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Instrumentation and Measurement, IEEE Transactions on

Issue 4 • Date Nov. 1972

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Displaying Results 1 - 25 of 61
  • Table of contents

    Page(s): c1 - 8b
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  • IEEE Instrumentation and Measurement Group

    Page(s): c2
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  • [Advertisement]

    Page(s): nil1 - 306
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  • IEEE G-IM-An Invitation

    Page(s): 305
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  • Foreword

    Page(s): 307 - 308
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  • CPEM '72 in Retrospect Editorially

    Page(s): 309
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  • Recent NPL Work on the AC Josephson Effect as a Voltage Standard

    Page(s): 310 - 314
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    The experimental equipment and procedure used in the latest National Physical Laboratory (NPL) ac Josephson effect determinations of 2e/h are described. The most recent value, obtained in April 1972, is 483 594.00 (±0.10) GHZ/VNPL and this, together with earlier results, provides information concerning the stability of the NPL maintained voltage standard over the past two years. To obtain a further increase in precision, new equipment is being developed for the measurements in which the resistive divider and null detector are maintained at cryogenic temperatures. View full abstract»

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  • Recent Progress of the 2e/h Measurement at PTB

    Page(s): 314 - 315
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    In this paper, an experimental setup is described with which the stability of the PTB voltage standard, consisting of a group of International Weston cells, can be monitored with a total uncertainty (1¿) of 4 parts in 108 by means of the ac Josephson effect. The measured quotient of the fundamental constants 2e/h is given by 2e/h = (483 593.606 ± 0.020) GHZ/VPTB, May 1972. View full abstract»

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  • Summary of International Comparisons of As-Maintained Units of Voltage and Values of 2e/h

    Page(s): 316 - 319
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    Using temperature-regulated transportable standard-cell enclosures, the National Bureau of Standards (NBS), under the auspices of the Bureau International des Poids et Mesures (BIPM), during the period June 1971 through June 1972 has carried out a series of direct comparisons of the units of voltage as-maintained by NBS and BIPM, Sÿvres, France; the National Physical Laboratory, United Kingdom; the National Research Council, Canada; the National Standards Laboratory, Australia; and the Physikalisch-Technische Bundesanstalt, Germany. The main purpose of these comparisons was to provide a sound basis for intercomparing values of 2e/h obtained at the various national laboratories via the ac Josephson effect in superconductors. It was found that when converted to a common unit of voltage, most measured values of 2e/h agreed with each other to within the 1 to 2 parts in 107 estimated uncertainty (1 standard deviation) of the volt comparisons. This satisfying result would seem to indicate that serious consideration should be given to adopting a single international value of 2e/h for use in maintaining units of voltage. View full abstract»

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  • Standard cells with Cd-Pb amalgam electrode

    Page(s): 319 - 323
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    In order to improve the characteristics of standard cells, those containing composite amalgam electrode have been studied. The criterion and test procedures established for selecting high-quality standard cells have been applied. The addition of Pb to Cd amalgam has the effect of reducing the temperature coefficient. The most appropriate composition of amalgam is that of 10 wt % Cd, 3-9 wt % Pb, and the balance Hg. The cells with Cd-Pb amalgam electrode have an EMF higher by about 1000 ¿V than that of normal Weston cell, and a temperature coefficient at 20° C or -17 μV/°C. The other characteristics and stability are the same as those of normal cells and they are suitable for high-precision work. Although zero temperature coefficient may be obtained by adding Pb and Bi to Cd amalgam, its characteristics are inferior to those of normal cells. View full abstract»

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  • A High-Accuracy Digital Instrument Design for DC Measurements

    Page(s): 323 - 328
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    A high-accuracy self-calibrating digital instrument design has been developed in order to make available the inherent efficiency advantages of conventional digital meters, but without their limitations in accuracy, reliability, or certifiability. The new instrument can extend the advantages of automation to many testing, quality control, and standards laboratories where heretofore only high-quality manually balanced instruments could be used. Automation at this level of accuracy can eliminate serious cost bottlenecks in the testing of precision devices such as Zeners, resistors, A/D and D/A networks and converters, standard cells, regulated power supplies, voltage and current sources, digital and differential voltmeters and potentiometers, and the dc output of many precision transducers. The paper describes a number of applications of this new type of digital instrument and presents samples of the type of automatic test data obtained. View full abstract»

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  • High-Precision Digital Volt Ratiometer by a Method of Measuring Difference of Magnetic Field among Three Windings

    Page(s): 329 - 333
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    The purpose of this work is to establish a highly accurate automatic ratio measuring instrument for dc voltage and resistance. In voltage and resistance ratio measurements, accuracy of 0.1 ppm has now become necessary due to recent developments in quantum metrology. To obtain the accuracy, we have just developed a technique to automatically compensate the measuring error caused by the deviation of electrical components, such as resistances used in the instrument. The instrument described incorporates this technique. With internal reference voltage and resistance, it can be a precision voltohmmeter and also, it can be standardized to an external standard with an accuracy of 0.1 ppm. View full abstract»

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  • Theoretical Analysis of the AC/DC Transfer Difference of the NPL Multijunction Thermal Convertor over the Frequency Range DC to 100 kHz

    Page(s): 334 - 340
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    Measurements of the rms values of alternating currents are frequently made by means of thermal transfer instruments. At low and midfrequencies Thomson heating can have an important influence on the ac/dc transfer difference of these devices, whereas at higher frequencies the variation with frequency of the effective resistance of their heaters is the most decisive factor. The present paper examines the influence of both Thomson heating and the reactive components of the heater on the performance of the NPL multijunction convertor, and sets out the theoretical analysis that supports the claim that its ac/dc transfer difference does not exceed 1 or 2 ppm up to a frequency of 100 kHz. View full abstract»

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  • Wide-Band Two-Stage Current Transformers of High Accuracy

    Page(s): 340 - 345
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    The design and performance of two high-accuracy transformers, identified as amplifier-aided two-stage transformers, are described. Each operates from 50 Hz to 10 kHz, supporting burdens up to 1 ¿. Self-contained ratios span from 5/5 to 100/5, with a rated secondary current of 5 A. Results indicate the errors at 10 kHz are within 30 and 15 ppm for the respective transformers, decreasing to less than 1 ppm at 1 kHz. Analysis of high-and low-frequency errors is presented, as well as a detailed description of a capacitance trimming technique effecting a factor-of-ten reduction of capacitive errors. Also described is a relatively simple step-up calibration system for determining the transformer errors. Calibration results are included. View full abstract»

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  • A New Digtal Method for DC-Current Measurement with Floating Input

    Page(s): 346 - 349
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    This paper describes a new method for direct-current measurement without direct connection to the circuit under test, producing a time-coded indication. A magnetizable ring core with three separate windings is driven to positive and negative saturation by a triangular alternating current. The voltage induced in the detector winding is differentiated. The time interval between two zero-axis crossings of the differentiated voltage is a measure of the current in the measuring winding. Investigations on an experimental setup showed that high resolution and sensitivity and small error of linearity can be achieved. Furthermore the internal resistance can be kept small. View full abstract»

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  • Electronic Method with Direct Time Encoding for Precision Measurement of Electric Power over a Wide Range of Frequency

    Page(s): 350 - 353
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    The principle of power measurement by thermal means has the advantage of a very large bandwidth and gives the possibility to realize time or frequency encoding in a simple way. The new method described is based on a known operation using special thermal converters with several heaters. The multiple heating, however, is done by a multiplexing operation on single-heater converters. It is shown that, by means of this principle, a power meter can be set up enabling precision measurement in a wide range of frequency. The measurement of real power in polyphase systems is another application of the same principle. View full abstract»

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  • An Evaluation of the Three-Voltmeter Method for AC Power Measurement

    Page(s): 353 - 357
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    The accuracy and frequency response limitations in the present square-law responding laboratory wattmeters have promoted the search for alternate methods of ac power measurement using electronic instrumentation. The three-voltmeter method is based on an old principle of operation implemented by new analog circuitry. Results of the tests reported here show a precision of power calculation with 0.01 percent error at frequencies below 5 kHz. A unique test procedure is described for the comparison of the three-voltmeter device and a time-division multiplier wattmeter operating at zero power factor. View full abstract»

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  • Low-Frequency Electrical Signal Measurement by Electrooptical Methods

    Page(s): 358 - 360
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    An analog system for the optical telemetry of voltage or current information using light-emitting diodes (LED) is described. Errors resulting from variations in the optical coupling efficiency are minimized because the light emitted by the LED contains the signal to be measured superimposed on a fixed intensity beam controlled by a reference zener diode. The nonlinearity of the LED is overcome by using part of its emitted light to control the feedback current to an operational amplifier that supplies the signal to the LED. The prototype system developed has a total error of approximately 0.2 percent of the input signal. View full abstract»

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  • NPL Calculable Capacitor

    Page(s): 361 - 365
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    The NPL calculable cross capacitor is designed to provide a standard of the highest accuracy. It has a vertical axis and the length is determined by central guard tubes. The length is altered by axial displacement of the lower tube and the change is measured interferometrically. This paper describes the construction and performance of the capacitor and records the results of the initial measurements; the uncertainty of these is of the order of 10-7. View full abstract»

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  • Phase-Angle Characteristics of Cross Capacitors

    Page(s): 365 - 368
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    It has been found that under proper conditions thin dielectric films on the electrodes of certain types of cylindrical cross capacitors tend only to produce equal and opposite contributions to the phase angles of the two cross capacitances. To a lesser degree, this same type of cancellation effect has been found to be associated with toroidal cross capacitors. View full abstract»

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  • An Optimized Design for a Low-Frequency Inductive Voltage Divider

    Page(s): 368 - 372
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    A theoretical investigation of the causes of error in multidecade two-staged inductive voltage dividers (IVD) has been made and from this an optimized design for the frequency band 10-400 Hz has been evaluated. A three-decade divider rated at 0.6 times frequency has been constructed and calibrated and the errors of voltage division do not exceed the design limits of 5 × 10-9 of input. View full abstract»

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  • Absolute Measurement of Voltage by an Electrostatic Energy-Changing Method

    Page(s): 372 - 375
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    A new method for an absolute measurement of voltage is given. It is based on the phenomenon that, when one electrode of a capacitor supplied with a constant voltage is moved, the amount of the change of the electrostatic energy stored in the capacitor is equal to the work required for this movement. A prototype of an apparatus to be used in this method was prepared and its performance has been examined. In an ideal case, it is considered possible to determine the voltage with an accuracy of a few parts in a million with this apparatus. View full abstract»

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  • A Noncontacting Magnetic Pickup Probe for Measuring the Pitch of a Precision Solenoid

    Page(s): 376 - 379
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    The magnetic-field gradients produced by a current sequentially activating a few turns of wire of a precision solenoid are used to measure its pitch. The position of the activated portion of wire can be resolved to 0.1 ¿m. Preliminary results are found to be in agreement with an earlier measurement using a contacting probe to within the uncertainty of the latter determination. This new technique reduces many of the difficulties associated with conventional pitch measuring schemes and at the same time provides a method of obtaining increased accuracy. View full abstract»

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  • Automatic Measuring System for a Control of Standard Cells

    Page(s): 379 - 384
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    The automatic measuring system developed in the Electrotechnical Laboratory to monitor standard cells requiring a lot of measurements is described. It is composed of a scanner, an integrating-type digital voltmeter, a programmer or minicomputer, etc., and carries out the data acquisition and processing for a maximum of 200 cells. The difference in EMF of two cells is measured precisely. To reduce the effect of the induced EMF in the scanner, a delay unit is provided, and procedures minimizing errors and evaluating random errors have been adopted. In the on-line version of system, a great part of the data processing is done during the delay and integrating time of digital voltmeter. Applying this system to the measurement of standard cells, a precision of the order of 0.1 ¿V has been obtained. View full abstract»

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  • Introduction to Saturated Optical Absorption

    Page(s): 384 - 387
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    Saturated absorption techniques are being used increasingly often to measure optical resonances having such narrow bandwidths that they would otherwise be obscured by Doppler broadening. The principle underlying these techniques is reviewed using four simple thought or "gedanken" experiments. A rudimentary explanation is based on Bennett's " hole-burning" picture. Two configurations of typical saturated absorption experiments are described. One illustrates absorption outside and the other inside of a laser cavity. The intracavity technique is recommended for weak absorbers and when especially simple compact apparatus is needed. For most other experiments, the gaseous absorber is better located outside the laser cavity. 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