Preparatory Notes for ASNT NDT Level III Examination - Ultrasonic Testing, UT

Precision ultrasonic thickness gages usually operate at frequencies between
500 kHz and 100 MHz, by means of piezoelectric transducers that generate
bursts of sound waves when excited by electrical pulses. A wide variety of
transducers with various acoustic characteristics have been developed to
meet the needs of industrial applications. Typically,
1. lower frequencies are used to optimize penetration when measuring thick,
highly attenuating or highly scattering materials,
2. while higher frequencies will be recommended to optimize resolution in
thinner, non-attenuating, non-scattering materials.
0.5 MHz ~ 100 MHz