The ideal arrangement of sensors based on area of ultrasonic signal has produced twenty eight (28) of transceiver
sensors with a diameter of 18 mm within the ultrasonic sensing ring as shown in Fig. 4. As the diameter of pipe used
in the system is 219.1 mm and the distance from the sensor to the pipe surface detected is 50 mm, the diameter of
the ultrasonic sensing ring is 319.1 mm (219.1 mm + 100 mm). The uncovered area assemble between two
ultrasonic signals on the pipe surface is about 3 mm. Meanwhile, the void area on the pipe surface due to the size of
ring’s holder (54 mm) is about 39.5 mm. From the sensor arrangement, the distance between sensors is about 14.1
mm. Based on the distance from the sensor to the pipe surface, and the area of ultrasonic signal, the calculated beam
angle is about 22.4º.