Briefly talk about the working principle of pressure sensor

Working Principle of Pressure Sensor

1. Principle of Strain Gauge Pressure Sensor

There are many types of mechanical sensors, such as resistance strain gauge pressure sensors and semiconductor strain gauge pressure sensors. , Piezoresistive pressure sensors, inductive pressure sensors, capacitive pressure sensors, resonant pressure sensors and capacitive acceleration sensors, etc.

Resistance strain gauge is a sensitive device that converts the strain change on the measured piece into an electrical signal. The most commonly used resistance strain gauges are metal resistance strain gauges and semiconductor strain gauges. Usually, the strain gauge is tightly bonded to the base that generates mechanical strain through a special adhesive. When the base body is stressed and undergoes stress changes, the resistance strain gauge also deforms, causing the resistance of the strain gauge to change. The voltage across the resistor changes. Generally, such strain gauges form a strain bridge and are amplified by subsequent instrumentation amplifiers, and then transmitted to the processing circuit (usually A/D conversion and CPU) for display or actuator.

2. Principle of ceramic pressure sensor

The pressure of the ceramic pressure sensor directly acts on the front surface of the ceramic diaphragm, causing the diaphragm to undergo slight deformation. The thick film resistor is printed on the ceramic diaphragm. The back side of the resistor is connected to form a Wheatstone bridge (closed bridge). Due to the piezoresistive effect of the varistor, the bridge generates a voltage signal proportional to the pressure.

3. Principle of diffused silicon pressure sensor

Working principle: The pressure of the measured medium directly acts on the diaphragm of the sensor (stainless steel or ceramic), causing the diaphragm to generate pressure with the medium The proportional micro-displacement changes the resistance value of the sensor. The electronic circuit is used to detect this change and convert and output a standard measurement signal corresponding to this pressure.

4. Sapphire pressure sensor

Using the strain resistance working principle and using silicon-sapphire as the semiconductor sensitive element, it has good measurement characteristics.

5. Principle of piezoelectric pressure sensor

The main piezoelectric materials used in piezoelectric sensors include quartz, potassium sodium tartrate and ammonium dihydrogen phosphate. Among them, quartz (silicon dioxide) is a natural crystal. The piezoelectric effect is found in this crystal. Within a certain temperature range, the piezoelectric properties always exist, but after the temperature exceeds this range, the piezoelectric properties are completely lost. disappears (this high temperature is the so-called "Curie point"). Since 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.