Evaluation of An Eddy-Current Tape-Head Probe

The objective of this task is to evaluate and characterize a new type of eddy-current probe that is based on ferrite tape-head technology. Preliminary tests were conducted last year at 100 kHz using modified, commercially available floppy-disk tape heads and subassemblies. Some customized probes also were constructed for SRI by a tape-head manufacturer. These customized probes were made of ferrite material available at the manufacturer’s facility; however, this material subsequently was found to be too lossy for the eddy-current application. Nevertheless, test results obtained using the floppy-disk tape-head probes proved to be very promising from the standpoint of sensitivity, lift-off discrimination, and the ability of this type of probe to detect cracks inside and at the edges of holes