Olympus EPOCH 1000 Series, User Manual

Page: 336 / 364

910-269-EN, Rev. B, June 2011
324 Appendix B
Attenuation The loss in acoustic energy that occurs between any two
points of travel. This loss may be due to absorption,
reflection, scattering, and other phenomena.
Back or back-wall
echo The echo received from the side of the specimen opposite
the side to which the transducer is coupled. This echo
represents the thickness of the specimen at that point.
Background noise Extraneous signals caused by sources within the ultrasonic
testing system and the material being tested.
Beam-index point
(BIP) For an angle beam probe, the point where the sound
leaves the wedge and enters the specimen.
Cal. block velocity Material sound velocity for the calibration block.
Couplant A material (usually a liquid or gel) used between the
transducer and the test specimen to eliminate air from this
space and thus facilitate the passage of sound waves into
and out of the specimen.
Critical defect Either the largest tolerable defect or the smallest
intolerable defect. The critical defect size is usually given
by a specification or code.
Cross talk An unwanted condition affecting dual element
transducers in which acoustic energy travels from the
transmitting crystal to the receiving crystal by routes other
than the intended path through the material.
Damping (control) A variable resistance across the pulser circuit output
which shapes the excitation pulse. Typically it is used to
change pulse characteristics to optimize either penetration
(low damping) or near-surface resolution (high damping).
Damping material Any gel, rubber-like substance, or other material which,
when used in the transducer, results in a shorter ringing
time of the piezoelectric crystal.
Table 37 Glossary (continued)
Term Definition
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