing the comparison of quantized Hall resistances RH with an uncertainty of ∼4 × 10−9 is described. Results are presented for six heterostructures (five GaAs-AlxGa1−x As type and one InGaAs-InP type). The differences between the quantized Hall resistances RH(2) or RH(4) for four different GaAs-based samples are lower than ±5 × 10−9. View full abstract»

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  • An improved Josephson potentiometer system for the measurement of the quantum Hall effect

    Page(s): 230 - 233
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    Several improvements have been made on a Josephson potentiometer and superconducting quantum interference device (SQUID) galvanometer system previously reported. Results of the measurement of the quantized Hall resistance obtained by the use of this system are in agreement with those obtained by means of a conventional potentiometer system to 0.02 ± 0.08 ppm for silicon-MOSFET samples. A comparison of the Hall resistance between two different quantized values corresponding to h/4e2 and h/8e2, for a sample, has been made without an uncertainty associated with the linearity of voltage-ratio measurements. A discussion is presented in relation to completeness of the quantization. View full abstract»

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  • The realization of the quantum Hall standard of resistance at the BIPM

    Page(s): 234 - 239
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    The first measurements of the quantum Hall resistance at the Bureau International des Poids et Mesures (BIPM) have been carried out using a silicon MOSFET sample at magnetic flux densities up to 13.2 T and at temperatures near 0.5 K. New measurement equipment has been constructed and used to establish an accurate link to the present resistance standard with a relative uncertainty, given as a one-standard-deviation estimate, of 7.6 × 10−8. The results are 4RH (4) = (25 812.8511 ± 0.0020) Ω69-BI for June 1, 1986. Using the very recently revised value for the relation between Ω69-BI and the Commonwealth Scientific and Industrial Research Organization (CSIRO) determinations of the ohm gives 4RH (4) = (25 812.8087 ± 0.0027) Ω. View full abstract»

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  • The quantum Hall effect as a standard to define the laboratory unit of resistance

    Page(s): 240 - 244
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    A measurement system has been developed to determine the resistance of integer quantum Hall plateaux relative to a room-temperature reference resistor network of nominally the same values. Silicon MOSFET and GaAs-AlGaAs samples have been successfully fabricated and measured. The results confirm that the integer quantum Hall effect (QHE) may be used to monitor a group of standard resistors comprising the laboratory unit of resistance. They demonstrate the feasibility of defining the laboratory unit of resistance by adopting a value for the quantum Hall resistance h/e2. View full abstract»

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  • Quantized Hall resistance measurement at the NML

    Page(s): 245 - 248
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    An automatic measurement system has been used to determine the values of quantized Hall resistances RH in terms of the National Measurement Laboratory (NML) realization of the International System (SI) ohm. The quantized Hall resistances of two GaAs-AlGaAs heterostructures were measured. The n = 2 step of one heterostructure and the n = 4 step of the other were measured over a seven-month period. A weighted mean of these determinations gave a value for the quantity RH(n = 1) of 0.383 ppm (0.078 ppm one-standard-deviation (1σ) uncertainty) above the nominal 25 812.80 Ω in SI units. 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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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