910-269-EN, Rev. B, June 2011
Glossary 329
Resolution The ability of the test system (instrument and transducer)
to distinguish reflectors at slightly different depths.
Scanning level The number of decibels of calibrated gain above the
reference level added to ensure seeing potentially
significant reflectors at the end of the V-path in a weld
inspection.
Second critical angle The minimum incident angle in the first medium at which
the refracted shear wave leaves the body of the test
specimen.
Sensitivity The ability of the test system (instrument and transducer)
to detect a given size reflector at a given distance.
Signal-to-noise ratio The ratio of amplitudes from the smallest defect
considered significant and those caused by random
factors, such as grain scattering or instrument noise.
Single element probe A probe containing only one piezoelectric element, which
is used to both transmit and receive sound.
Skip-distance In angle beam testing, the surface distance which
represents one V-path of sound in the material.
Sound beam The characteristic shape of the ultrasonic wave sent into
the material.
Sound path distance The distance from the transducer beam index point to the
reflector located in the specimen, measured along the
actual path that the sound travels. Sometimes referred to
as angular distance in angle beam testing.
Straight beam probe
(Normal beam probe)
A probe which transmits the sound into the material
perpendicular to the entry surface.
Surface wave Mode of wave propagation characterized by an elliptical
movement of the particles (molecules) on the surface of
the specimen as the wave front moves forward, this
movement penetrating the specimen to a depth of one
wavelength.
Table 37 Glossary (continued)
Term Definition
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