The pressure sensor is a common sensor in industry, and is widely used in various industrial control environments, including hydropower, production automation, petrochemical, machine tools and other industries, so the pressure sensor is a very practical sensor. The types of pressure transmitters are roughly the following: resistance strain gauge pressure transmitters, semiconductor strain gauge pressure transmitters, piezoresistive pressure transmitters, inductive pressure transmitters, capacitive pressure transmitters, Resonant pressure transmitters and capacitive acceleration sensors. But the most widely used is the piezoresistive pressure transmitter, which has a very low price, high accuracy and good linearity. Below we mainly introduce this type of transmitter.
Ceramic pressure transmitter
Ceramics is a well-known material with high elasticity, corrosion resistance, wear resistance, impact resistance and vibration. The thermal stability of ceramics and its thick film resistance can make its operating temperature range up to -40 ~ 135 °C, but also has high precision and high stability. Electrical insulation >2kV, strong output signal, good long-term stability. High-performance, low-cost ceramic sensors will be the development direction of pressure transmitters.
Diffused silicon pressure transmitter
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, and the change is detected by the electronic circuit, and The conversion outputs a standard measurement signal that corresponds to this pressure.
Piezoelectric pressure transmitter
Piezoelectric materials mainly used in piezoelectric sensors include quartz, sodium potassium tartrate, and diammonium phosphate. Among them, quartz (silicon dioxide) is a kind of natural crystal. The piezoelectric effect is found in this kind of crystal. Within a certain temperature range, the piezoelectricity is always there, but after the temperature exceeds this range, the piezoelectricity is completely Disappear (this high temperature is the so-called "curie point"). Because the electric field changes little with the change of stress (that is, the piezoelectric coefficient is relatively low), quartz is gradually replaced by other piezoelectric crystals. Potassium sodium tartrate has a large piezoelectric sensitivity and piezoelectric coefficient, but it can only be applied in environments with low room temperature and low humidity. Dihydrogen phosphate is an artificial crystal that can withstand high temperatures and high humidity, so it has been widely used. Now the piezoelectric effect is also applied to polycrystals, such as current piezoelectric ceramics, including barium titanate piezoelectric ceramics, PZT, niobate piezoelectric ceramics, lead magnesium niobate piezoelectric ceramics, and the like.
Capacitive pressure transmitter
Ceramic capacitive sensors have measurements suitable for normal or corrosive media, such as gases, gases or liquids, but do not tend to precipitate, crystallize or stiffen materials as recommended. Used for cabin level measurement, sea water, water on board, diesel oil, waste oil.
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