Views:6 Author:Site Editor Publish Time: 2019-02-16 Origin:Site
A ultrasonic transducer is a device that converts mechanical vibration into electrical signals or mechanical vibrations driven by an electric field. Piezoelectric polymer electroacoustic devices utilize the transverse piezoelectric effect of the polymer, while transducer design utilizes polymer piezoelectric.The bending vibration of a bimorph or piezoelectric single wafer driven by an external electric field can produce electroacoustic devices such as a microphone, a stereo earphone, and a tweeter using the above principles. At present, the research on piezoelectric polymer electroacoustic devices mainly focuses on the characteristics of piezoelectric polymers, and develops devices that are difficult to realize by other current technologies and have special electroacoustic functions, such as anti-noise telephones and broadband ultrasonic signal transmission systems.
Piezoelectric pressure sensors are made by using the piezoelectric effect of piezoelectric materials. The basic structure of the Pzt ceramic sensor is shown. Since the amount of charge of the piezoelectric material is constant, special care must be taken when connecting to avoid leakage. The piezoelectric pressure sensor has the advantages of self-generated signal, large output signal, high frequency response, small volume and firm structure. The disadvantage is that it can only be used for kinetic energy measurements. A special cable is required, and self-recovery is slow when subjected to sudden vibration or excessive pressure.
(2) Piezoelectric accelerometer sensor:
The piezoelectric ceramics element is generally composed of two piezoelectric wafers. Electrodes are plated on both surfaces of the piezoelectric wafer, and leads are drawn. A mass is placed on the piezoelectric wafer, and the mass is generally made of a relatively large metal tungsten or a high specific gravity alloy. The mass is preloaded with a hard spring or bolt, and the entire assembly is housed in a metal housing of the original base. In order to isolate any strain of the test piece being transmitted to the piezoelectric element to avoid false signal output, it is generally necessary to thicken the base or use a material with a relatively high rigidity. The weight of the housing and the base is almost the weight of the sensor. When is measuring, the sensor base and the test piece are rigidly fixed together. When the sensor is subjected to a vibration force, since the rigidity of the susceptor and the mass is relatively large, and the mass is relatively small, the inertia of the mass can be considered to be small. Therefore, the mass is subjected to the same motion as the susceptor and is subjected to an inertial force opposite to the direction of acceleration. Thus, the mass has a strain force proportional to the acceleration acting on the piezo cylinder ceramic transducer. Since the piezoelectric wafer has a piezoelectric effect, an alternating charge (voltage) is generated on its two surfaces. When the acceleration sensor is much lower than the natural frequency of the sensor, the output voltage of the sensor is proportional to the force, that is, It is proportional to the acceleration of the test piece. The output power is led out from the sensor output. After input of the preamplifier, the acceleration of the test piece can be tested with a common measuring instrument. If an appropriate integrating circuit is added to the amplifier, it can be tested. They are vibration speed or displacement of the test piece.