| 摘要 |
<p>PURPOSE:To reduce greatly the error of detection due to the reflected wave for a position detecting device using a magnetic distortion delay line, by providing two detection coils and at the same time setting the distance between the two coils at (1/2 X pulse duration X speed of propagation). CONSTITUTION:Two detection coils 31 and 32 are distributed with a distance of length l, and the distance from the coil 32 to a flaw 7 is referred to as L. In this case, l is selected to 1/2X(driving pulse duration)X(speed of propagation of magnetic distortion vibration), and accordingly a phase difference of 90 deg. is obtained between the signals detected by the coils 31 and 32. The time points Tr1 and Tr2 when the signals are obtained from the coils 31 and 32 with vibration i and reflected wave r have a shift of FDELTAT the time point of detection in case no reflected wave exists. When the point q of detection of a magnetic distortion line 1 is set at the center between the coils 31 and 32, an accurate value of detection can be obtained with no error caused by the reflection at the time point of detection and at the point q.</p> |
