What is a potential consequence if velocity calibration is incorrect during UT?

• A. Depth and thickness measurements will be inaccurate.
• B. The transducer will overheat.
• C. The display will automatically correct.
• D. The instrument will beep and shut down.

Answer: (A)

In ultrasonic testing, the depth you read from an echo comes from the travel time of the sound pulse and the material’s acoustic velocity. The conversion time × speed, divided by two for the round trip, gives the distance to the reflector. If the velocity value used in the instrument is incorrect, every depth measurement is biased because you’re mapping time to distance with the wrong speed. That means the reported thickness of the part or the position of a flaw in depth will be off, sometimes by a large amount, even if the echoes themselves are clear. To prevent this, velocity calibration is done with a reference block of known thickness and material, and temperature effects are considered since sound speed changes with temperature. The other outcomes—transducer overheating, automatic display correction, or an audible shutdown—do not arise from incorrect velocity calibration; they reflect power, software behavior, or hardware faults rather than the depth conversion being miscalibrated.