What does an A-scan display plot?

An A-scan display in ultrasonic testing (UT) specifically plots signal amplitude versus time. This type of display allows technicians to visualize the strength (or amplitude) of the reflection received from an ultrasonic pulse over time, which corresponds to the depth of various features within the material being tested.

In an A-scan, the horizontal axis typically represents time, which correlates to the distance the ultrasonic waves travel in the material. The vertical axis shows the amplitude of the received signals, which indicates the intensity of the reflections. This can help identify flaws or changes in material properties based on how strong the echoes are at various time intervals. When fluctuations in amplitude occur, they are often indicative of imperfections such as cracks, voids, or inclusions.

The other options do not accurately describe the nature of an A-scan display. For instance, plotting signal phase versus frequency relates more to frequency domain analysis, while signal energy versus distance would not capture the time-based aspect of distance estimation in UT. Signal quality versus depth focuses on different metrics that are not represented in a standard A-scan. Therefore, understanding that an A-scan is fundamentally about the relationship between signal amplitude and time helps clarify its essential role in ultrasonic testing.