Defect Depth/Height Sizing using The 6dB or 20 dB Drop Technique

Using the #ACS_Group_Ultrasonic_Flaw_Detector in the #6dB_Drop or #20dB_Drop_Techniques: 1. After the defect length is sized, the next step is depth sizing by moving the probe to identify the position that produces the maximum reflected amplitude. Then using the controller on the ultrasonic flaw detector to adjust the gain so that the amplitude of this signal is at the 80% or 100% (±5%) FSH (Full-Screen Height). Note: In this case, it would be about 76% FSH. 2. The probe is moved close and away from the weld while noting the two points where the maximum reflected amplitude drops to 50% (-6dB) or 10% (-20dB) at the edges. The distance between the probe center at the each of those two points represents the depths and height of the flaw. Note: In this case, 76% FSH is dropped to about 38% FSH.