Pressure sensor is a kind of sensor that is widely used in sensors. It is generally used to measure large pressure. It is widely used to measure the internal pressure of pipelines, the pressure of internal combustion engine gas, differential pressure and injection pressure, the pulsating pressure in engine and missile tests, as well as the fluid pressure in various fields.
There are also many types of pressure sensors, mainly including the following:
1. Diaphragm type
Its elastic sensing element is a circular metal flat diaphragm fixed around it. When the diaphragm is deformed by pressure, the radial strain and tangential strain at the center reach a positive maximum, while the radial strain at the edge reaches a negative maximum, and the tangential strain is zero. Therefore, two strain gauges are often attached to the positive and negative maximum strains respectively, and connected into a half bridge circuit of adjacent bridge arms to obtain greater sensitivity and temperature compensation. Using a circular foil strain gauge (see resistance strain gauge) can maximize the strain effect of the diaphragm.
The nonlinearity of this kind of sensor is remarkable. The latest product of the diaphragm pressure sensor is a solid-state pressure sensor (see piezoresistive sensor) that integrates the functions of elastic sensing elements and strain gauges into a monocrystalline silicon diaphragm, that is, a resistance bar is diffused on the monocrystalline silicon diaphragm by using the integrated circuit process, and the peripheral fixed structure is used.
2. The strain tube type is also known as the strain tube type.
Its elastic sensing element is a thin-walled cylinder with one end closed, and the other end is connected with the tested system with a flange. Two or four strain gauges are pasted on the cylinder wall, half of which are pasted on the solid part as temperature compensation gauges, and the other half as measuring strain gauges. When there is no pressure, four strain gauges form a balanced full bridge circuit; When the pressure acts on the inner cavity, the cylinder deforms into a waist drum shape, which makes the bridge out of balance and outputs a voltage that is related to the pressure. The sensor can also use the piston to convert the measured pressure into force and transfer it to the strain cylinder or transfer the measured pressure through the diaphragm in the shape of a vertical chain.
The strain tube pressure sensor has the advantages of simple structure, convenient manufacture and strong applicability. It is widely used in the dynamic pressure measurement of rockets, shells and artillery.
3. Combined type
In the combined strain pressure sensor, the elastic sensing element can be divided into sensing element and elastic strain element. The sensing element converts pressure into force and transmits it to the most sensitive part of the elastic strain element, and the strain gauge is attached to the maximum strain of the elastic strain element. In fact, the more complex strain tube type and strain beam type belong to this type. Sensing elements include diaphragm, capsule, bellows, Bourdon tube, etc., and elastic strain elements include cantilever beam, fixed beam, shaped beam, annular beam, thin-walled tube, etc. They can be combined into various types according to different needs. The pressure sensor is mainly used to measure the dynamic or static pressure of flowing medium, such as the pressure of gas or liquid at the inlet and outlet of power pipeline equipment, the pressure of internal combustion engine pipeline, etc.
4. Strain beam type
When measuring small pressure, the structure of fixed beam or equal strength beam can be used. One method is to use the diaphragm to convert the pressure into force, and then transfer it to the strain beam through the dowel rod. The maximum strain of the fixed beam at both ends is at both ends and the midpoint of the beam, and the strain gauge is pasted at these places. There are other forms of this structure, such as suspension beams and diaphragms or bellows.
Post time: Jul-02-2022