Outokumpu Oy

Erkki Ilmari Leinonen

Erkki Sakari Kiuru

Kari T Aittoniemi

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

In a stabilized voltage source having an actual-value voltage gauge which is temperature dependent, the overall temperature stability of the voltage source is improved by providing a reference-value voltage with an adjustable temperature coefficient, said temperature coefficient being so adjusted that it substantially compensates for the temperature dependence of the actual-value voltage gauge within the temperature range used. The reference voltage having an adjustable temperature coefficient is preferably obtained by combining a first voltage which is essentially independent of temperature with a second voltage being strongly dependent on temperature, the degree of mutual influence of said combined voltages being regulated to adjust said temperature coefficient.

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Vantaa, Finland

Erkki Ilmari Leinonen