Reference standards containing a series of flat bottom holes of different diameters at the same depth in each block are called

• A. Wedge blocks
• B. Area amplitude blocks
• C. Notch blocks
• D. Step blocks

Answer: (B)

In ultrasonic testing, reference standards are used to calibrate how the instrument responds to reflectors and relate signal strength to reflector size. A block that contains a series of flat bottom holes all at the same depth but with different diameters shows how the echo amplitude increases as the reflector area grows. This type of reference is called an area amplitude block, and it provides a direct way to calibrate sensitivity and understand how amplitude relates to defect size. Wedge blocks are for angle and path calibration, notch blocks test detection of different flaw geometries, and step blocks calibrate depth response with stepped reflectors. So the area amplitude block is the correct description.