Eddy current materials testing - using multiple frequencies and multiplexers controlled by timing pulse generator

摘要

In a non-destructive test of materials by the eddy current method, several frequencies in the range 100-400kHz are applied to a test coil to produce a primary magnetic field. This generates eddy currents in the workpiece with an associated secondary field. A measuring coil determines the in-phase and reactive components of the impedance. A timing pulse generator feeds the test frequencies fast enough in the coil to blur the frequencies of each cycle no more than is required for the local resolving power. This reduces the amt. of electronic instrumentation required and provides a local allocation of the signals of adequate accuracy.