| 摘要 |
For detecting flaws in the threaded end (26) of a ferromagnetic pipe (21), a magnetic force is applied to produce a field generally axially through the threaded pipe end, first and second means (55, 56) adjacent successive crests (28, 29) of a thread sense generally radial magnetic field and generate a first and second signal (51, 52) corresponding to the sensed magnetic fields, and means (42) differentially connect the signals generated by said first and second sensing means. In this way, a differential output signal is produced in response to a flaw between the crests of the thread being inspected. Means (60) can also be provided for helically rotating the sensing means (55, 56) to follow a path corresponding to the threads of the pipe, whereby the first and second signals vary with time. |
