Pressure sensors are the most commonly used sensors in industrial practice, and the pressure sensors we usually use are mainly made by the piezoelectric effect. Such sensors are also called piezoelectric sensors.
We know that crystals are anisotropic and amorphous are isotropic. Some crystal media, when deformed by mechanical force in a certain direction, have a polarization effect; when the mechanical force is removed, it will return to the uncharged state, that is, when subjected to pressure, These crystals may produce an electricity output effect, which is called the polarization effect. Scientists have developed pressure sensors based on this effect.
Piezoelectric materials mainly used in piezoelectric sensors include quartz, sodium potassium tartrate, and dihydrogen phosphate. Among them, quartz 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 (this 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 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 a low room temperature and humidity environment. Dihydrogen phosphate is an artificial crystal that can withstand high temperatures and relatively high humidity, so it has been widely used.
The piezoelectric effect is the main working principle of the piezoelectric sensor. The piezoelectric sensor cannot be used for static measurement, because the electric charge after the external force is saved only when the loop has an infinite input impedance. This is not the case, so this determines that the piezoelectric sensor can only measure dynamic stresses.
Piezoelectric sensors are mainly used in the measurement of acceleration, pressure and force. A piezoelectric accelerometer is a commonly used accelerometer. It has the characteristics of simple structure, small size, light weight and long service life. Piezoelectric accelerometers have found wide application in vibration and shock measurements in aircraft, automobiles, ships, bridges and buildings, especially in the aerospace and aerospace fields. Piezoelectric sensors can also be used to measure the measurement of combustion pressure inside the engine and the measurement of vacuum.
