a magnetoelastic sensor . the magnetoelastic sensor uses strain - induced magnetic anisotropy to measure the tension or compression present in a plate . during construction , an annular region of the plate is magnetized with a circumferential magnetization . magnetic field sensors are placed near this magnetized band at locations where the magnetization direction is non - parallel and non - perpendicular to the axis of tension . the strain - induced magnetic anisotropy caused by tension or compression then produces a shift in the magnetization direction in the plate regions near the field sensors , thereby causing magnetic field changes which are detected by the magnetic field sensors . the magnetic field sensors are connected to an electronic circuit which outputs a voltage signal which indicates the tension or compression in the plate .