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Physical Science, Measurement and Instrumentation, Management and Education - Reviews, IEE Proceedings A

Issue 5 • Date July 1982

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Displaying Results 1 - 10 of 10
  • Piezoelectric devices

    Publication Year: 1982 , Page(s): 285 - 307
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (3127 KB)  

    The history of the discovery of piezoelectricity and its application in practical devices is traced from the late 19th century. The origin of the piezoelectric effect is outlined in terms of the symmetry of the materials, and Tables are given in which the electroelastic properties are listed for single crystals, ferroelectric ceramics and polymers which show the phenomenon. The applications of both the direct and inverse piezoelectric effect are considered in devices operating at frequencies from DC to greater than 100 GHz. Particular attention is paid to signal processing using piezoelectric substrates for surface acoustic waves, and to the use of quartz in crystal-controlled oscillators, but the whole range of devices from low frequency transducers, through acoustic and ultrasonic devices to VHF filters is discussed. View full abstract»

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  • Air-cored solenoid with a very small temperature coefficient of magnetic field

    Publication Year: 1982 , Page(s): 308 - 311
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (409 KB)  

    The design is given for a solenoid which produces a uniform magnetic field, the magnitude of which is almost independent of temperature changes. The results of measurements of the temperature coefficient of magnetic field produced by such a solenoid are given. It is shown that by adjusting the dimensions of the solenoid, the temperature coefficient can be made very small. View full abstract»

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  • Effects of phase-controlled switching on metering

    Publication Year: 1982 , Page(s): 312 - 315
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (293 KB)  

    In the common thyristor-controlled power ciicuit, the thyristor also functions as a convertor of power from the supply frequency to a very broad frequency spectrum. In general, a resistive load which is thyristor controlled has a inductive power factor, which approaches zero at large firing angles. Some of the harmonic power which is generated will be fed back to and redistributed by the supply network, and depending on their bandwidth this may or may not register on the users meters. If broadband meters are used, the harmonic power fed into the supply by a user will be subtracted from the fundamental power used. The power indicated by a broadband meter will depend on the mains supply impedance and on contributions of harmonic power from other users with similar nonlinear loads. The indicated power will therefore in general not be reproducible. View full abstract»

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  • Digital method of wavelength control in a feedback velocimeter

    Publication Year: 1982 , Page(s): 316 - 321
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (805 KB)  

    A digital method of wavelength control is described for a feedback velocimeter designed to measure the speed of steel strip. The measurement system, which has been described in an earlier paper, utilises the property of hysteresis of the steel strip and employs a wavelength-selective magnetic detector and a writing head upstream of the detector. Feedback causes a constant-wavelength magnetic pattern to be written onto the strip, making the frequency of the detector output a direct measure of the strip speed. In practice, slight variations in the wavelength occur which can be attributed to variable phase effects in the writing process. The advantages of further controlling the wavelength by digital means are described and the theory of the method is developed. The steady-state and transient performance of two different configurations is examined, one of which is clearly to be preferred. A measurement accuracy of better than ¿¿ 0.05% of actual speed is obtainable using this system in the presence of simulated disturbance such as might be expected in practice. View full abstract»

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  • Method for the absolute calibration of current transformers

    Publication Year: 1982 , Page(s): 322 - 327
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (657 KB)  

    The paper describes an absolute method for calibrating current transformers. The method, described as a build-up technique, involves calibrating a standard transformer first on its 5/5 ratio by comparing its primary and secondary currents directly in a differential circuit, and then on its 10/5 ratio by comparing it with two auxiliary 5/5 transformers with their primaries in quasiparallel and their secondaries in quasi-series to form a composite 10/5 transformer. The error of the combined transformers is the average of the errors of the individual 5/5 transformers, which themselves have been calibrated against the standard 5/5 transformer. The calibration is continued, thus building up to higher and higher ratios, and in the reverse procedure to lower ratios. Build-up steps using unequal ratios on the auxiliary transformers are also possible. Further, a method is described for calibrating a standard transformer at any given load current by combining the errors obtained at two lower currents. Measurements are made using a modified Arnold-type current-transformer testing set and relatively simple additional apparatus. The calibration is accurate to a few parts per million over a range of ratios from 0.05/5 to 160/5. View full abstract»

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  • Life expectancy and failure mechanisms of lapped synthetic tape impregnated with supercritical helium

    Publication Year: 1982 , Page(s): 328 - 331
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (673 KB)  

    Investigations into the life expectancy and failure mechanisms of cable models comprising layers of wrapped polymer tape impregnated with supercritical helium are described. Over the limited times of the tests the life law Ertt = constant is seen to apply, and, for the materials comprehensively tested, i.e high-density polythene, Valeron, polypropylene and polysulphone, n was found to be in the range 7 to 11. Valeron and polysulphone do not shatter when cold, and the extrapolated 30-year life stress was in the same order as the 1 pC inception stress, indicating that failure was due to the gradual erosion of the tapes by the butt-gap discharges. With polypropylene and polythene, small local shattering was observed in the mechanically highly stressed tapes examined immediately prior to breakdown. For those latter materials the life is determined by discharge erosion and shattering, and the 30-year life and inception stresses are not of the same order. Valeron is recommended as the best tape material for superconducting cable insulation; however, its AC working stress (1 pC) is less than the 10 MV m¿¿2 often used for dielectric design of superconducting cables. View full abstract»

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  • Effect of a symmetrically placed dielectric tube on the capacitance of a cylindrical cross-capacitor

    Publication Year: 1982 , Page(s): 332 - 336
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (440 KB)  

    The change in the cross-capacitance of a cylindrical cross-capacitor of circular cross-section when a dielectric tube is coaxially placed inside it is analysed. It is further shown that the analysis can be adapted to estimate a similar change in the case of a cylindrical cross-capacitor of the Thompson type. View full abstract»

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  • Use of the computer code PE2D in the electrostatic modelling of an electron-beam-generator/vacuum-diode interface

    Publication Year: 1982 , Page(s): 337 - 339
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (520 KB)  

    The computer code PE2D has been used to optimise the design of a compact, 500 kV, low-inductance vacuum-diode interface assembly for SPRITE, a sophisticated electron beam pumped exciplex laser system under construction at Rutherford Appleton Laboratory (RAL). Electrostatic modelling of various dielectric interfaces has been achieved in cylindrical symmetry under conditions not amenable to more traditional methods of electrostatic-field plotting. View full abstract»

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  • Electrocardiomultigraphimeter as a basic instrument for developing effective personal computing in cardiology

    Publication Year: 1982 , Page(s): 340 - 351
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1220 KB)  

    The question is posed as to whether personal medical computing can help significantly and efficiently in the development of `new¿¿ instruments. The scientific and economic criteria for considering an instrument as `new¿¿ are given; certain conditions are set out which, when confirmed, could lead to `new¿¿ instrumentation being developed from the personal computer, with better results than those produced by the microprocessor alone. In the early 1980s, appropriate conditions appear to apply in the area of electrocardiography. The `new¿¿ instrument proposed, called an `electrocardiomultigraphimeter¿¿, contains specific characteristics and performance which represent an advance on automatic diagnostic facilities, as well as the latest microprocessor-based electrocardiographs. Its field of application appears to be clinical research; its overall performance could be further extended to meet certain criteria of great significance for all medical departments geared to the care of many patients. The electrocardiomultigraphimeter hardware still presents certain snags - an example being the resolution of the unsatisfactory graphics capabilities. However, this is common to most current personal computers. View full abstract»

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  • General Assembly of the International Union of Radio Science

    Publication Year: 1982 , Page(s): 352 - 355
    Save to Project icon | PDF file iconPDF (702 KB)  
    Freely Available from IEEE