DOI:10.1049/pi-2.1951.0183

出版商:IEE    

年代:1951

数据来源: IET

DOI:10.1049/pi-2.1951.0184

出版商:IEE    

年代:1951

数据来源: IET

摘要:

With new principles defined as first applications of the laws of physics, the paper reviews some of the new principles of electrical measurement which have come into use during recent years. The background upon which these methods have developed is recalled and commented upon.The economic reasons for and the implications in the use of new principles, and the methods involved thereby, are also reviewed.

DOI:10.1049/pi-2.1951.0185

出版商:IEE    

年代:1951

数据来源: IET

摘要:

After defining the scope of the paper and discussing the relation of the design of the display of the reading to the design of the instrument as a whole, some of the special characteristics of the human eye and brain which affect seeing power are described.The various factors affecting the presentation of the instrument reading which have to be considered by the designer are dealt with in detail, and reference is made to subjective tests carried out at Cambridge University and elsewhere.A brief display specification for laboratory and industrial instruments is then given with comments and is followed by a description of recent developments in presentation technique. Finally, possible future developments with a view to improving the readability of instruments are outlined.

DOI:10.1049/pi-2.1951.0186

出版商:IEE    

年代:1951

数据来源: IET

摘要:

The difference between “international” and “absolute” electrical units is explained, and the reason for the change made in 1948 from one system to the other is given. The uncertainty of the electrical units defined in terms of length, mass and time is estimated to be about 20 parts in a million, although the accuracy of comparison of electrical quantities may be as high as one part in ten million. The loss of accuracy in the measurement of voltage, current and power when transferring from direct to alternating current is explained: it is estimated that these quantities cannot be measured at power frequencies to better than one part in 10000.

DOI:10.1049/pi-2.1951.0189

出版商:IEE    

年代:1951

数据来源: IET

摘要:

The performance limits of the best types of electrical instrument are considered. The errors from unknown causes have, in general, been reduced to negligible values in specially adjusted instruments, and in this sense, the design of electrical instruments may be said to have achieved finality. However, there is still room for improvement in the reduction of errors from known causes and in the raising of the level of the commercial product, as distinct from the specially adjusted laboratory one.The defects found in instruments submitted for test by the National Physical Laboratory are described in some detail; some of the most important of these are scale errors, level errors and sticking of the movement. There is, however, a very large number of other defects, ranging from irritating trifles to serious faults, many of which could be eliminated by more careful inspection of the instruments by the manufacturers.The design of instruments might be improved with a view to reducing errors from known causes. One error, in particular, which is becoming of increasing importance with modern applications is the frequency error, which is usually small in the best instruments at power frequencies but may become so large at moderately high audio frequencies as to render the instrument useless. The frequency errors of a number of types of instrument are considered, and the improvements made possible by simple types of compensation are demonstrated.

DOI:10.1049/pi-2.1951.0190

出版商:IEE    

年代:1951

数据来源: IET

摘要:

The paper outlines the merits of a number of high-permeability magnetic alloys under a variety of conditions likely to be met in instrument practice. The properties found with d.c., a.c. and combined a.c./d.c. operation are indicated, and recommendations are made for the best alloy to be employed in particular circumstances. Information is given on the spread of the magnetic characteristics of Mumetal spiral cores produced on a commercial scale.A Section of the paper is devoted to a.c. permeability and losses of spiral cores, rings and particular assemblies of laminations, and the adverse effect of joints in the magnetic circuits is clearly demonstrated.A method of predicting harmonic distortion in small transformers and chokes is described briefly, and curves of distortion-coefficient variation with induction for a number of nickel-iron and silicon-iron alloys are given. Non-uniform flux distribution has a marked effect on harmonic generation, and this is studied in detail; a number of anomalies are examined and practical recommendations are made.Magneto-striction and the variation of magnetic properties with temperature are treated, together with a brief comparison of permeability and relative costs of a number of magnetic materials.The paper includes curves which will be of reference value to designers.

DOI:10.1049/pi-2.1951.0193

出版商:IEE    

年代:1951

数据来源: IET

摘要:

The paper comprises a general discussion of the properties of insulating materials used in electrical instruments, with emphasis on the new synthetic organic materials. Values of dielectric constant and loss angle are tabulated. The structures of the main polymers of electrical interest and the relations between structure and electrical properties are briefly indicated. The advantages in instrument design of using small amounts of high-quality insulating materials, rather than larger amounts of the older conventional materials, are discussed with reference to the properties of the newer synthetic materials. The electrical behaviour of composite materials is discussed chiefly with reference to moisture absorption and electric strength. A Section deals with miscellaneous new materials for sealing against moisture, for cooling by an immersion medium, and for adhesive purposes. A short Bibliography is given, indicating the more important collections of information on insulating materials.

DOI:10.1049/pi-2.1951.0194

出版商:IEE    

年代:1951

数据来源: IET

摘要:

The paper describes the present position regarding some components used in electrical instruments from the aspect of reliability and functional suitability under severe working conditions. Most of the components discussed are considered from the point of view of the Services, where a high standard of performance is required even under extreme climatic conditions. Details are given of the shortcomings of some of the present-day components and of the effort which is being directed to overcome them by the exploitation of new materials, new processes, improved design and better methods of manufacture.In addition to the commonly used components, such as resistors, capacitors and transformers, mention is also made of a precision variable inductor, and Sections dealing with meters, electronic valves and quartz-crystal units have also been included.

DOI:10.1049/pi-2.1951.0195

出版商:IEE    

年代:1951

数据来源: IET

摘要:

The paper is a review of the techniques used in the detection and measurement of very-short-wave radiations (X-rays and γ-rays) and nuclear and cosmic particles (α-particles, β-particles, protons, neutrons and mesons).The radiations and particles are classified under three headings—X-rays and γ-rays, charged particles, and uncharged particles; in each case an account is given of the more important measurable quantities (e.g. energy,W, flux of radiation, Φ, radiation dosage,r, etc.) and the physical basis of the method of measurement involved. The examples chosen to illustrate these techniques are process instruments developed at the Atomic Energy Research Establishment to provide continuous monitoring of α- and β-activities in solution. In the α-activity monitoring instrument the pulse technique is used for recording individual particles, whereas in the β-activity instrument the mean rate of ionization in an ionization chamber is measured as a direct current. Complete descriptions are given of both instruments, together with details of the performance characteristics obtained.The paper ends with a discussion of nucleonic-instrument design, and a number of aspects receive special mention, namely sourcedetector geometry, detectors in assay instruments, special problems associated with portable instruments and, lastly, materials and finishes for radioactive-contamination monitoring instruments.

DOI:10.1049/pi-2.1951.0198

出版商:IEE    

年代:1951

数据来源: IET