| 摘要 |
<p>PURPOSE:To enable a small amount of a magnetic body to be detected by providing a pair of magnetic field forming coils which are separated by a constant distance and placed in parallel so that a uniform magnetic field is formed around a sensor of a Helmholtz coil which detects a change in the amount of flux and a device which measured the electromotive force which is induced due to change in the amount of flux. CONSTITUTION:Magnetic field forming coils 5 and 6 are wound between side plates 2a and 2b and 4a and 5b, respectively. Sub magnetic field coils 11 and 12 are placed on inner surfaces of frames 2, 3, and 4. The sub magnetic field coils 11 and 12 are placed so that they cross the magnetic field coils 5 and 6. The coils 5 and 6 which form a magnetic field and coils 11 and 12 are operated, thus enabling a combined magnetic field with a uniform strength to be formed within a space 10. Sensor coils 20a, 21a, and 22a and 20b, 21b, and 22b are placed on inner surfaces 7 and 8, respectively. When a magnetic body passes through the space 10, the flux is disturbed, the amount of flux is changed, and an electromotive force is generated at both edges of the coil. A sensor distinguishes the change of the magnetic field from an influence of an external magnetic field clearly even if the magnetic body is small.</p> |
