| 摘要 |
An apparatus, using three gradiometers, measures the spatial variation of a magnetic field along a path of motion of the apparatus. The apparatus comprises three gradiometers oriented along the mutually orthogonal axes, x', y' and z' defined on the moving platform. The outputs of the gradiometers are the gradients of the magnetic field when the motion is considered to be in the y' direction. Three filters, each having an input connected to the output of one of the gradiometers, are constructed to have an output signal which has a relatively narrow positive peak with a relatively wide negative area on each side of the peak. The net area is approximately zero when the input to the filter is a doublet. Three squares, each having an input connected to the output of a filter, square their input signals. A summer, having three inputs connected to the outputs of the squarers, obtains the sum of the squares of the high-pass filtered components x', y' and z' of the magnetic field. A circuit, whose input is connected to the output of the summer, takes the square root of its input signal and outputs a signal corresponding to the magnitude of the variation of magnetic field along the path of motion of the platform.
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