2. Description of the test bench

A typical measurement bench consists of an electrical pulse generator, an oscilloscope for visualization and/or an acquisition card for transferring ultrasonic signals to a computer for signal processing. It is of course essential to use a sampling frequency at least equal to twice the signal frequency to meet Shannon's criterion. One or two ultrasonic probes are connected to the electrical generator, depending on the chosen working mode: reflection or transmission (figure 6 ). This description can be supplemented by displacement plates, attitude adjustment systems, etc.