910-269-EN, Rev. B, June 2011
Glossary 327
Linearity, vertical or
amplitude
The characteristics of an ultrasonic test system indicating
its ability to respond in a proportional manner to a range
of echo amplitudes produced by specified reflectors.
Linearity, horizontal
or distance
The characteristics of an ultrasonic test system indicating
its ability to respond in a proportional manner to the time
at which echo signals produced by specified reflectors
appear.
LOS Acronym for loss of signal.
Longitudinal wave Mode of wave propagation characterized by particle
movement parallel to the direction of wave travel.
Main bang Term used to describe the initial pulse voltage.
Mode conversion Changing a portion of sound beam energy into a wave of a
different mode due to refraction at incident angles other
than zero degrees. In NDT, this usually involves
conversion of longitudinal waves into shear waves or
surface waves.
Peaking up Maximizing the height of any indication displayed on the
data display by positioning the main axis of the sound
beam directly over the reflector.
Penetration The ability of the test system to overcome loss in acoustic
energy due to the material; that is, the ability of the sound
beam to by-pass small reflectors such as grain boundaries
and porosity in the specimen.
Piezoelectric
elements
A family of materials (such as lead metaniobate, quartz,
lithium sulfate) that possess the characteristic ability to
produce:
a) A voltage differential across their faces when deformed
by an externally applied mechanical force, and
b) A change in their own physical configuration
(dimensions) when an external voltage is applied to them.
Probe Another name for transducer.
Table 37 Glossary (continued)
Term Definition
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