Eddy‐Current Testing with GMR Magnetic Sensor Arrays

The advent of GMR magnetic sensors and GMR sensor arrays with frequency‐independent sensitivity offers improvements in speed, depth, and resolution in eddy‐current testing. Arrays of GMR magnetic sensors allow rapid scanning of an area for defects in a single pass. The small size and low power consumption of these solid‐state magnetic sensors enable the fabrication of compact arrays of sensors on circuit boards and even on‐chip sensor arrays. Arrays have been fabricated with sensor spacing as small as 5 micrometers when fine resolution is required. GMR sensor elements can be deposited on active silicon substrates facilitating on‐chip signal processing and multiplexing. This integration simplifies the sensor/signal‐processing interface, minimizes the number of leads, and can reduce the effect of noise. This paper will discuss the technology of fabricating arrays on GMR sensors, especially on‐chip arrays. Integrated sensor arrays with on‐chip signal processing and multiplexing will be described. Finally, so...