This invention discloses a gas-liquid detection device, method, and
system based on the near-field load characteristics of an ultrasonic
transducer, belonging to the field of
underwater state monitoring and ultrasonic sensing technology. The device includes: an ultrasonic
transducer that emits ultrasonic vibrations and receives near-field electroacoustic response signals; an excitation circuit that applies a pulse
excitation signal to the ultrasonic
transducer; an acquisition circuit that acquires near-field
free oscillation signals at both ends of the ultrasonic transducer within a preset time window after the excitation ends; and a
signal processing module that extracts time-domain feature parameters from the acquired near-field
free oscillation signals, compares the extracted feature parameters with a preset threshold, and outputs a state indicator indicating whether the ultrasonic transducer is currently in a gaseous or
liquid medium. The time-domain feature parameters are used to characterize the amplitude or attenuation characteristics of the near-field
free oscillation signal. This invention requires only a single ultrasonic transducer, eliminating the need for a reflective surface or dual transducers, and has advantages such as simple structure, strong anti-interference capability, fast response speed, low
power consumption, and high detection accuracy.