Modifications to Standard Pulse Techniques for Ultrasonic Velocity Measurements

A description is given of modifications to the “sing-around” and coincidence techniques for velocity measurement. In the case of the “sing-around” method a gate is incorporated which effectively lengthens the ultrasonic path by allowing retriggering on multiply reflected pulses. This allows the use of short solid specimens having low attenuation. The coincidence technique is modified by using an unrectified rf display and an electronic counter-timer to measure the pulse recurrence frequency. In both methods, an accuracy of 1 in 104 can be achieved in measuring the transit time for 10-Mc/sec waves through a low-absorbing specimen before correction is made for the effect of transducer-specimen bonds, etc.