Run time measurement of acoustic pulses in magnetoelastic screws, involves detecting change in the measuring field by inducing voltage pulse in the surface region of the screw

摘要

The magnetic measuring field of a measuring head (1) is cut off in the surface region (7) of a screw (3). A pulse generator (10) then generates the initial magnetic pulse in at least one of the coils (S1-S3) linked with workpiece. Based on the resulting magnetoelastic effect on the surface region, an acoustic pulse is reflected at the opposite end of the workpiece. A detector (11) then detects the change in the measurement field caused by the reflected acoustic pulse by inducing a voltage pulse in the surface region of the screw. As a result, the period by which the first and second magnetic pulses are generated will correspond to the run time of the acoustic pulse in the screw. An independent claim is also included for a device in measuring the acoustic pulses on the surface of a magnetoelastic screw