Ultrasonic transducers are also called for ultrasonic probes. Ultrasonic transducers have piezoelectric, magnetostrictive, and electromagnetic types. By the detection technology, piezoelectric type is mainly used.Due to their different structures, the transducer is divided into a straight probe, an oblique probe, a double probe, a surface wave probe, a focusing probe, a flushing probe, and so on. In this paper, a solid conductive medium is taken as an example to briefly introduce the following three types of transducer for depth.
1.straight probe with single piezo crystal . Commonly known as a straight probe, its piezoelectric wafer is made of PZT piezoelectric ceramics. When transmitting ultrasonic waves have a high-voltage electric pulse of 500V or more is applied to the piezoelectric wafer, and the reverse piezoelectric effect is used to cause the wafer to emit an ultrasonic vibration wave whose frequency falls within the ultrasonic range transducer and has a short duration, and is vertically projected to inside the test . It is assumed that the test is a steel plate, and the bottom surface is in contact with the air, and most of the ultrasonic energy is reaching the bottom of the steel plate,reflected by the bottom interface. The reflected wave returns to the piezoelectric wafer after a short propagation time.By using the piezoelectric effect, the piezoelectric wafer converts the mechanical vibrational waves into alternating charges and voltages of the same frequency ultrasonic flowmeter transducer. .
2.straight probe with double crystal . It is a combination of two single piezo crystal probes assembled in the same housing material, one of which emits ultrasonic waves and the other of which receives ultrasonic waves. Although the structure of the dual piezoelectric crystal probe is more complicated, the detection accuracy of transducer for gas meter is higher than that of the straight probe with single crystal , and the control circuit for the reflection and reception of the ultrasonic signal is simpler than the straight probe with single crystal .
3.Oblique probe. Sometimes, in order to make the ultrasonic energy obliquely incident on the measuring medium, an oblique probe may be selected. The transducer for ultrasonic welding piezoelectric wafer is attached to a plexiglass wedge that is angled to the bottom surface. When the wedge is in contact with the measuring medium of different materials, the ultrasonic wave produces a certain angle of refraction, obliquely incident into the test piece, and the angle of refraction can pass.
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