What does it mean when a vertical indication reaches the maximum signal height that can be displayed on an ultrasonic instrument?

When a vertical indication reaches the maximum signal height that can be displayed on an ultrasonic instrument, this phenomenon is referred to as signal saturation. This indicates that the amplitude of the ultrasound reflection from a specific discontinuity or flaw is so strong that it has exceeded the upper limit of the instrument's display capability. In this situation, the measurement may no longer be proportional to the actual signal strength, leading to a loss of information about the nature of the discontinuity.

Signal saturation can often occur with large or very reflective flaws, where the intensity of the returning signal overwhelms the instrument's ability to accurately measure it. As a result, the display will show the peak amplitude at the maximum limit, and it may appear as a flat line on the instrument, obscuring finer details of the signal.

Signal saturation is critical to recognize because it may lead an operator to misinterpret the findings if they fail to understand the limits of the equipment's measurement capability. This knowledge is particularly crucial for ensuring accurate assessments in various applications of ultrasonic testing.