2.3. Modelling on Number of Sensor and Its Arrangement
The sensor configuration is the important factor in the efficiency of data acquisition [14]. In designing the sensor
configuration for flaw detection around the pipe surface, the distance from the ultrasonic sensing ring to the pipe
must be within the sensing range (40-60 mm) where the ultrasonic energy can be sensed and detected. Therefore,
each sensor (transceiver) is arranged closely side by side with distance of 50 mm to the pipe surface. A distance of
50 mm is well-suited as it may produce a small area of the ultrasonic signal. The number of transceiver sensors and
its arrangement are determined according to the area of ultrasonic signal detected on the pipe surface. Based on the
testing conducted, the area of ultrasonic signal covered by a transceiver sensor is approximately 20 mm. The
ultrasonic transceiver sensor is arranged accordingly to the area verified with an acceptable distance or gaps between
sensors (side by side) to avoid overlapping signals from each sensor, as shown in Fig. 4. The selection of distance
from the sensor to the pipe surface and the arrangement of the sensors are significant to optimise the number of
sensors within the sensing ring. The number of sensor used will determine the number of pixel and therefore
produce a good resolution for the image reconstruction.