What type of reference blocks increase in diameter by 1/64-inch increments?

The type of reference blocks that increase in diameter by 1/64-inch increments is known as area-amplitude test blocks. These blocks are specifically designed for ultrasonic testing to provide a means of calibrating and standardizing measurements by offering a variety of known discontinuity sizes. The increments enable the precise assessment of a testing system’s sensitivity and performance across small variations in target size.

Area-amplitude test blocks are particularly beneficial in evaluating the response of the ultrasonic system to reflectors of varying sizes, thus allowing technicians to determine minimum sensitivity levels and validate equipment performance under controlled conditions. By understanding the differences in readings when testing these blocks, operators can ensure reliable results in real-world applications.

In contrast, other types of blocks mentioned, such as calibration blocks, step blocks, and flat-bottomed hole blocks, serve different purposes in ultrasonic testing. Calibration blocks are used for setting up and calibrating ultrasonic testing equipment without specific increment measurements. Step blocks provide different thicknesses rather than diameter increments, and flat-bottomed hole blocks are designed for identifying specific hole sizes instead of diameter variations.