Device and method for magnetically sensing current in plate structure

A device comprising:

• a magnetic head for sensing changes in current-induced magnetic flux as the head is positioned over a structure and for providing a head output signal indicative of any sensed changes in magnetic flux, the changes in magnetic flux including any relative changes that arise due to movement of the head relative to the structure;
• signal processing circuitry for processing the head output signal to produce a data signal indicative of how much, if any, current flows in plate structure below the head;
• and
• signal processing circuitry for processing the head output signal to produce a data signal indicative of how much, if any, current flows in the structure below the head;
• and
• a location sensor for determining where the head is positioned relative to the structure, the location sensor comprising a light source and a light sensor for generating an electrical signal in response to light reflected off the structure after being emitted by the light source.