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

Instrument Circuitry: Clock
The clock circuit initiates a chain of events that results in one complete cycle
of a UT examination. The clock sends a trigger signal, at a regular interval, to
both the (1) time base and to the (2) pulser. As the name “clock”' implies, this
trigger signal is repeated at a given frequency, called the pulse repetition rate
(PRR). On some instruments pulse repetition rate is adjustable by the
examiner; other instruments do it automatically. The electronic clock, or timer,
serves as a source of logic pulses, reference voltage, and reference
waveform. The clock coordinates operation of the entire electronic system.