Abstract
In this instrument the conductor being inspected is passed axially through a coil forming a part of the tuned circuit of an oscillator. Any flaws in the conductor cause a change in the tuning, and thus in the frequency generated, which is conveniently observed through heterodyning with a fixed frequency. By using high frequency, of the order of 6000 kilocycles, the response is limited to flaws near the surface of the conductor. This instrument is used in the factory inspection of tungsten wire, particularly for the location of longitudinal cracks, and is also effective in the determination of asymmetry of coated wires.

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