Commissariat &#xc0; L'&#xc9;nergie Atomique Et Aux &#xc9;nergies Alternatives

Nicolas Biziere

Claude Fermon

Myriam Pannetier

Thierry Sollier

Francois Vacher

François Vacher

A device for non destructive evaluation of defects in a metallic object () by eddy currents, comprises a field emitter () for emitting an alternating electromagnetic field at a first frequency fi in the neighborhood of the metallic object (), and a magnetoresistive sensor () for detecting a response signal constituted by a return electromagnetic field which is re-emitted by eddy currents induced by the alternating electromagnetic field in the metallic object (). The device further comprises: a driving circuit () for driving the magnetoresistive sensor () by a current at a second frequency fc which is different from the first frequency fi, so that the magnetoresistive sensor () acts as an in situ modulator; a detector for detecting a response signal between the terminals of the magnetoresistive sensor (); a filter for filtering the response signal detected by the magnetoresistive sensor () to keep either the frequency sum (fi+fc) of the first and second frequencies or the frequency difference (fi&#x2212;fc) of the first and second frequencies, and a processor for processing the filtered response signal and extract eddy current information on defects in the metallic object ().

Method and device for non destructive evaluation of defects in a metallic object

The device for measuring magnetic field by using a magnetoresistive sensor comprises at least one magnetoresistive sensor (), a module () for measuring the resistance of the magnetoresistive sensor (), a generator module () for generating an additional magnetic field in the space containing the magnetoresistive sensor (), and a control unit () firstly for selectively controlling the generator module () to apply an additional magnetic field pulse possessing a first value with first polarity that is positive or negative and magnitude that is sufficient to saturate the magnetoresistive sensor (), and secondly for selectively controlling measurement of the resistance of the magnetoresistive sensor () by the module () for measuring resistance.

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Rozay en Brie, France

Nicolas Biziere