910-269-EN, Rev. B, June 2011
326 Appendix B
Gain Used in electronics with reference to an increase in signal
power; usually expressed as the ratio of the output power
to the input power in decibels.
Gate An electronic baseline display used to electronically
monitor portions of the displayed range with reference to
distance or amplitude.
Hertz (Hz) The derived unit of frequency defined as the frequency of
a periodic phenomenon of which the period is one second;
equal to one cycle per second.
Symbol Hz. 1 kilohertz (kHz) = 10
3
cycles per second
1 Megahertz (MHz) = 10
6
cycles per second.
Immersion testing A test method, useful for testing irregularly shaped parts,
in which the part to be tested is immersed in water (or
other liquid) so that the liquid acts as a couplant. The
transducer is also immersed in the liquid, but not in
contact with the part being tested.
Incidence, angle of The angle between a sound beam striking an acoustic
interface and the normal (that is, perpendicular) to the
surface at that point. Usually designated by the Greek
symbol α (alpha).
Indication The signal displayed on the data display signifying the
presence of a sound wave reflector in the part being tested.
Indication (defect)
level
The number of decibels of calibrated gain which must be
set on the instrument to bring the indication (defect) echo
signal to peak at the reference line on the screen.
Initial pulse (IP) The pulse of electrical energy sent by the pulser to the
transducer.
Leg In angle beam testing, the path the shear wave travels in a
straight line before being reflected by the opposite surface
of the material being tested.
Table 37 Glossary (continued)
Term Definition
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