| 摘要 |
A fiber optic magnetic field gradiometer uses the first derivative of a magnetic field associated with a corrosion process to determine the location on the surface of a metal of the corrosion at its onset or very early stages, whereas eddy current type detectors detect the corrosion only after a significant amount of the metal has already been removed. Two adjacent flat magnetic transducers made of magneto-strictive glass, onto which are secured two optical fibers, are immersed in an applied magnetic field to null out material differences in the earth's magnetic field. The optical fibers are secured to a surface of each transducer to provide a relatively flat sandwiched pair of transducers. The flat magnetic transducers are sandwiched together and scanned over the metal surface. A magnetic field associated with the corrosion process in the direction of the axis of the flat magnetic transducers causes an optical path length change in the fibers. The overall path length's change is proportional to the first derivative of the magnetic field.
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