摘要:

Existing acceptance and quality tests are discussed. War conditions brought increased inspection and an urgent need to classify quality. Most tests were found to be limited in application, or of doubtful value, owing to the wide scatter of results. Abrasion and electrical breakdown are considered in greater detail and a limited enquiry into the pinhole test for enamelled wire is described. The difficulties of chemical tests by the purchaser on textile coverings make such tests impracticable as a control. There is a need for some new improved tests and for appreciation of the limitations of the existing ones.

DOI:10.1049/pi-2.1951.0143

出版商:IEE    

年代:1951

数据来源: IET

摘要:

The theory, construction and use of an electrostatic wattmeter suitable for the measurement of the losses in magnetic materials subjected to alternating magnetization are described. Details are also given of amplifiers for use in conjunction with the wattmeter, particularly at low frequencies and low flux-densities.Selected experimental results are given to illustrate the use of the equipment with a variety of magnetic materials, over a frequency range of 25 c/s to 25 kc/s.

DOI:10.1049/pi-2.1951.0146

出版商:IEE    

年代:1951

数据来源: IET

摘要:

Various methods of connecting a screened twin cable and an earthed measuring instrument are examined. It is shown that the cable characteristics can be most easily and accurately measured when the connections are such as to produce a nearly symmetrical potential distribution in the cable. In this condition, the impedance measured depends almost entirely upon the constants of the twin system and is only slightly influenced by the earthed system formed by the inner conductors and the screen.Capacitance, attenuation and phase unbalance are discussed. It is shown that a method in which connections are made to both ends of the cable is particularly useful with unbalanced cables, for it automatically takes the average of the two readings which would otherwise be required.

DOI:10.1049/pi-2.1951.0149

出版商:IEE    

年代:1951

数据来源: IET

摘要:

The paper considers the criteria of sensitivity and stability required for the determination of the dielectric constants of gases, and discusses the methods of measurement which have been used in relation to these criteria. The heterodyne method—which has been the most widely used—is considered to fail to meet the requirement of stability; other methods having the necessary stability are insufficiently sensitive. It is considered that the necessary stability and sensitivity can be achieved by the use of an a.c. bridge, a suitable design of which is discussed. Results are given to illustrate the performance of such a bridge, and it is shown that a change of capacitance of one part in six million is detectable, whilst the capacitance drift is normally less than one part in 106per hour. This drift is probably due to atmospheric changes. Results of the measurement of dielectric constants of several gases and of water vapour are given.

DOI:10.1049/pi-2.1951.0150

出版商:IEE    

年代:1951

数据来源: IET

摘要:

A consideration of several methods which have previously been used in the investigation of surge phenomena leads to a review of some of the design requirements for the instrument described in the paper, which includes a simplification of design by the use of Post-Office-type counters. The design of this surge counter is then considered in detail, and its operation explained, in conjunction with block and circuit diagrams:a diagram of a recording obtained automatically by the instrument is shown.

DOI:10.1049/pi-2.1951.0151

出版商:IEE    

年代:1951

数据来源: IET

DOI:10.1049/pi-2.1951.0152

出版商:IEE    

年代:1951

数据来源: IET

DOI:10.1049/pi-2.1951.0154

出版商:IEE    

年代:1951

数据来源: IET