what is piezoelectric pressure transducer

                             what is piezoelectric pressure transducer

 If two elongated piezo ceramic plates of the same thickness and polarization are bonded together, bending vibration of ultrasonic plate transducer can occur when one of the two is stretched and the other is shortened by applying an exciting electric field. As shown in Figure 3a, the two ceramic wafers are bonded are polarized in the opposite direction and connected in series to the power supply. Figure 3b shows the parallel connection of two piezo ring electric sensor with the same polarization direction. In both ceramic adhesive sheets, only one of the electric fields is excited to generate bending vibration. Similarly, the bonding of two piezoelectric ceramic sheets to one thin metal sheet or bonding of one ceramic sheet to one thin metal sheet can also generate bending vibration.

 The relationship between the resonant frequency fr of the thickness bending vibration mode and the length l of the sheet and the total thickness t of the adhesive sheet is that where N lt is a frequency constant. Thickness vibration mode of piezo sphere sensor is suitable for the frequency range of 500 Hz to 100 kHz. The size of this kind of vibrator is generally (k is the width of the ceramic piece). The characteristic of the thickness shear vibration mode is that the electrode surface is parallel to the polarization direction. Under the action of the alternating electric field, the piezo ceramic generates the shear vibration in the thickness direction. The thickness shear mode of high temperature piezo transducer is relatively easy to be excited and is mainly used in the high frequency range of 10 to 60 kHz, and will not be described here in detail. In the ultrasonic distance meter, the piezoelectric transducer emits ultrasonic waves, and the vibration amplitude of the transducer is required to be large. Therefore, it is preferable to adopt a bending vibration mode piezo bimorph for comprehensive acoustic. At the same time, since the acoustic impedance of air is extremely low, it is impossible for a typical piezoelectric material to achieve impedance matching with it, and therefore it must also be realized by means of a transition layer.

 It was found that the piezoelectric ceramic sheet and the thin metal sheet are bonded together. Using the piezoelectric ceramic as the excitation source, a bending vibration mode can be generated, a larger amplitude is obtained, and the acoustic impedance of Hifu piezo for therary device is smaller, and the acoustic impedance matching with air can be achieved. . This article is the use of ceramic sheet and thin metal sheet bonded structure form, its schematic diagram shown in the Figure 4. The thin metal sheet can also act as a protective film,which is protecting the piezoelectric ceramics and electrodes, preventing wear and damage. Its material can use high stability nickel chromium titanium alloy. Since the metal sheet is thinner, the sound pressure reciprocal transmission rate is larger, so the metal sheet is designed to be very thin, generally about 0.1 mm.