Direct magnetostriction and magnetoelastic wave amplitude lo measure a linear displacement

The change of the magnetization intensity induced by a tensile stress in magnetoelastic ribbons can be useful to evaluate a point displacement of an elastic body under deformation. The same measurement can be performed by means of the change in the amplitude of resonant magneteolastic waves, when a longitudinal stress is produced in the ribbons. A comparison between the two techniques is reported in this paper, with the aim to separate the sensitivity limits and the optimum method in different experimental conditions. It is shown how a large stress sensitivity of magnetization is related to a high stress sensitivity of the magnetoelastic waves amplitude but in a different range of applied stress. Generally, the first technique is most useful to investigate a large range of displacement(from 1 mu m up to 1 cm) with a good linearity but a decreasing precision if the displacement increases, while the second technique is the most sensitive and also precise (0.01 mu m) if little displacement ranges are to be investigated.