1.2.43
Search Unit
Device containing a piezoelectric material used for introducing vibrations
into a material to be inspected or for receiving the vibrations reflected
from the material. The active element of the search unit is defined as the
effective transmitting area. Search units are also called transducers or
probes. They may be single or dual and contain one or two piezoelectric
elements, respectively, for transmission and reception. The single search
unit is sometimes enclosed in a transducer wheel or search unit wheel. The
search unit may be manually handled and placed in direct contact with the
material to be inspected or may be held in a fixture for immersion
technique.
1.2.44
Sensitivity
Measure of the ultrasonic equipment's ability to detect discontinuities.
Quantitatively, it is the level of amplification of the receiver circuit in
the ultrasonic instrument necessary to produce the required indication on
the scope from the reference hole in the reference block. Also see
"standard reference level".
1.2.45
Shear Waves
Waves in which the particles within the material vibrate perpendicularly to
the direction in which the wave travels or propagates. Also called
1.2.46
Shear Wave Inspection
Inspection technique using shear waves in a material. The search unit is
placed at an angle to the contact surface of the material so the resultant
refracted sound is a shear wave at an angle to the normal.
1.2.47
Standard Reference Level
Mid-screen height reflection when beaming at the 1.52 mm 0.060 inch hole in
the primary reference block or the reference hole in the secondary standard.
1.2.48
Surface Waves
Waves that propagate along the surface of the material and penetrate it to
only about 1/2 wavelength. Also known as Rayleigh waves.
1.2.49
Test Frequency
Operating frequency in hertz per second of the search unit during period of
activation. Frequency is usually expressed in megacycles per second or
megahertz. The latter term has been adopted for international use and is
preferred.
1.2.50
Video Form
Type of signal presentation on a CRT in which only the upper or position
half of the signal appears.
1.3
GENERAL REQUIREMENTS
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NOTE: The designer will indicate the extent of
SECTION 05092A
Page 10
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