Principle and application of piezoelectric pressure sensor

Principle and application of piezoelectric pressure sensor

The main piezoelectric materials used in piezoelectric sensors include quartz, potassium sodium tartrate and dihydroamine phosphate. Quartz (silica) is a natural crystal, and the piezoelectric effect is found in this crystal. Within a certain temperature range, the piezoelectric property always exists, but after the temperature exceeds this range, the piezoelectric property disappears completely (this high temperature is the so-called "Curie point"). Because the electric field changes slightly 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 great piezoelectric sensitivity and piezoelectric coefficient, but it can only be used at room temperature and low humidity. Dihydroamine phosphate is an artificial crystal, which can withstand high temperature and high humidity, so it has been widely used.

Now piezoelectric effect is also applied to polycrystals, such as piezoelectric ceramics, including barium titanate piezoelectric ceramics, PZT, niobate piezoelectric ceramics, lead magnesium niobate piezoelectric ceramics and so on.

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 saved only when the circuit has infinite input impedance. The actual situation is not like this, so this determines that the piezoelectric sensor can only measure dynamic stress.

Piezoelectric sensors are mainly used in the measurement of acceleration, pressure and force. Piezoelectric accelerometer is a common accelerometer. It has the advantages of simple structure, small volume, light weight and long service life. Piezoelectric acceleration sensor has been widely used in vibration and impact measurement of aircraft, automobiles, ships, bridges and buildings, especially in the field of aviation and aerospace. The piezoelectric sensor can also be used to measure the combustion pressure and vacuum inside the engine. It can also be used in military industry. For example, it can be used to measure the change of chamber pressure at the moment when a gun bullet is fired in the chamber and the shock wave pressure at the muzzle. It can be used to measure both large pressure and small pressure.

Piezoelectric sensors are also widely used in biomedical measurement. For example, ventricular catheter microphone is made of piezoelectric sensors. Because measuring dynamic pressure is so common, piezoelectric sensors are widely used

Fl-1151 series pressure transmitter

The process pressure passes through the isolation diaphragm on both sides or one side, and the filling liquid acts on δ On the tensioned measuring diaphragm in the element (i.e. sensitive element), the measuring diaphragm and the capacitor plates on the insulators on both sides form a capacitor respectively. When there is no pressure or the pressure on both sides is equal, the measuring diaphragm is in the middle position, and the capacitance of the two capacitors is equal When the pressures on both sides are inconsistent, the measuring diaphragm will produce displacement, which is directly proportional to the pressure difference. This displacement will be transformed into the differential capacitance formed on the capacitor plate The electronic circuit converts the differential capacitance into a two-wire current signal of 4-20madc. The working principle of pressure transmitter and absolute pressure transmitter is the same as that of differential pressure transmitter, except that the pressure of low-pressure chamber is atmospheric pressure or vacuum. Position influence

The zero position system error of no more than 0.24kpa may be generated, which can be eliminated by adjusting the zero position and has no impact on the measuring range.