Abstract
Magnetic nondestructive testing is very useful for detecting a crack on the surface or near the surface of ferromagnetic materials. Also, the distribution of the magnetic flux leakage (DMFL) on the surface has to be obtained quantitatively to evaluate the crack. And the DMFL measurement on the high lift-off can be used for the protection of magnetic sensors from damages due to weak environment such as high temperature, vibration, vapor, and dust. Because the magnetic field is inversely proportional to the square of the lift-off, improved techniques for increasing the detection probability are strongly demanded. The magnetic camera using magnetic lens is proposed to satisfy these demands such as obtaining DMFL, measuring on the high lift-off, and improving sensitivity of sensor. This paper proposes several techniques for improving the detection probability of the magnetic camera. The surface mounted device type operational amplifiers, AD620 and LM324, were compared with respect to sensitivity, S/N ratio, delay time, and Fast Fourier Transform analysis. Also the reference single ended and the non-reference single ended connections were compared.
