ACCURATE MEASURING METHOD OF RECIPROCATING TIME OF ULTRASONIC WAVE UTILIZING PULSE REFLECTION METHOD

摘要

PURPOSE:To measure the reciprocating time of a ultrasonic wave with high accuracy by providing a thin plate between a vibrating and detecting element and the surface of an object to be measured, said thin plate being made of a material having a smaller acoustic impedance than said object to be measured and a thickness 1-4 times the wavelength of said ultrasonic wave. CONSTITUTION:A ultrasonic pulse is projected from a vibrating element 4 in contact with the surface of an object to be measured. A ultrasonic wave reflected at the reverse surface of the object 2 to be measured is converted to an electric signal by the detecting element 4. Thus, the time for the ultrasonic wave to be propagated in the object 2 is measured. A delay stabilizer 13 is intervened in tight contact between the vibrating and detecting element 4 and the object 2 to be measured. The stabilizer 13 is made of a material having a smaller acoustic impedance that the object 2 to be measured and a thickness 1-4 times the wavelength of the ultrasonic wave. The time interval between a first reflecting wave 6 when the incident ultrasonic wave reflected once at a rear surface 5 of the object 2 returns to a front surface 3 and a second reflecting wave 7 when the first reflecting wave 6 is reflected at the front surface 3 and further at the rear surface 5 to return to the front surface 3. The reciprocating time of the ultrasonic wave can be thus measured with high accuracy.