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Measurement of attenuation at 400 MC is required in the JAN Specification for R. F. Cables. The Naval Research Laboratories developed' a test set for this purpose which is undoubtedly familiar to many companies manufacturing cable. Fig. 1 shows a schematic diagram of this test set. The theory and operation of the set is as follows: The generator and its coupling loop can be replaced by the series...
This review of dielectric measurements is confined to the measurement of the complex dielectric constant of dielectrics, with no consideration whatever for the measurement of dielectric strength. Only measurement technique will be considered, with no reference to specific dielectric properties except as their magnitude and variation directly affect the technique. The conditions under which measurements...
According to the classification of Hague, this bridge belongs to the class of networks containing only resistance and capacitance and employs the parallel resistance method for comparing capacitors.
This study is aimed at the development of rubber insulations completely resistant to attack by soil microorganisms. The failures caused by soil microbes are minute Regions of low insulation resistance and dielectric strength surrounded by sound insulation.
A modern high-voltage aerial cable has, around its copper conductor, a high-voltage synthetic rubber insulation such as, Butyl; metallic shielding (copper tape, tapes, or braid); and a protective jacket overall such as, Neoprene. Two types of terminals for such cable are in use: the time-honored pothead with a compound-filled cast metal bell and porcelain insulator, and a splicer-made field termination...
The electrical properties of titanium dioxide semiconductors have been under study for several years.1,2,3,4 In general, however, the previous studies were only of the electrical conductivity of ceramics so that little information about the properties of the rutile lattice is available. Recently, however, synthetic rutile crystals have been placed on the market∗, and an investigation of their electrical...
Breakdown tests on commercial sheet insulation are usually made with disc electrodes with either square or round edges1. The breakdown is often initiated at he electrode edges where the electrical stress on the immersion medium is high, even when liquid immersants are used.
In a recent study on the change of dielectric constant as a determination of the progress of crystallization of an inorganic compound, a great deal of difficulty had been experienced. The cause lay in the high and continually changing dielectric constant of the specimen and in the necessity of involving the use of a series capacitor and a container both of which had different dielectric constants...
The measurement of dielectric properties in the microwave band is usually accomplished by placing the sample in a waveguide or resonant cavity. Free-space methods, while lacking the general versatility of waveguide techniques, exhibit certain advantageous features: the problem of maintaining a precision fit between the sample and the guide is avoided; certain structures, for example, “honeycomb” materials...
Previous work carried out in this laboratory has indicated the desirability of further studies of the correlation between dielectric relaxation phenomena, molecular structure and viscosity. Measurements have been carried out on solutions of the nearly spherical t-butyl chloride and methyl chloroform molecules and the long n-tetradecyl bromide molecule in two non-polar solvents, n-heptane and a viscous...
A calculation of the static dielectric constant of a crystalline — dipolar material of simple structure is outlined. It is assumed that the dipoles are arranged in a simple cubic structure (NaCl type) and that ordering forces between them depend on the shape of the molecule and are exerted between nearest neighbors only (short range forces). Each dipole is assumed to have two possible positions 180°...
Liquid and plastic polytrifluoromonochloroethylene polymers exhibit similar electrical behavior as a function of temperature and frequency. As the temperature is lowered, one passes from a single phase (either solid or liquid depending on average molecular weight) to a two-phase state characterized by the appearance of crystallites in the material. The temperature at which crystals appear depends...
In 1936, G. Groetzinger reported apparent increases (See Table I) of as much as 71% in the thermal conductivity of beeswax electrets (See Table II) over that measured for unelectrified beeswax. In view of the technical advantages of such a property, we decided to repeat these experiments. Groetzinger1s experimental conditions were reproduced, but no difference between the thermal conductances of electret...
Failure of electronic apparatus under conditions of high humidity and temperatures conducive to the growth of molds focused attention upon the role of molds in deterioration. Early investigation of this problem solely by cultural biological techniques resulted in extensive use of lacquers and varnishes containing fungicides as coatings for electronic equipment and components.
During the war the Armed Services experienced a high rate of failure of electronic equipment in tropical service. Upon examination, much of this equipment was found to be covered with fungus growth. It was recognized that this fungus growth occurred at high humidity. The direct contribution of moisture itself to the failure of electronic equipment was often overlooked and fungus growth alone was blamed...
Those familiar with the history of organic insulating materials are aware of the fact that within the last thirty years, materials from natural sources are gradually being replaced with synthetic materials. The result of such a substitution is usually a product with consistently better and more controllable properties. This type of progress was made possible by the many developments in the synthesis...
In the course of an investigation of the electrical properties of pure high polymer materials, measurements of the dielectric constant and loss factor of Poly-vinybutyral (Butvar), Polystyrene, Methyl methacrylate, and a copolymer of the latter two materials were made over a frequency range from 60 c/s to 1000 Mc/s. An effort was made to improve the accuracy of these determinations to facilitate the...
There are several important factors which determine the minimum safe leakage distance for insulation. However, two basic factors are (a) the magnitude of surface leakage currents, and (b) the effects of these currents on the insulation. The magnitude of this current depends upon the characteristic of the surface, surface contamination and the voltage gradient. Since the power loss caused by the leakage...
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