Abstract: The invention relates to a magnetic sensor device (10) comprising magnetic field generators (11, 13) for generating a magnetic excitation field (B) in an investigation region and a magnetic sensor element (12) for measuring magnetic reactions fields (B?) generated by magnetized particles (2) that are bound to binding sites (3) in the investigation region. Both the magnetic field generators (11, 13) and the magnetic sensor element (12) are driven with electrical power, wherein the ratio of the power that is dissipated in said components is kept in a predetermined interval. The magnetic field generators may preferably be realized by excitation wires (11, 13) and the sensor element (12) by a magneto-resistive element, for example a GMR element. In this case, it is preferred that about equal amounts of power are dissipated in the excitation wires (11, 13) and the GMR element (12).