Pressure sensors are one of the most commonly used sensors in industrial practice, and the pressure sensors that we commonly use are primarily fabricated using piezoelectric effects. Such sensors are also known as piezoelectric sensors.
We know that crystals are anisotropic and noncrystals are isotropic. Some crystal media, when deformed by a mechanical force along a certain direction, produce a polarization effect; when the mechanical force is removed, it will return to the uncharged state, that is, when the pressure is applied. Some crystals may produce an electrical effect. This is the so-called polarization effect. Scientists developed a pressure sensor based on this effect.
Piezoelectric materials mainly used in piezoelectric sensors include quartz, sodium potassium tartrate, and diammonium phosphate. Among them, quartz (silicon dioxide) is a kind of natural crystal. The piezoelectric effect is found in this kind of crystal. Within a certain temperature range, the piezoelectricity is always there, but after the temperature exceeds this range, the piezoelectricity is completely Disappear (this high temperature is the so-called "curie point"). Because the electric field changes little with the change of stress (that is, the piezoelectric coefficient is relatively low), quartz is gradually replaced by other piezoelectric crystals. Potassium sodium tartrate has a large piezoelectric sensitivity and piezoelectric coefficient, but it can only be applied in environments with low room temperature and low humidity. Dihydrogen phosphate is an artificial crystal that can withstand high temperatures and high humidity, so it has been widely used.
Piezoelectric effect is also applied to polycrystals, such as current piezoelectric ceramics, including barium titanate piezoelectric ceramics, PZT, niobate piezoelectric ceramics, lead magnesium niobate piezoelectric ceramics, and the like.
Piezoelectric effect is the main working principle of piezoelectric sensor. Piezoelectric sensor cannot be used for static measurement because the charge after external force is only saved when the loop has infinite input impedance. The actual situation is not like this, so this determines that the piezoelectric sensor can only measure the dynamic stress.
Piezoelectric sensors are mainly used in the measurement of acceleration, pressure, and force. Piezoelectric acceleration sensor is a commonly used accelerometer. It has the advantages of simple structure, small size, light weight and long service life. Piezoelectric accelerometers have been widely used in the measurement of vibration and shock in aircrafts, automobiles, ships, bridges, and buildings, especially in the aviation and aerospace fields. Piezoelectric sensors can also be used to measure the internal combustion pressure measurement and vacuum measurement. It can also be used in the military industry, for example, to measure the momentary pressure change of a shotgun bullet fired in a raft and the shock wave pressure of the muzzle. It can be used to measure large pressures, but it can also be used to measure tiny pressures.
Piezoelectric sensors are also widely used in biomedical measurements. For example, ventricular catheter microphones are made of piezoelectric sensors, because the measurement of dynamic pressure is so common, so the application of piezoelectric sensors is very wide.
In addition to piezoelectric sensors, there are piezoresistive sensors manufactured using piezoresistive effects, strain sensors using strain effects, etc. These different pressure sensors utilize different effects and different materials and can exert them on different occasions. Unique use.