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

3.12: Arbitrary Function Generators
Arbitrary waveform generators permit the user to design and generate
virtually any waveform in addition to the standard function generator signals
(i.e. sine wave, square wave, etc.). Waveforms are generated digitally from a
computer's memory, and most instruments allow the downloading of digital
waveform files from computers.
Ultrasonic generation pulses must be varied to accommodate different types
of ultrasonic transducers. General-purpose highly damped contact
transducers are usually excited by a wideband, spike-like pulse provided by
many common pulser/receiver units. The lightly damped transducers used in
high power generation, for example, require a narrowband tone-burst
excitation from a separate generator unit. Sometimes the same transducer
will be excited differently, such as in the study of the dispersion of a material's
ultrasonic attenuation or to characterize ultrasonic transducers.