vertical height of the indication measured from peak-to-peak for radio
frequency indications and trace-to-peak for video indications.
1.2.4
Attenuation
Dissipation or loss of energy as ultrasonic vibrations travel through the
material. Attenuation is caused almost entirely by scattering of the
ultrasonic vibrations generated by the search unit.
1.2.5
Attenuation-Correction Controls
Circuitry to provide a continuous increased amplification with respect to
time. This circuitry compensates for the reduction in sensitivity with
depth as a result of sound beam divergence and its attenuation in material.
1.2.6
Back Reflection or End Reflection
Reflection from the opposite side, end, or boundary of the material into
which the ultrasonic energy was introduced.
1.2.7
Calibrated Gain Control (Attenuator)
Circuitry with which gain can be increased or reduced finite amounts by
switching electrical signal attenuation into the circuit.
1.2.8
Process of comparing an instrument or device with a standard to determine
accuracy or produce a scale.
1.2.9
Cathode Ray Tube (CRT)
Electron tube in which a controlled beam of electrons from the cathode is
used to produce an image on a fluorescent screen at the end of the tube.
1.2.10
Couplant
Any material, usually a liquid or semiliquid, used between the search unit
and the inspection surface to exclude air and convey the ultrasonic
vibrations between the search unit and the material being inspected.
1.2.11
Damping Control
Control that varies the duration of transducer ringing.
1.2.12
Decibel (dB)
Units for the logarithmic expression of the ratio of power levels. Power
levels can be functions of voltage, current, or impedance. Decibel units
have no values of their own and are only significant when a reference is
stated, as 10 dB above one reference level or 6 dB below another reference
level.
1.2.13
Delay Control
Means of delaying the pattern obtained on the cathode ray tube.
SECTION 05092A
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