| 摘要 |
An apparatus for measuring material properties of an object of ferromagnetic material comprises a probe (10, 40), the probe comprising an electromagnet core (18, 42) defining two spaced-apart poles (20, 44) for inducing a magnetic field in the object (12), and a drive coil (22, 46) wound around the electromagnet core, and means to supply an alternating electric current to the drive coil to generate an alternating magnetic field in the electromagnet core and consequently in the object. The probe also includes two sensing coils (30, 50) arranged in the vicinity of each of the poles, for sensing the magnetic flux density that links the core and the object. Such sensing coils (30, 50) are significantly more sensitive to changes in material properties than are sensing coils overwound onto the drive coil. |
