Inspection Systems Basics

The simplest UT inspection configuration is called a “pulse/echo inspection”.  There a single ultrasonic transducer serves as both a generator and receiver of sound.  The transducer emits a short-duration pulse of sound and then “listens” for returning echoes.  If a defect is present in the object being inspected, a sonic echo from that defect signals its presence.   Another inspection type, termed “pitch/catch”, uses one transducer to generate sound and a second transducer to detect sound.  A common type of pitch/catch inspection (termed “through transmission”) is used to inspect flat panels, say of composite material.  There the transmitting transducer is on one side of the panel and the receiver is on the other side.  A problem in the panel, such as a delamination between layers, will often result in a diminution of the received sound.

UT inspection systems differ in their details, but all contain the basic elements pictured below.  A device called a pulse/receiver sends a voltage pulse to the transducer where it is converted into a sound pulse which travels into the component under inspection.  Returning sound echoes are converted back into electrical signals by the transducer and passed back to the pulser/receiver for amplification.  The amplified signals are then typically sent to a digitizing oscilloscope for display and to a computer for analysis and storage.