Modular Eddy Current Micro Sensor

In order to provide a contactless measurement technique to examine products during the fabrication process, a modular design of an eddy current micro sensor was developed and fabricated in thin-film technology. The sensor consists of two parts, a single-turn excitation coil and an anisotropic magneto-resistance (AMR) sensor. The AMR sensor detects the change of the magnetic field induced in a sample by the excitation coil. Initial investigations were conducted to prove the capability of the completed eddy current micro sensor. A defect was created on the surface of a Cu probe. The electrical output signal of the AMR sensor was subsequently compared to optical measurements of the surface profile of the crack. There is a high correlation between the optical measurements and to those of the eddy current micro sensor.