What is a DAC curve used for in UT thickness measurements?

• A. A DAC curve is a distance-amplitude correction curve used to relate echo amplitude to reflector distance and calibrate sensitivity across depths.
• B. A DAC curve is a dynamic area calibration for screen brightness.
• C. A DAC curve maps transducer frequency to material category.
• D. A DAC curve defines the maximum depth to measure.

Answer: (A)