Views:96 Author:Site Editor Publish Time: 2020-09-08 Origin:Site
Some crystals deform when subjected to a certain direction of external force, which causes the internal lattice spacing to change, and the positive and negative charge centers of the crystal grains are separated to form a polarization phenomenon. At the same time, the same amount appears on the two surfaces of the force. Anisotropic charge. The polarization charge generated by pulling force is opposite to the polarization charge generated by pressure. When the external force is removed, it will return to the original uncharged state. This phenomenon of converting mechanical energy into electrical energy is called the piezoelectric effect, also known as the paraelectric effect or the positive piezoelectric effect. In addition, when a force is applied When the direction changes, the polarity of the charge also changes. The amount of charge generated by the dielectric force is proportional to the magnitude of the external force.
The piezoelectric effect was discovered in 1880 by the famous French physicists Pierre Curie and Jacques Paul Curie. In the beginning, Pierre devoted himself to the study of the relationship between the pyroelectric phenomenon and the symmetry of crystals. In the end, the brothers discovered that the pressure on a certain type of dielectric will produce electricity. They systematically studied the relationship between the pressure direction and the electric field strength and predicted that a certain type of dielectric has a piezoelectric effect.
1) Force-sensitive sensor: measurable such as force, pressure acceleration, etc.
2) Vibration and shock sensors: seismometers, machinery, bridges, and buildings.
3) Ultrasonic sensor: sonar system.
4) Piezoelectric microphone.
5) Ignition device: lighter, gas stove igniter, shell detonation.
As the name implies, it is just the opposite of the positive piezoelectric effect. When we apply an electric field in the polarization direction of the crystal, the crystal lattice in these crystals will undergo strong internal stress and deform under the action of the electric field force. Under the action of the variable electric field, its internal stress and deformation will undergo periodic changes, resulting in mechanical vibration. When the electric field disappears, the deformation of the crystal also disappears. This phenomenon of converting electrical energy into mechanical energy is called the inverse piezoelectric effect, also known as the phenomenon of electrical contraction.
1) Ultrasonic humidifier.
2) Ultrasonic cleaning machine.
3) Piezoelectric buzzer.
If the pressure is applied to the piezoelectric ceramic, it will produce a potential difference, which is called the positive piezoelectric effect. On the contrary, applying voltage will produce mechanical stress, which is called the inverse piezoelectric effect. If the pressure is a high-frequency vibration, it will produce a high-frequency current. When high-frequency electrical signals are applied to piezoelectric ceramics, high-frequency acoustic signals are generated, that is, mechanical vibration. This is what we usually call an ultrasonic signal. In other words, piezoelectric ceramics have the function of conversion and reverse conversion between mechanical energy and electrical energy.
Commonly used piezoelectric ceramics are made of lead zirconate titanate (PZT) material. Piezoelectric ceramic elements are formed by sticking piezoelectric ceramic sheets made of PZT material on a round brass sheet. It has an obvious piezoelectric effect. The connection is as follows:
First, connect the two leads of the piezoelectric ceramic sheet A to the signal generator S through a button switch. Connect the two leads of the piezoelectric ceramic sheet B to the input end of the amplifier (with horn). Fix the two piezoelectric ceramic pieces A and B on a box made of the same wooden board with black sealing mud. When the observer presses the button switch to switch on the signal generator and piezoelectric ceramic A, due to the inverse piezoelectric effect, A starts to vibrate and transmits the vibration to the wooden box, and the vibration of the wooden box is transmitted to the piezoelectric ceramic B. Due to the piezoelectric effect, electrical signals are generated on both sides of B, which are then transmitted to the loudspeaker to make the horn sound. This experiment demonstrates both the piezoelectric effect and the inverse piezoelectric effect.
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