Investigation into slow scan front-end control of a transmission mode ultrasonic system

Abstract

In this paper, we present simulative and experimental studies into ultrasonic sensors to investigate a known problem of slow scanning in a transmission mode ultrasonic system. First, a sensory design for a general transmission mode system was discussed in terms of sensor types and sensing approach. A contemporary comparison was performed to two recent ultrasonic applications to understand the real time constraint. It was found that the long repetition delay between two separate excitations and the multiple pulses of the transmit carrier led to the slow system. An acoustic-based simulation was conducted using the finite-element modeling method to perform time domain analysis in a liquid column of a stainless-steel pipe. Simulations showed that a single ultrasonic pulse was sufficient to penetrate the measuring column, and an increase in emission frequency will decrease both acoustic pressure and reverberation effect. Among the investigated frequency range, 5-MHz emission frequency was the optimum one, to have sufficient energy and shortest reverberation, to use in the investigated column. Next, the sensing instrumentations were discussed. Experiments in measuring full or empty of liquid inside a column of the stainless-steel pipe were conducted. Ultrasonic pressures and reverberation effects were observed and measured. In conclusion, a good corroboration is achieved between the simulative and experimental results that a shorter repetition delay can be achieved with the emission strategy of a single edge trigger and a high frequency of 5 MHz.