Electromagnetic detector responsive to a modification of a magnetic field
AssigneeThomson-CSF
InventorsJean-Raymond Narbaits-Jaureguy, Henri Billottet, Pierre Granier
Life of this patent
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Abstract
An electromagnetic detector designed to monitor road traffic, responsive to a modification of an electromagnetic field produced by the presence of a metallic mass in the vicinity thereof, comprises a metal base on which are disposed a transmitting coil creating a field and a receiving coil whose axis deviates from the perpendicular to the base. The receiving coil detects a measuring field created by the currents induced in the base by the transmitted field. The processed signal is the resultant of the signal produced by the presence of a metallic mass in the transmitted field and by the signal due to the measuring field.
Claims21
An electromagnetic detector responsive to the proximity of a metallic mass, comprising:
- a metallic base having a flat upper surface;
- a supply of alternating current;
- transmitting means on said base, including a first coil with an axis parallel to said surface, connected to said supply for generating a surrounding electromagnetic field inducing eddy currents in said base;
- receiving means on said base, including a second coil with an axis inclined to said surface, spaced from said transmitting means and positioned to pick up a measuring field produced by said eddy currents together with a component of the surrounding field as modified by a metallic mass in the vicinity, thereby generating a resulting signal varying with the presence or absence of such mass;
- and
- processing means connected to said receiving means and to a source of reference oscillation energized from said supply for evaluating said resulting signal to indicate the proximity of said mass.
Dependencies are inferred from the claim text.