The energy of the ultrasonic pulse is transmitted in form of a cone along the transducer axis. The highest intensity is on the axis and decreases with rising angles. The angle of beam is defined by the angle
through which the energy of the ultrasonic pulse is reduced of 33% of its maximum value.
The best detection is given by an object that stands vertical to the transducer axis. To give a save detection, the object should not have an greater angle than half of the angle of beam ( /2). (Fig. 2) If the object is canted at a greater angle, there is no reflection of the ultrasonic pulses. An object with a flat surface and canted at an angle of 45° to the transducer axis refracts the ultrasonic pulse in an angle of 90°. An ultrasonic pulse can be compared to a light beam.