Outokumpu Oy

Kari T Aittoniemi

Erkki Sakari Kiuru

Erkki Ilmari Leinonen

Aatu V Lappalainen

Ari T Jarvi

Kalevi Savolainen

The invention relates to a metal detector for detecting metal objects in the material passing through the apparatus by means of a magnetic field induced by eddy currents. According to the invention, in the area between the transmitter coil system (1, 6) and the receiver coil system (3, 7) of the metal detector, there is installed at least one electrically insulated but electroconductive and/or magnetic element (2, 4, 5) in order to change the sensitivity distribution of the metal detector.

Metal detector

The invention relates to a method for detecting metal objects, particularly to improving discrimination in a metal detector, where at least two responses are defined for metal objects passing through the metal detector. According to the invention, the correlation of the responses is examined within a determined time period in the metal detector, and at least one parameter is formed of these responses in order to define the group of objects that caused the response.

Improving the discrimination of an impulse technique metal detector by

The invention relates to a method and an apparatus for detecting metal objects in a metal detecting apparatus using impulse techniques. The metal detector comprises a compensation circuit arranged in between the transmitter system (13) and the receiver system (14) in order to compensate the mutual inductance between the transmitter (11) and the receiver (12). The compensation circuit is advantageously operated so that the signal caused by the metal object in this detector is measurable during both at least two measuring sequences (21,22) located within the range of the cut-off peak of the transmitter current and during at least one measuring sequence (23) located outside the range of the cut-off peak of the transmitter current.

Impulse induced eddy current type detector using plural measuring

The apparatus of the invention comprises at least two transmitter coils (3) and a respective number of receiver coils (4). The transmitter coils (3) and the respective receiver coils (4) are placed in a crosswise position with respect to each other so that the primary fields created by the transmitter coils (3) are divergent.

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Espoo, Finland

Kari T Aittoniemi