Which calibration step ensures the instrument's signal amplitude responds proportionally to a known reflector distance?

• A. Distance calibration
• B. Resolution
• C. Sensitivity calibration
• D. Verification of wedge angle

Answer: (C)

The main idea here is making sure the instrument’s amplitude readout scales properly with a known reference signal. Sensitivity calibration adjusts the gain so that an echo from a reflector at a known distance produces the expected display amplitude. This creates a predictable, proportional response of the signal amplitude to the reference signal, which is essential for interpreting flaw indications and comparing echoes from different depths.

Distance calibration, in contrast, is about making sure the time axis correctly maps travel time to depth, not about how loud or quiet the echoes appear. Verification of wedge angle relates to the geometry of the sound path, and resolution concerns the ability to distinguish two close reflectors rather than how amplitude scales with distance.