what is pressure sensor and how it works

Pressure sensor is the most commonly used sensor in industry.It is widely used in various industrial automation environments, involving water conservancy and hydropower, railway transportation, intelligent buildings, production automation, aerospace, military, petrochemical, oil well, electric power, ships, machine tools, pipelines and many other industries。The following briefly introduces some common sensor principles and their applications.

Use and setting of pressure sensor

Two-wire pressure sensor, one wire is connected to the positive pole of the power supply, and the other wire is the signal wire connected to the negative pole of the power supply through the instrument. This is the simplest.The three-wire pressure sensor is a line added to the two-wire system. This line is directly connected to the negative pole of the power supply, which is a bit more troublesome than the two-wire system.The four-wire pressure sensor has two power input terminals, and the other two are signal output terminals.Most of the four-wire system is voltage output instead of 4-20mA output. The 4-20mA is called pressure transmitter, and most of them are made into two-wire system.The signal output of some pressure sensors is not amplified, and the full-scale output is only tens of millivolts, while some pressure sensors have an internal amplifier circuit, and the full-scale output is 0~2V.As for how to connect to the display instrument, it depends on the range of the instrument.If there is a gear suitable for the output signal, it can be measured directly, otherwise a signal adjustment circuit must be added.The five-wire pressure sensor is not much different from the four-wire system, and there are fewer five-wire sensors on the market.

一、Principle of pressure sensor：

1：Piezoresistive pressure sensor: Resistance strain gauge is one of the main components of piezoresistive strain sensor.The working principle of the metal resistance strain gauge is the phenomenon that the resistance value changes with the mechanical deformation of the strain resistance adsorbed on the base material, commonly known as the resistance strain effect.

2.Ceramic pressure sensor: The ceramic pressure sensor is based on the piezoresistive effect. The pressure directly acts on the front surface of the ceramic diaphragm, causing a slight deformation of the diaphragm. The thick film resistor is printed on the back of the ceramic diaphragm and connected to form a Wheatstone bridge.Due to the piezoresistive effect of the varistor; the bridge generates a highly linear voltage signal proportional to the pressure and proportional to the excitation voltage。The standard signal is calibrated to 2.0/3.0/3.3mV/V, etc. according to the different pressure ranges, which can be compatible with strain gauge sensors.

3.Diffused silicon pressure sensor: The working principle of the diffused silicon pressure sensor is also based on the piezoresistive effect. Using the principle of piezoresistive effect, the pressure of the measured medium directly acts on the diaphragm of the sensor, so that the diaphragm produces a microstructure proportional to the pressure of the medium. Displacement changes the resistance of the sensor. The electronic circuit detects this change and converts and outputs a standard measurement signal corresponding to this pressure.

4.Sapphire pressure sensor: Utilizes the working principle of strain resistance and uses silicon-sapphire as the semiconductor sensitive element, which has unparalleled measurement characteristics.Therefore, semiconductor sensitive components made of silicon-sapphire are not sensitive to temperature changes and have good working characteristics even under high temperature conditions; sapphire has extremely strong radiation resistance; in addition, silicon-sapphire semiconductor sensitive components are not sensitive to temperature changes. pn drift.

5.Piezoelectric pressure sensor: The piezoelectric effect is the main working principle of the piezoelectric sensor. The piezoelectric sensor cannot be used for static measurement, because the charge after the action of external force can only be obtained when the circuit has infinite input impedance save. The actual situation is not like this, so this determines that the piezoelectric sensor can only measure dynamic stress.