Phased array transducers are functionally categorized according to the following basic parameters:
Type: Most phased array transducers are angle beam type, designed for use with either a plastic wedge or a straight plastic shoe (zero degree wedge) or delay line. Direct contact and immersion transducers are also available.
Frequency: Most ultrasonic flaw detection is done between 2 MHz and 10 MHz, so most phased array transducers fall within that range. Lower and higher frequency probes are also available. As with conventional transducers, penetration increases with lower frequency, while resolution and focal sharpness increase with higher frequency.
Number of elements: Phased array transducers most commonly have from 16 to 128 elements, with some having as many as 256. A larger number of elements increases focusing and steering capability, and can increase area coverage as well, but also increases both probe and instrumentation costs. Each of these elements is individually pulsed to create the wavefront of interest. Hence the dimension across these elements is often referred to as the active or steering direction.
Size of elements: As element width gets smaller, beam steering capability increases, but large area coverage will require more elements at higher cost.
The dimensional parameters of a phased array are customarily defined as follows:
This information is use by instrument software to generate the desired beam shape. If it is not entered automatically by probe recognition software, then it must be entered by the user during setup.