Working Principle of Piezoelectric Pressure Sensors and Charge Generation Mechanism of Piezoelectric Materials

Piezoelectric pressure sensor uses piezoelectric effect to measure pressure, and its working principle involves the charge change of piezoelectric material when it is subjected to pressure. The following is a detailed explanation of how piezoelectric pressure sensors use the piezoelectric effect to measure pressure and how the internal piezoelectric material generates an electrical charge:  

1. Principle of piezoelectric effect:  

When piezoelectric materials are subjected to external pressure, their crystal structure will undergo a slight deformation. This deformation causes the positive and negative charge centers inside the crystal to no longer coincide, resulting in a potential difference between the two ends of the crystal, the so-called piezoelectric field.  

Piezoelectric effect is divided into direct piezoelectric effect and inverse piezoelectric effect. Positive piezoelectric effect refers to the phenomenon that piezoelectric materials produce electric charges when they are subjected to external forces, while reverse piezoelectric effect refers to the tiny deformation of piezoelectric materials when an electric field is applied to them. Piezoelectric effect is mainly used in piezoelectric pressure sensors.  

2. How the internal piezoelectric material generates charge: 

Take quartz as an example. Quartz is a natural crystal with piezoelectric effect. When quartz is subjected to pressure, the silicon-oxygen bonds in its crystal structure are slightly deformed, causing the positive and negative charge centers to no longer coincide. This deformation creates a potential difference across the quartz crystal, known as a piezoelectric field. Under the action of the electric field, electrons will move from one end to the other, thus generating charges of opposite polarity on the two electrodes.  

Ceramic materials also have a piezoelectric effect. Unlike quartz, the piezoelectric effect of ceramic materials is obtained by artificial doping and polarization processes. In ceramic materials, the crystal structure is changed by doping specific ions, and the ceramic materials have piezoelectric properties through the high-temperature polarization process. When a ceramic material is subjected to pressure, its crystal structure is also deformed, resulting in piezoelectric fields and charges.  

3. Measurement process of piezoelectric pressure sensor:  

When the piezoelectric pressure sensor is subjected to external pressure, its internal piezoelectric material will generate piezoelectric field and charge. These charges are amplified and converted by the charge amplifier and the measuring circuit into an electrical output signal proportional to the external force. By measuring the magnitude of this electrical output signal, the magnitude of the external pressure can be known.  

Piezoelectric pressure sensor has the advantages of wide frequency band, high sensitivity, high signal-to-noise ratio, simple structure and reliable operation. However, since some piezoelectric materials require moisture protection and have poor output DC response, a high input impedance circuit or charge amplifier is required to overcome these disadvantages.