Nominally identical ceramic-element ultrasonic transducers have been used successfully to calibrate ASTM E127-type flat-bottom-hole (FBH) aluminum reference blocks. The transducers all had nominal center frequencies of 5 MHz, and nominal element diameters of 9.5 mm (0.38 in) or 10.7 mm (0.42 in). The inherent performance variability among these transducers was eliminated by monitoring and matching the frequency content of the generated ultrasonic pressure pulses. The pulses were monitored with a polymer polyvinylidene (PVDF) membrane hydrophone and the frequency content was matched by adjusting the shape of the excitation waveform. Several different common excitation shapes were examined in detail. Results indicate that this type of tuning procedure will result in similar performance among nominally identical ceramic-element transducers. This may ultimately allow for the routine reliable calibration of long metal-path blocks that cannot be calibrated using quartz-element ultrasonic transducers as currently stipulated in E127.
Citation: Materials Evaluation
Pub Type: Journals
ASTM E127, ceramic transducers, FBH, membrane hydrophone, PVDF, reference blocks, ultrasound