| 摘要 |
An apparatus for detecting defects in a rotating metal surface such as a mill roll 12 comprises a test head 10 including an eddy coil which is movable relative to the surface along scan paths. An oscillating signal induced at the eddy coil is received and recorded as the coil is moved along each path. A representation of the received oscillating signal in relation to each scan path is outputted on a display 16. The received signal is displayed as raw data (Figure 2a) which is not demodulated so that circumferential defects can be seen as changes in wave frequency. Demodulated data indicates longitudinal defects (Figure 2b). Defect location is facilitated by a further function of the apparatus, by which user input to an interface causes a light source 14 to illuminate a selected part of the metallic surface. |
