Detection of small gas bubble using ultrasonic transmission-mode tomography system

This paper presents the development of an ultrasonic transmission-mode tomography system for the detection of small gas bubble using higher frequency ultrasonic sensors. The selection of the sensors is important and must be suitable to the application design. Consideration on the natural limitation of ultrasonic wave is also noted as the higher the frequency of the ultrasonic transducer, the better the sensitivity but lower penetration depth. 16-pairs of these ultrasonic sensors are installed and fixed inside a sensor jig which is designed to hold all the sensors. The sensor jig is also mounted on the circumference of a vertical column which will be used as the investigated process vessel. The developments presented also include the non-invasive fabrication techniques, the electronic measurement circuits, image reconstruction technique, and finally on the imaging results of the proposed system.