What is the fraction of time that a transducer is transmitting?

• A. Pulse duration
• B. Period
• C. Duty factor
• D. PRF

Answer: (C)

Duty factor is the fraction of time the transducer is emitting. It’s defined as pulse duration divided by the period, and is often shown as a percentage. For example, if a pulse lasts 2 μs and the time between starts of successive pulses (the period) is 100 μs, the duty factor is 2/100 = 0.02, or 2%. The pulse duration is simply how long each individual pulse lasts, while the period is the total time for one complete on-and-off cycle. The PRF is the number of pulses emitted per second, which is the reciprocal of the period. Since the question asks for the portion of time the transducer is transmitting, that fraction is the duty factor.