1、Piezoelectric pressure sensors.

Pressure sensor principle: the principle of the situation formed mainly due to the generation of the piezoelectric effect. The main piezoelectric materials used in pressure sensors include quartz, potassium sodium tartrate and dihydrogen phosphate amine. Quartz|silica is a natural crystal in which the piezoelectric effect is found. The piezoelectric properties are present up to a certain temperature range, but disappear completely when the temperature exceeds this range. The high temperature is the so-called Curie point. Due to the small change in electric field with stress, i.e. the low piezoelectric coefficient, quartz was gradually replaced by other piezoelectric crystals. The piezoelectric effect is applied to polycrystals such as piezoelectric ceramics, including barium titanate piezoelectric ceramics, PZT, niobate series piezoelectric ceramics, lead niobium-magnesate piezoelectric ceramics, etc.

Applications:Pressure sensors are mainly used in the measurement of acceleration, pressure and force. The pressure sensor is a commonly used accelerometer. It has excellent features such as simple structure, small size, light weight and long service life. Pressure transducers have found a wide range of applications in vibration and shock measurements in aircraft, automobiles, ships, bridges and buildings and have a special place in aviation and astronautics in particular. Pressure sensors can also be used for the measurement of combustion pressure inside engines and for the measurement of vacuum levels. Pressure sensors are also used in the military industry, for example to measure the change in bore pressure at the moment of firing of a gun cartridge in the chamber and the shock wave pressure at the muzzle of a gun. It can be used to measure both large and small pressures. Pressure sensors are also widely used in biomedical measurements, for example ventricular catheterised microphones are made from piezoelectric sensors, because measuring dynamic pressure is so common. Pressure sensors cannot be used for static measurements because the charge after an external force is only conserved if the circuit has an infinite input impedance. This is not the case in practice, so this determines that piezoelectric sensors can only measure dynamic stresses.

2. Strain gauge pressure sensors:

Principle of pressure sensors:Because of the widespread use of piezoresistive pressure sensors, their metal resistance strain gauges work by adsorbing strain resistance on the substrate material to produce a change in resistance with mechanical deformation, commonly known as the resistive strain effect. The strain gauge is a sensitive device that converts the strain change on the measured part into an electrical signal. It is one of the main components of piezoresistive strain sensors.

The two most used types of resistive strain gauges are metal resistance strain gauges and semiconductor strain gauges. There are two types of metal strain gauges: wire strain gauges and metal foil strain gauges. The strain gauges are usually bonded tightly to a mechanical strain-generating substrate by means of a special adhesive. When the substrate is subjected to stress changes, the strain gauges are deformed together, resulting in a change in the resistance of the strain gauges and thus in the voltage applied to the resistance. These strain gauges, which usually produce a small change in resistance when subjected to stress, are generally formed into strain bridges and amplified by subsequent instrumentation amplifiers, which are then transmitted to the processing circuit (usually A/D conversion and CPU) for display or actuation.

The internal structure of a metal resistance strain gauge: The resistance strain gauge consists of the base material, the metal strain wire or strain foil, the insulating protection sheet and the lead wire. Depending on the application, the resistance value of the strain gauge can be designed by the designer, but the range of resistance values should be noted: too small a resistance value will require too much driving current, while the heating of the strain gauge will cause the temperature of the gauge itself to be too high, and the use of the gauge in different environments will cause the resistance value of the gauge to change too much, the output zero point will drift significantly, and the zero adjustment circuit will be too complicated. The resistance is too large and the impedance is too high, making it less resistant to external electromagnetic interference. Generally are a few dozen to a few dozen kilo-ohm or so.

3, ceramic pressure sensor.

Pressure sensor principle: the pressure acts directly on the front surface of the ceramic diaphragm, so that the diaphragm produces a small deformation, thick film resistor printed on the back of the ceramic diaphragm, connected into a Wheatstone bridge (closed bridge), due to the piezoresistive effect of the piezoresistor, so that the bridge produces a highly linear proportional to the pressure, and the excitation voltage is also proportional to the voltage signal, the standard signal according to the pressure range of different calibrations for The standard signals are calibrated to 2.0/3.0/3.3mV/V etc. depending on the pressure range and are compatible with strain gauge sensors. With laser calibration, the pressure sensors have a high temperature and time stability, the sensors come with temperature compensation from 0 to 70°C and can be in direct contact with most media.

Pressure sensor applications:Ceramics is a recognised material that is highly elastic, resistant to corrosion, wear, shock and vibration. The thermally stable properties of ceramic and its thick film resistance can enable it to operate over a temperature range of up to -40~135°C and with high accuracy and stability of measurement. Electrical insulation degree of 2kV, strong output signal and good long-term stability. High characteristics, low price of ceramic sensors will be the direction of development of pressure sensors, in Europe and the United States has a comprehensive replacement for other types of sensors, in China, more and more users are also using ceramic sensors to replace the diffusion of silicon pressure sensors.

4, sapphire pressure sensor

Pressure sensor principle: the use of strain resistance type work, the use of silicon - sapphire as a semiconductor sensitive components, with unparalleled measurement characteristics. The circuitry of the pressure sensor ensures that the strain bridge circuit is powered and that the out-of-balance signal from the strain bridge is converted into a uniform electrical output. In adiabatic pressure sensors and transmitters, thin sapphire sheets, joined together with ceramic base glass solder, act as an elastic element that converts the measured pressure into strain gauge deformation for the purpose of pressure measurement.

Future industry pressure sensor application distribution trends

In the medical equipment, special equipment mainly includes medical, environmental protection, meteorological and other fields of application of professional electronic equipment. The medical field is currently an emerging market for pressure sensors with huge sales volume and considerable profits.

Automotive electronics industry, the key to the level of electronic control system of modern senior cars lies in the number and level of pressure sensors used, currently an ordinary family car installed on about dozens to nearly a hundred sensors, and the requirement of sensor parts to miniaturization, low cost and high reliability direction.

In communications, the significant growth in mobile phone production and mobile phone new features continue to increase to the sensor market opportunities and challenges, color screen mobile phones and camera phones rising market share increased the proportion of sensors in the field of application. In addition, ultrasonic sensors used in group phones and cordless phones, magnetic field sensors for magnetic storage media, etc. will see strong growth.

These are the areas where sensors are most used and pressure sensors are mainly sold in these industries, but with the development of sensors, many industries are also actively developing the use of sensors, such as some consumer industries, such as running sensors on shoes and pulse sensors on wrist guards. Many new types of sensors are being widely opened up for use.