Principle of Piezoelectric Pressure Sensor

The piezoelectric sensor is composed of piezoelectric sensing element and measurement conversion circuit. It is a sensor based on the piezoelectric effect. Self-electric and electro mechanical conversion sensors. The surface of a piezoelectric material is charged when it is stressed. The charge is amplified and the impedance transformed by the charge amplifier and the measuring circuit to become the electrical output proportional to the external force. Piezoelectric sensors are used to measure non-electrical physical quantities of force and energy converted into electricity.

The piezoelectric effect refers to the fact that certain crystals produce electrical charges when subjected to mechanical stress, which is called a piezoelectric crystal. Common piezoelectric crystals are quartz, piezoelectric ceramics and so on. In a piezoelectric pressure sensor, the piezoelectric crystal is fixed to the bottom of the sensor, and when the force is applied, the piezoelectric crystal at the bottom will generate an electric charge.

Piezoelectric pressure sensors are usually composed of four main parts: piezoelectric crystal, mechanical structure, circuit and output signal. The mechanical structure is used to transfer the pressure of the object to the piezoelectric crystal while protecting the crystal from damage. The circuit converts the electric charge generated by the piezoelectric crystal into a voltage signal, and the output signal converts the voltage signal into a physical quantity that people can understand, such as a pressure value.

In the application of piezoelectric pressure sensor, it is necessary to consider the sensitivity and linearity of the sensor. Sensitivity refers to the ratio between the change in the output signal of the sensor and the change in the input signal, usually expressed by the output voltage under a unit load. Linearity refers to whether the relationship between the sensor output signal and the input signal is linear, that is, whether there is nonlinear error.

There are many types and models of piezoelectric pressure sensors, which can be divided into diaphragm type and piston type according to the form of elastic sensitive elements and stress mechanisms. Diaphragm type is mainly composed of body, diaphragm and piezoelectric element. The piezoelectric element is supported on the body, and the measured pressure is transmitted to the piezoelectric element by the diaphragm, and then the electrical signal is output by the piezoelectric element which has a certain relationship with the measured pressure. The sensor is characterized by small size, good dynamic characteristics, high temperature resistance and so on. Modern measurement technology demands more and more high performance of sensors.

Piezoelectric pressure sensors are widely used in industry, medical treatment, aviation and other fields. In the industrial field, piezoelectric pressure sensors can be used to measure the pressure of mechanical equipment, liquid or gas pressure. In the medical field, piezoelectric pressure sensors can be used to detect physiological signals such as blood pressure and pulse. In the field of aviation, piezoelectric pressure sensors can be used to measure information such as air pressure and wind speed of aircraft.

The piezoelectric materials mainly used in piezoelectric pressure sensors include quartz, sodium potassium tartrate, and dihydrogen phosphate. Among them, quartz|silica is a kind of natural crystal. The piezoelectric effect is found in this crystal. The piezoelectric property always exists within a certain temperature range, but after the temperature exceeds this range, the piezoelectric property completely disappears. . High temperature is the so-called Curie point. Since the electric field changes little with the change of stress, that is, the piezoelectric coefficient is low, quartz is gradually replaced by other piezoelectric crystals. The piezoelectric effect is applied to polycrystals, such as piezoelectric ceramics, including barium titanate piezoelectric ceramics, PZT, tantalate-based piezoelectric ceramics, lead magnesium niobate piezoelectric ceramics, and the like.

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