Ultrasonic transducer is an energy conversion device. Its function is to convert the input electrical power into mechanical power (ultrasound) and then transmit it out, and it consumes a small part of the power (less than 10%).
The structure of ultrasonic transducer:
The ultrasonic transducer in ultrasonic flow measurement can be divided into straight probe, oblique probe, and surface wave probe according to its structure. In this design, we choose an oblique probe as the ultrasonic transducer. The most commonly used transducer in ultrasonic flow detection is the piezoelectric oblique probe transducer, which is mainly composed of piezoelectric wafers, wedges, joints, etc., and is an important part of the ultrasonic flowmeter.
The transducer in the ultrasonic probe is usually made of piezoelectric wafer. The vibration frequency of the piezoelectric wafer is the working frequency of the probe, which mainly depends on the thickness of the wafer and the propagation speed of the ultrasonic wave in the wafer material. In order to obtain a higher frequency, the wafer is required to work in a resonance state, and the thickness of the wafer at this time is the wavelength.
Piezoelectric chip itself is relatively fragile. In order to protect it from damage when it is in contact with the workpiece, a protective film is often attached to the front of the chip. There is an oblique wedge in front of the wafer of the oblique probe. The longitudinal wave emitted from the wafer is directed to the surface of the test piece through a set oblique wedge of different inclination angles, and a transverse wave can be formed inside the test piece after the wave form conversion.
In order to increase the frequency of ultrasonic waves emitted by the probe, the wafer is often used in a resonance state, but this way the vibration is not easy to stop and it is difficult to form a narrow pulse. Therefore, damping blocks are often installed on the back of the wafer to increase the vibration damping of the wafer and absorb the ultrasonic waves emitted from the back of the wafer.
For inclined probes, the front of the chip has been fixed to the inclined surface of the wedge, and there is generally no damping block on the back. However, the multiple reflected waves in the wedge will cause a series of noise, so a damping material is poured in front of the wedge to absorb the noise.
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