Re: Area Amplitude Blocks ----------- Start Original Message ----------- : When do you use these blocks. I understand the purpose of the DAC blocks but dont know when I would use the AA blocks? ------------ End Original Message ------------
Area amplitude blocks have been misused to determine linearity of response to be expected for ultrasonic inspection of various materials. There are many problems with this application including the shape, surface condition, grain structure and general attenuation of the material as well as the frequency, size and damping of the transducer. These factors are discussed in some detail in my paper "Ultrasonic Area-Amplitude Linearity Limitations" in the August 1992 issue of ASNT's "Materials Evaluation".
They have sometimes been used, per ASTM E 317, Method A, to determine instrument linearity. Limitations of this use are also covered in the referenced paper which indicates that Method B, using a calibrated attenuator, is preferable.
The blocks may be properly used, with a given transducer to compare sensitivity and noise levels of various ultrasonic flaw detection instruments or to check the performance of a given instrument with time.