| 摘要 |
PURPOSE:To obtain a means which can accurately measure the thickness of a material to be examined by eliminating the confusion of waves reflected from the front end of an ultrasonic probe and from the surface of the material to be examined and accurately reading pulses respectively generated from reflected waves from the upper and lower surfaces of the material. CONSTITUTION:An ultrasonic probe 3 is installed in such a state that its front end is separated from the surface of a material to be examined by a first set distance L1 corresponding to >=1/2 of the wavelength of used ultrasonic waves. Then reading of reflected pulses is started when the ultrasonic waves reach a position separated from the front end of the contact 3 by a second set distance L2 which is shorter than the first set distance L1. |
