The invention relates to the technical field of sensors, and discloses a multi-resonant-frequency
partial discharge ultrasonic sensor, which comprises a capillary
glass tube, an
optical fiber collimating mirror arranged in the capillary
glass tube, and a diaphragm arranged at the end part of one side of the capillary
glass tube, the capillary glass tube is provided with an
optical fiber matching liquid containing cavity, the
optical fiber matching liquid containing cavity is located between the optical
fiber collimating mirror and the diaphragm, optical
fiber matching liquid is contained in the optical
fiber matching liquid containing cavity, a set of
cantilever beams extending towards the center position are installed in the optical fiber matching liquid containing cavity, and the
cantilever beams and the diaphragm are plated with reflecting films with certain
reflectivity. The optical fiber collimating mirror is connected with the coupler through an optical fiber line penetrating through the capillary glass tube, the coupler is connected with the driving
light source and the photoelectric converter, and the photoelectric converter is connected with the
data acquisition terminal. According to the invention, a
Michelson interferometer principle is utilized, three
resonance detection frequency bands are copolymerized, and a detected ultrasonic
signal is restored through the change of
light intensity, so that the
cantilever beam diaphragm can detect a
partial discharge ultrasonic
signal; and meanwhile, a common-
path design is adopted, so that the problem of
thermal expansion and contraction of an
optical path caused by temperature can be counteracted, and the influence of temperature is eliminated.