Electricity: measuring and testing – Magnetic – Magnetometers
Patent
1993-06-28
1995-11-28
Snow, Walter E.
Electricity: measuring and testing
Magnetic
Magnetometers
32420713, 25022714, G01B 714, G01B 902, G02B 514
Patent
active
054711398
ABSTRACT:
A fiber optic line magnetometer is used in a railway block detection system for detecting the presence of a train, or a portion of a train, within a predetermined block. The fiber optic line magnetometer is positioned in the center of the tracks and runs parallel to the tracks for the entire length of the block. The fiber optic line magnetometer includes a sense arm and a reference arm, each of which includes a fiber optic cable for carrying a light originating from a signal source. Magnetostrictive elements connect to the fiber optic cable in the sense arm and change the light path length when external magnetic fields are applied thereto. The light exiting from the sense arm and the reference arm are compared, and in the event the fringe shifts in the compared light exceeds predetermined thresholds, a detection control signal is generated. Non-magnetostrictive elements, which are sized to have the same thermal temperature expansion characteristics as the magnetostrictive elements, are attached to the fiber optic cable of the reference arm.
REFERENCES:
patent: 4376248 (1983-03-01), Giallorenzi et al.
"Elements of Railway Signalling", Pamphlet 1979, General Railway Signal, P.O. Box 20600, Rochester N.Y.
"Magnetic Thin-Film Magnetometers of Magnetic-Field Measurement", H. R. Irons and L. J. Schwee, IEEE Transactions on Magnetics, vol. MAG-8, No. 1, pp. 61-65, Mar. 1972.
"Optical Fiber Sensor Technololgy", T. G. Giallorenzi, J. A. Bucaro, A. Dandridge, G. H. Sigel Jr., H. Cole, S. C. Rahsleigh, and R. G. Priest, IEEE Journal of Quantum Electronics, vol. QE-18, No. 4, pp. 626-665, Apr. 1982.
"Recent Developments in Fiber Optic Magnetostrictive Sensors", F. Bucholtz, D. M. Dagnenais, K. P. Koo, S. Vahra, Proc. S.P.I.E.--Int. Soc. Opt. Eng. (USA), vol. 1367, pp. 226-235 (1991).
"Safety and Automatic Train Control for Rail Rapid Transit Systems", Jul. 1974, Report No. DOTTSC-OST-74-4.
"The Impact of High Temperature Superconductivity on Squid Magnetometers", J. Clarke and R. H. Koch, Science, vol. 242, pp. 217-223 (14 Oct. 1988).
EMS Development Corporation
Snow Walter E.
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