The distribution of the impedance characteristic of a test object is detected by applying an alternate magnetic field of a low frequency to the test object and measuring the induced current generated therefrom.
The present invention relates to a magnetic impedance measurement device comprising an apply coil for generating an alternate magnetic field of variable frequency, a power source for the apply coil, at least one magnetic sensor means comprising a pair of magnetic sensors for detecting orthogonal vector components of a magnetic field generated from a test object, the vector components being parallel to the face of the apply coil, a measurement means for the magnetic sensor for measuring a detected signal from said magnetic sensor mean, the measurement means being located at a distance from the face of said apply coil and facing said test object, a lock-in amplifier circuit for detecting from an output of said measurement means a signal having the same frequency as the frequency of said apply coil and an analysis means for analyzing intensity and phase changes of an output of said magnetic sensor means with the use of an output signal of said lock-in amplifier circuit.