What feature distinguishes pulse-echo testing from through-transmission testing?

The feature that distinguishes pulse-echo testing from through-transmission testing is the measurement of reflection from a single surface. In pulse-echo testing, a single transducer emits ultrasonic waves that travel through the material, reflect off any discontinuities (such as flaws or boundaries), and then return to the same transducer. This capability allows for the detection of internal defects and the assessment of material thickness without the need for a second transducer.

In contrast, through-transmission testing involves two separate transducers, with one acting as the transmitter and the other as the receiver. This technique requires the ultrasonic waves to travel completely through the material, which means that it is primarily sensitive to the overall condition of the material rather than the reflection from internal features.

Understanding this fundamental distinction helps in selecting the appropriate testing method based on the specific requirements of the inspection, such as the types of defects being investigated or the geometry of the material being tested.