Due to the development of automation technology, pressure sensors commonly used in industrial equipment, in addition to liquid columns and elastic pressure gauges, generally use pressure transmitters and sensing devices, which can convert pressure into electrical signals. A pressure sensor is a sensor that converts pressure into electrical signal output. In general, the sensor is divided into two parts: photosensitive element and frequency converter.
The photosensitive element can directly sense or respond to the part being measured; it refers to the part of the measured strain that is sensed or reacted in the photosensitive element, converted into an electronic signal suitable for transmission or measurement. Because the sensor output signal is usually weak, it needs to be modulated and amplified. The development of integrated technology has prompted people to put this part of the circuit and power supply into the sensor again. In this way, the sensor is able to output a signal that is easy to process and transmittable. Generally speaking, a pressure force sensor refers to converting the changing pressure signal into a sensitive element, and correspondingly changing the resistance signal or capacitance signal.
The more widely used pressure sensors are: ceramic piezoresistive pressure sensors, sputtering film pressure sensors, capacitive pressure sensors, and high temperature sapphire pressure sensors. However, the most widely used is the piezoresistive pressure sensor, which has a very low price, high accuracy and good linearity characteristics. Below we introduce the classification of pressure sensors in detail.
1. Piezoresistive pressure sensor
Resistance strain gauge is one of the important components of piezoresistive strain sensor. The working principle of the strained electrical metal resistor is the strain resistance adsorbed on the base material and the resistance change during mechanical deformation. This phenomenon is called the resistance strain effect.
2. Ceramic pressure sensor
Based on the piezoresistive effect, this pressure acts directly on the front of the ceramic diaphragm, causing slight deformation of the diaphragm, and the thick film resistor is printed on the back. During the connection process of the Wheatstone bridge, due to the piezoresistance of the varistor effect, the bridge generates a voltage signal proportional to the pressure and proportional to the excitation voltage.
3. Diffused silicon pressure sensor
The working principle of the diffused silicon compressive load cell is also based on the piezoresistive effect. Using the piezoresistive effect principle, the pressure of the measured medium is directly acted on the sensor (stainless steel or ceramics), so that the film produces a micro-displacement proportional to the medium pressure, so that the The resistance value of the sensor changes, and the electronic circuit detects this change and converts the standard measurement signal corresponding to this pressure.
4. Piezoelectric pressure sensor
The piezoelectric effect is the main working principle of the piezoelectric sensor, and the piezoelectric sensor cannot be used for static measurement, because the charge after the external force is only saved when the loop has an infinite input impedance. This is not the case in reality, so this determines that the piezoelectric sensor can only measure dynamic stress.
5. Sapphire pressure sensor
Using the working principle of strain resistance type, using silicon-sapphire as the sensitive element, it has unparalleled measurement characteristics. Therefore, semiconductor sensitive components made of silicon sapphire are not sensitive to temperature changes, and have good performance even in high temperature environments; sapphire has excellent radiation resistance.
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