摘要:

There is at present no absolute standard method of measurement by which the high voltages now in common use may be compared. The paper gives an account of such a method in which the polarization of a metallic ellipsoid of revolution, suspended by an insulating fibre between vertical circular pole-plates, is observed. The dimensions and proportions of the ellipsoid and of the horizontal field were determined with high accuracy, and the magnitude of the electric gradient on the axis of symmetry of the instrument was calculated for given applied voltages. The working formula of the instrument isF=K(n2−n20)frac12;, whereFis the field strength,ka constant found from the dimensions,nthe number of swings per second of the ellipsoid with the field on andn0with it off. The influence of the spacing of the plates, of shielding the ellipsoid, of gas pressure and temperature, was examined, and the readings of the instrument were compared with Whitehead and Castellain's sphere-gapdeterminations of voltage. As a combined check on the accuracy of their readings and those of this instrument, a value of the ratiocof the electromagnetic to the electrostatic units of quantity is obtained which agrees with the best previous results. It is concluded that continuous measurements of voltages up to 200kV can be made with the precautions indicated in the paper, to an accuracy of at least 3 parts in 1 000, the constant of the instrument depending upon the value accepted for the ratioc

DOI:10.1049/jiee-1.1932.0064

出版商:IEE    

年代:1932

数据来源: IET

摘要:

The paper deals briefly with some of the more important developments in design and use of cathode-ray oscillographs. Methods of increasing the photographic or recording sensitivity are first considered, particular attention being given to (a) focusing the cathode-ray stream, (b) increasing the sensitivity of the photographic film, (c) the use of phosphorescent materials as a means of increasing photographic sensitivity and of facilitating “external” photography, and (d) increasing the exciting voltage and consequently the kinetic energy andpenetrating power of the cathode rays. With regard to (d), particular a ttention is paid to Lenard's observations on the penetrating power of high-velocity cathode rays and the application of his results to the design of high-voltage oscillographs fitted with a “window” for direct external photography.Referring to the technique of recording by cathode rays, consideration is given to the various methods of generating a “time” axis and to methods of voltage subdivision. The paper concludes with a section dealing with the recording of isolated electrical impulses.

DOI:10.1049/jiee-1.1932.0068

出版商:IEE    

年代:1932

数据来源: IET

摘要:

The rapid development of the hot-filament type of cathode-ray tube is outlined, andvarious sources of error which are encountered in its use as a measuring instrument are discussed, including errors inherent to the tube, especially those due to the effect of gas conduction, then errors of manipulation and those due to external influences are reviewed.Recording is next dealt with, including photographic methods, and various methods of calibrating are considered. The chief part of the paper, however, deals with what is known as the “threshold effect”, a quantitative examination of which is given, together with graphs showing its relation to the various variables, such as frequency and the effect of resistance in series with the deflecting plates.Suggestions are put forward as to the cause of the threshold effect, and the paper concludes with recommendations for accurate working.In an Appendix particulars relating to the latest pattern of low-voltage tube are given, and its sensitivity is discussed.

DOI:10.1049/jiee-1.1932.0069

出版商:IEE    

年代:1932

数据来源: IET

摘要:

In the study of electromotive forces varying with time, the electromotive force under examination is caused to modulate similarly and simultaneously two voltages which are applied in quadrature to the deflecting plates of a cathode-ray oscillograph. The resultant screen-image on the oscillograph consists of a circular time-base, on which are superposed radial deflections delineating the wave-form and the time relation ships of the applied electromotive forces.

DOI:10.1049/jiee-1.1932.0072

出版商:IEE    

年代:1932

数据来源: IET

DOI:10.1049/jiee-1.1932.0075

出版商:IEE    

年代:1932

数据来源: IET

摘要:

The paper describes the improvements in the technique of radio-receiver testing that have been made at the National Physical Laboratory. The arrangements now used for this purpose having been described in detail in Part 1, a proposed specification of methods of testing broadcast receivers is given in Part 2, together with experimental results obtained on such receivers. This specification is examined as to its applicability to the relative comparison of widely different types of receivers, and a classification is suggested so as to diminish the number of tests which it is necessary to make in order to assign a figure of merit to a particular receiver.

DOI:10.1049/jiee-1.1932.0077

出版商:IEE    

年代:1932

数据来源: IET

摘要:

An apparatus is described for measuring relative field intensities of wireless waves of the order of 20 metres, and the results of a series of measurements taken with it on wavelengths of approximately 25 metres for distances of from 200 ft. to 60 miles from the transmitter are shown as“Intensity/Distance” curves. For distances greater than 2 miles the decrease of intensity is found to be approximately proportional to the inverse square of the distance as predicted by the theory of Sommerfeld. For shorter distances, however, the curves are much straighter than predicted by theory. This is attributed to penetration of the waves to layers of higher conductivity below the surface. This is supported by the increase in the variations in attenuation with change of surface observed on a wavelength of 18 metres and by measurements on the “tilt” of the electric vector of the wave-front.In all cases, marked changes in intensity and attenuation were found to occur with apparently slight changes of surface and slope of the ground.

DOI:10.1049/jiee-1.1932.0080

出版商:IEE    

年代:1932

数据来源: IET