Long GMI sensors for the detection of repetitive deformation of a surface

Results on development and testing of a long giant magneto-impedance sensor for deformation detection is reported. The effect of the external magnetic field and tensile forces on the sensitivity to bending has been studied with the aim to optimize and tune the sensor response as needed for various applications. A novel device was designed to create a deformation easy to define, measure and reproduce as a curved surface with adjustable curvature radius. The dependence of the sensor output voltage on the inverse of the bending radius in different conditions was analyzed and explained by taking into account the magnetic properties and magnetic domain structure of the Co68.18Fe4.32Si12.5B15 amorphous magnetic wire which was used as the sensitive element. The obtained results show that long giant magneto-impedance sensors can be reliably used in order to detect the curvature of a large surface and can even operate independent of the presence of low external magnetic fields.