inductance

Pressure magnetic effect

When the ferromagnetic material is subjected to mechanical force, mechanical stress is generated inside it, which causes a change in the magnetic permeability of the ferromagnetic material. This phenomenon is called a piezomagnetic effect. Specifically, it can be expressed as follows: when the material is subjected to pressure, the magnetic permeability coefficient decreases in the direction of the force, and the magnetic permeability increases in the vertical direction of the force; when the force is the tensile force, the effect is reversed; The magnetic permeability is restored. The piezomagnetic effect of ferromagnetic materials is also related to the magnetic field.

2. Working principle of pressure magnetic sensor

As shown in Fig. 3‐, four symmetrical small holes 1, 2, 3 and 4 are opened in the middle part of the piezoelectric material, and the excitation winding N12 is wound between the holes 1, 2, and the output is wound between the holes 3 and 4. Winding N34. When an alternating current is passed through the excitation winding, a magnetic field is generated in the core. If the space between the holes is divided into four regions A, B, C, and D, the magnetic permeability of the regions A, B, C, and D is the same when there is no external force. At this time, the combined magnetic field strength H is parallel to the plane of the output winding, and the magnetic lines of force are not interlinked with the output winding, and N34 does not generate an induced electromotive force, as shown in Fig. 3‐(b).

Under the action of pressure F, as shown in Figure 3‐(c), the A and B regions will be subjected to a certain stress, while the C and D regions are basically in a free state, so the magnetic permeability of the A and B regions decreases, and the magnetic resistance increases. In the large, the magnetic permeability of the C and D regions is basically unchanged. In this way, the magnetic lines of force generated by the excitation windings will be redistributed, and some of the magnetic lines of force will be closed around the C and D regions, so that the combined magnetic field H is no longer parallel to the N34 plane, and a part of the magnetic lines of force are interlinked with N34 to generate an induced electromotive force e. The larger the F value, the more magnetic flux is interlinked with N34, and the larger the value of e.