Pressure sensor type and principle analysis
Sensor technology is one of the symbols of the development level of modern science and technology, and pressure sensor technology is an important branch of sensor technology. At present, various types of pressure sensors, such as diffusion silicon, capacitive, silicon sapphire, ceramic thick film, and metal strain electrical type, are widely used in various industries of national production and science and technology. The following briefly describes the characteristics of some commonly used pressure sensors and the differences between them.
Sapphire pressure sensor
The sapphire pressure sensor uses strain-resistance working principle and uses silicon-sapphire as a semiconductor sensing element, which has unparalleled metering characteristics.
Sapphire is composed of single-crystal insulator elements that do not suffer from hysteresis, fatigue, and creep; sapphire is stronger and harder than silicon, and is not afraid of deformation; and sapphire has excellent elasticity and insulation, so it is made of silicon-sapphire. The semiconductor sensing elements are insensitive to temperature changes and have good operating characteristics even under high temperature conditions; sapphire has extremely strong radiation resistance characteristics; in addition, silicon-sapphire semiconductor sensitive elements do not have pn drift, so they are fundamentally simplified. The manufacturing process improves repeatability and ensures high yields.
Pressure sensors and transmitters manufactured with silicon-sapphire semiconductor sensing elements can operate normally under the harshest operating conditions, and have high reliability, accuracy, minimal temperature error, and cost-effectiveness.
Diffused silicon pressure sensor
The operating principle of the diffusion silicon pressure sensor is that the pressure of the measured medium directly acts on the diaphragm (stainless steel or ceramic) of the sensor, so that the diaphragm generates a micro displacement proportional to the pressure of the medium, so that the resistance value of the sensor changes. The electronic circuit detects this change and converts a standard measurement signal corresponding to this pressure.
Ceramic pressure sensor
Corrosion-resistant ceramic pressure sensors do not transfer liquid. The pressure acts directly on the front surface of the ceramic diaphragm and the surface of the chamber diaphragm, causing a slight deformation of the diaphragm. The thick film resistor is printed on the back of the ceramic diaphragm and is connected to a Wheatstone bridge (closed bridge), due to the piezoresistive effect of the varistor, causes the bridge to produce a highly linear voltage proportional to the pressure and a voltage signal proportional to the excitation voltage. The standard signal is scaled according to the difference in pressure range. 2.0, 3.0, 3.3mV, etc., compatible with strain gauge sensors. Through laser calibration, the sensor has a high temperature stability and time stability, the sensor comes with a temperature compensation of 0 °C ~ 70 °C, and can be in direct contact with most of the media.
Ceramics is a well-known material with high elasticity, corrosion resistance, wear resistance, impact resistance and vibration. The thermal stability of the ceramic and its thick film resistance can make its operating temperature range up to -40°C~135°C, and it has high precision and high stability of measurement. Electrical insulation greater than 2KV, strong output signal, good long-term stability. High-performance, low-cost ceramic sensors will be the development direction of pressure sensors. In Europe and the United States, there is a trend to completely replace other types of sensors. In China, more and more users use ceramic sensors instead of diffusion silicon pressure sensors.