Last Updated on June 16, 2021 by You Ling
Ultrasonic piezoelectric transducer
Ultrasonic piezoelectric transducer is a device that converts electromagnetic energy into mechanical energy (sound energy). It is made of piezoelectric ceramic material. Common ultrasonic atomizer, ultrasonic cleaner, B-ultrasonic probe and so on are all application examples of ultrasonic piezoelectric transducers.
Before talking about ultrasonic piezoelectric transducers, we should first understand the piezoelectric ceramics, the core material of which transducers are made. Piezoelectric ceramic is a kind of electronic ceramic material with information function which can convert mechanical energy and electric energy into each other. Therefore, piezoelectric ceramics have been widely used in ultrasonic transducers for nearly 50 years.
The theory of ultrasonic piezoelectric transducer: ultrasonic transducer with the help of piezoelectric ceramic resonant in ultrasonic frequency, by the piezoelectric effect of piezoelectric ceramic material to convert electromagnetic signals into mechanical vibration. Specifically, various ultrasonic transducers work in much the same way.
The following is to describe the medical ultrasonic piezoelectric transducer as an example. The working principle of medical ultrasonic transducer (ultrasonic probe) usually contains an electrical energy storage element and a mechanical vibration system. When in ultrasound can be used as emitter, electrical oscillation signal from excitation power supply will cause the ultrasonic transducer CLP energy storage element in the change of the electric field or magnetic field, the effect of this change by some on the transducer of the mechanical vibration system to produce a driving force, to make it into the oscillating regime, so as to promote with the transducer of the medium in contact with the mechanical vibration system vibration, the radiation sound wave in the medium. Receiving sound waves is just on the contrary, the process of suppressing effect on the vibration of the transducer, so that mechanical vibration system vibration transducer, with the help of some physical effect, cause transducer corresponding changes in the energy storage components of the electric field or magnetic field, that cause the transducer’s electricity output to produce a corresponding to acoustic signal voltage and current. Usually, the transmitting and receiving signals of ultrasonic transducer are carried out simultaneously.
The structure of medical ultrasonic transducer is as follows:
Piezoelectric ceramic crystal is the main functional part, used to transmit and receive ultrasonic wave, to complete the acoustic-electric and electric-acoustic conversion work. The geometry and dimensions are designed according to diagnostic requirements. Because the piezoelectric crystal is brittle and requires insulation, sealing, corrosion prevention, etc., piezoelectric crystal must be loaded into the shell.
The two ends of the piezoelectric crystal are plated with electrodes, and the upper and lower electrodes are respectively welded with a lead wire, which is connected with the electrode plug-in on the shell to transmit electrical signals.
Gasket (also known as the sound-absorbing material absorption, sound absorption blocks) for attenuation and absorption of piezoelectric crystals toward the ultrasonic energy of radiation, so not in the probe bounces back and forth and make the crystal ringing time extended, so the gasket has a larger damping ability, and have and close to the acoustic impedance of piezoelectric materials, so that the sound waves from piezoelectric crystal back to radiation all into pad and no longer reflect back to crystal absorption material for epoxy resin, tungsten powder, or ferrite powder and rubber powder.
Acoustic insulation layer, prevent ultrasonic energy to probe housing caused by reflection, resulting in interference to the signal.
The protective layer is used to protect the vibrator from abrasion. Because the protective layer is in contact with the vibrator and the human tissue at the same time, it is a layer of material between the vibrator and the human tissue. It is required that the protective layer not only plays the function of preventing wear and protection of the vibrator, but also has the good transmission function without attenuation in the transmission of ultrasonic wave.Therefore, it is required that the acoustic impedance of the protective layer is close to the acoustic impedance of human tissue, and has the optimal thickness of both wear resistance and good transmission.The protective layer should be made of materials with low attenuation coefficient and wear resistance. The protective layer should also be used as an acoustic impedance gradient layer for the interbedded insertion.
As the supporting body of the internal material of the probe, the shell plays the role of supporting, accommodating, sealing, insulating, pressure bearing, shielding and protecting the vibrator, and is used to fix the cable lead. The model and nominal frequency of the probe are usually marked on the shell.
Sometimes the enclosure is equipped with an impedance converter, a prime amplifier, a damping resistor and a regulating inducer and other accessories.
If you are interested in learning more about piezoelectric ceramics, please read the piezoelectric ceramics blog post or contact us