Identifier: exp142673001918306306unse (find matches)
Title: An experimental study of the fahy permeameter
Year: 1918 (1910s)
Authors:
Subjects: magnetism measurements and use of instruments/ B8000 Power systems and applications
Publisher: National Bureau of Standards
Contributing Library: NIST Research Library
Digitizing Sponsor: NIST Research Library

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ridge.On this yoke is a winding with which a mmf is produced opposingthat to be measured. When the needle indicates a balance themmf in ampere turns is equal to the product of current and turnsin this winding. Iliovici ® has described a permeameter in which « Chattock. Phil. Mag., 24. p. 94: 1887.* Rogowski and Steinhaus, Archiv fiir Elektrotechnick, 1, p. 141; 1912. * Goldschmidt, Electrician, 54, p. 207; 1904.Iliovici, Bull. Sec. Int. des Elec. 3d ser., S, p. 581; 1913. BurrowslSanford J Fahy Permeameter 271 he uses a yoke with a test coil wound on it to detect a differenceof magnetic potential. In this apparatus compensation is madefor yokes and joints which is indicated by zero potential betweenthe ends of the specimen. Goltze^^ published data giving the resultsof permeability tests on a number of specimens magnetized betweenthe poles of an electromagnet. He used an arrangement of theform described by Chattock and Rogowski and Steinhaus for thedetermination of magnetizing force.
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Fig. 2.—Magnetic and electrical circuits in their simplest form The Fahy permeameter, which is the subject of the presentpaper, utilizes this latter principle. A short description of the ap-paratus has already been published. II. THEORY The basis of operation of this instrument is apparent from aconsideration of Fig. 2, which shows the circuits of the instrumentin their simplest form. The apparatus is H-shaped, with two testcoils. Ho and H^, spanning the free ends of the H and a magnet-izing coil, M, wound on the crosspiece of the H. By reason of the symmetry of the two parallel magnetic circuitsthus formed it is evident that the magnetizing coil produces the 1 Goltze, Archiv fiir Elektrotechnik, 2, p. 303; 1914. Kahy, El. World, 69. p. 315; 191 ^ 272 Bulletin oj the Bureau of Standards (Voi.j4 same amount of flux in the two equal coils Ho and H^ and thateither one may be used to measure the mmf drop between theyokes, and from this value the mean magnetizing force may becalculated.

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