The present invention is for a simple, reliable and inexpensive method to calibrate a defect signal to determine the size of a defect in a pipe. A first reflected signal is received from the test area of the pipe. After attaching a clamp, a second reflected signal is received from the test area of the pipe. If defects are in the test area, by appropriate calculations using the first reflected signal and the second reflected signal, the size of the defect can be determined.
Hegeon Kwun; Sang-Young Kim; Glenn M. Light