Pressure sensors are among the most widely used types of sensors. Traditional pressure sensors are primarily mechanical devices that indicate pressure through the deformation of elastic elements. However, this type of structure is large, heavy, and cannot provide electrical output. With the development of semiconductor technology, semiconductor pressure sensors have emerged. Their characteristics include small size, light weight, high accuracy, and good temperature characteristics. Especially with the development of MEMS technology, semiconductor sensors are becoming increasingly miniaturized, and their power consumption and reliability are also improving.
Introduction to the working principles of several common pressure sensors
1. Piezoresistive pressure sensor
Resistance strain gauges are one of the main components of piezoresistive strain sensors. The working principle of a metal resistance strain gauge is based on the phenomenon that the resistance of the strain gauge adsorbed on the substrate material changes with mechanical deformation, commonly known as the resistance strain effect.
2. Ceramic pressure sensor
Ceramic pressure sensors are based on the piezoresistive effect. Pressure acts directly on the front surface of a ceramic diaphragm, causing a slight deformation of the diaphragm. A 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 piezoresistive resistor, the bridge generates a highly linear voltage signal that is proportional to the pressure and also proportional to the excitation voltage. The standard signal is calibrated to 2.0/3.0/3.3mV/V, etc., depending on the pressure range, and is compatible with strain gauge sensors.
3. Diffused silicon pressure sensor
The working principle of diffused silicon pressure sensors is also based on the piezoresistive effect. Utilizing the piezoresistive effect, the pressure of the measured medium acts directly on the diaphragm of the sensor (stainless steel or ceramic), causing the diaphragm to produce a micro-displacement proportional to the medium pressure. This causes a change in the resistance value of the sensor, which is detected by electronic circuitry and converted into a standard measurement signal corresponding to that pressure.
4. Sapphire pressure sensor
Utilizing the strain gauge principle and employing silicon-sapphire as the semiconductor sensing element, it possesses unparalleled metrological characteristics. Therefore, semiconductor sensing elements made using silicon-sapphire are insensitive to temperature changes and exhibit excellent operating characteristics even under high-temperature conditions; sapphire has strong radiation resistance; furthermore, silicon-sapphire semiconductor sensing elements exhibit no pn drift.
5. Piezoelectric pressure sensor
The piezoelectric effect is the main working principle of piezoelectric sensors. Piezoelectric sensors cannot be used for static measurements because the charge generated after an external force is applied is only preserved when the circuit has infinite input impedance. This is not the case in reality, which means that piezoelectric sensors can only measure dynamic stress.
