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

Instrument Circuitry: Signal-conditioning and gating
circuits are included in many commercial ultrasonic instruments. One
common example of a signal-conditioning feature is a circuit that
electronically compensates for the signal-amplitude loss caused by
attenuation of the ultrasonic pulse in the test piece. Electronic gates, which
monitor returning signals for pulses of selected amplitudes that occur within
selected time-delay ranges, provide automatic interpretation. The set point of
a gate corresponds to a flaw of a certain size that is located within a
prescribed depth range. Gates are often used to trigger alarms or to operate
automatic systems that sort test pieces or identify rejectable pieces.