Precise Electrical Measurements Research Articles

Influence de l'adsorption métallique sur la résistivitéélectrique de films minces d'or

Precise electrical resistance and thickness measurements are used to study metallic adsorption on thin gold films under ultra-high vacuum conditions. The large variations of resistance observed for impurity coverage lower than a monolayer are interpreted by classical size effect. Adsorption of various “sp” and transition metals have been investigated. We report here some typical plots showing the resistance increase of gold films about 250 Å thick versus metallic impurity coverage. Different informations obtained from these curves are discussed. The adatom resistivity at very low coverage is determined experimentally; its variations versus valence impurity are similar to the bulk impurity resistivity; the role of the adsorption site is also examinated. In some cases the overlayer growth mechanism can be determined, specially when it is of the Frank-van der Merwe type; in this case, the influence of temperature on the structure of the first monolayer has been investigated. For coverage greater than a monolayer, some examples of intermetallic compound formation or intergranular migration revealed by electrical resistance measurements, X-rays and electron microscope observations are given.

SQUIDs and their applications

SQUIDs are a class of very sensitive superconducting measuring devices, whose operation is based on flux quantization and the Josephson effects. After a brief summary of these effects the principles of operation of single and double Josephson junction SQUIDs are dealt with in some detail, including noise processes and estimates of the ultimate sensitivity attainable. Applications of these devices in a wide variety of fields including precise electrical measurement, thermometry, magnetic properties, relativity physics, geophysical measurement and biomagnetism are dealt with.

Influence de l'absorption d'atomes de plomb sur la résistance électrique de films d'or

Precise electrical resistance and thickness measurements are associated to study lead adsorption on gold films in ultra-high vacuum. Fuchs' theory is used to interpret the large size effects observed when the lead deposit is less than one monolayer. At low coverages the ratio of electrical resistivity variation to lead concentration is independent of temperature and equal to 1.8 ± 0.1 microOhms cm/at%. With temperatures ranging from − 150 to + 150°C, the evolution of size effects is related to structural changes in the lead overlayer. A saturation in the diffuse scattering of conduction electrons by adsorbed adatoms is shown to occur when the lead deposit is about half a monolayer; this is used for comparing surface roughness of annealed and unannealed gold films. For lead coverage greater than a monolayer, an alloy identified by X-ray diffraction as AuPb 2 is formed. The electrical resistance variation is consistent with the thinning of the gold film by removing atoms which diffuse towards the free surface through the alloy layer.

Book Review: Precision Electrical Measurements in Industry

Book Review: Precision Electrical Measurements in Industry

Precision Coaxial Connectors in Lumped Parameter Immittance Measurement

Amid the concern surrounding the design and application of precision coaxial connectors for use in precise electrical measurements there is one area which has received very little attention. This has to do with the application of such connectors to measurements in the lumped parameter region. This paper points out significant sources of error in lumped parameter measurements which are attributable to connector uncertainties and shows how they can be greatly reduced through the application of precision coaxial connectors. Where these connectors are utilized in lunped parameter immittance measurements, extensions of frequency, magnitude, and accuracy are realized. Specific examples are discussed.

Electrical Conductance Cell Assembly for Precise Measurements with Carbonates, Oxides, and Fluorides up to 1000°C

A conductance cell assembly is reported of the capillary design with a cell constant sufficiently high to permit precise electrical conductance measurements with the standard type precision conductance bridge circuits. Important features are the use of single crystal grade MgO for construction of the capillaries that determine the resistance for the electrolyte in the conductance cell, and the use of such materials as gold, or gold-palladium alloy to construct the various other components of the cell that contact the molten salts. The suspension of the MgO crystal capillaries is of a novel design which permits removal of the capillaries from the assembly for inspection or cleaning, and yet holds these firmly and securely in position during measurements. It is shown that recently published values of electrical conductance for molten KCl and KNO3 may be used as standards for calibration of such cells at high temperatures.

Symposium. Precision Electrical Measurements. New York (15 East 40th Street): Philosophical Library, 1956. $12.00

Science EducationVolume 42, Issue 1 p. 94-94 Book Review Symposium. Precision Electrical Measurements. New York (15 East 40th Street): Philosophical Library, 1956. $12.00 First published: February 1958 https://doi.org/10.1002/sce.3730420126AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume42, Issue1February 1958Pages 94-94 RelatedInformation

Book Reviews: Precision Electrical Measurements. Proceedings of an International Symposium on Precision Electrical Measurements, National Physical Laboratory, 17-20 November 1954

Book Reviews: Precision Electrical Measurements. Proceedings of an International Symposium on Precision Electrical Measurements, National Physical Laboratory, 17-20 November 1954

Standards for electrical measurement

Precise electrical measurements are of fundamental importance to modern science and industry. This is true not only in the communication and power fields but in many other areas where the flexibility and convenience of electrical methods have made them almost indispensable for the measurement of nonelectrical quantities. Thus, while in textbooks energy is defined simply in terms of force and length or of mass and velocity, in actual practice the heat energy of fuels and the energy output of prime movers are universally measured to high precision by electrical methods. Likewise, the basic electrical units enter into the determination of nearly all the fundamental atomic constants, as well as into daily measurements of heat, light, color, strain, acceleration, displacement, and chemical properties.

Present Status of the International Electrical units

This paper summarizes the present legal standing and practical usage of the international electrical units, particularly as maintained in the United States. The international agreement reached in 1910 was provisional and requires some revision. Further investigations of the international standards, as well as of the absolute units, are urgently needed to put the system on a satisfactory basis for work of high precision. Legal authority to deal with electrical units has now been given the International Committee on Weights and Measures. This provides a permanent working organization through which international agreements can be reached and can be made effective throughout the world. When the committee takes up the question of electrical units for formal international adoption, it will have to decide whether to maintain as nearly as is practicable the values accepted at present or to revise them so as to accord with the fundamental c. g. s. system. With regard to primary standards, it will have to choose between the mercury ohm and silver voltameter, on the one hand, as against direct determination of the units by methods based on mechanical dimensions. The Bureau of Standards has under way several investigations planned to give a better technical basis for final decisions on-these questions. It is desirable also that they be discussed by those interested in making precise and accurate electrical measurements in order that all the advantages and disadvantages of the changes proposed may be given adequate consideration.