RU2670244C1 - Pressure sensor - Google Patents

Abstract

FIELD: instrument engineering.SUBSTANCE: invention relates to instrumentation, namely to pressure sensors, the sensitive elements of which are a tensor-transducer having in its composition a plate with strain gauges, connected to the measuring bridge, and a membrane unit that senses the measured pressure. In the design of the sensor, an elastic element is used that carries out the connection of the membrane unit to the strain gauge. Elastic element is a spring or bellows. Membrane unit is made in the form of two identical interconnected membranes, one of which is fixed in the sensor housing and the other has a rigid center that senses the pressure. Under the influence of the load on the membrane unit, force is transferred through the elastic element (spring or bellows) to the strain-gauge plate. Movement of the membrane unit continues to the end of its rigid center in the body of the strain gauge. With a further increase in the load, the movement of the membrane block does not take place and the force on the plate of the strain gauge is not transmitted. Introduction of the connection between the membrane unit and the plate of the tensor-transducer through an elastic element allows to protect the strain-gauge from impact loads and ensure that the required output signal is obtained at a ratio of the stiffnesses of the membrane unit, the elastic element and the tensor plate for each measurement range.EFFECT: ensuring the possibility of using in static and dynamic overload conditions, increasing the reliability of the sensor and the possibility to increase the sensitivity of the sensor in the lower measurement range.4 cl, 3 dwg

Description

The present invention relates to instrumentation, namely to pressure sensors.

Known absolute and gauge pressure sensors, for example of the type "Sapphire-22", using the strain gauge measurement method [1].

The pressure sensor has a metal case, inside which a strain gauge is placed, and a membrane unit, and on the outside of the case is an electronic device. The strain gauge and the membrane unit are sensitive elements of the pressure sensor. The strain gauge has a single crystal sapphire plate with silicon film strain gauges connected in the form of a measuring bridge. The membrane block is a corrugated metal membrane welded along the outer contour to the sensor housing.

The diaphragm block senses the measured pressure and transfers mechanical stresses to the strain gauge.

An organosilicon liquid located in a volume closed between the strain gauge and the membrane block performs practically rigid transfer of mechanical stresses from the membrane block to the strain gauge.

The figure 1 shows a structural diagram of a known pressure sensor [1].

The principle of operation of the known sensor is as follows. The measured pressure P acts on the corrugated metal membrane 1 and through the liquid 2 on the plate 3 with strain gauges connected to the measuring bridge. Under the action of mechanical stresses arising in the plate 3, the resistance of the strain gages in the shoulders of the bridge changes and an unbalance voltage appears at the output of the bridge circuit, which is converted into an output electrical signal proportional to the input load. The electrical signal from the strain gauge is transmitted to the electronic device 4.

The low reliability of the known pressure sensors is caused by the rigidity of the transmission of mechanical stresses from the membrane unit to the strain gauge. In the measured object, hydrodynamic shocks and pressure vibrations are possible, which, due to the stiffness of the transmission, are directly perceived by the strain gauge plate and contribute to its destruction.

There is also a vulnerability of the strain gauge plate to exceeding the input load value with respect to the upper limit of measurements, to static pressure overloads, and restrictions are created on the lower sensitivity threshold.

The sensor, made according to the alleged invention, is protected from static and dynamic overloads, and it is also possible to increase sensitivity in the lower measurement range. To ensure this, an elastic element is used in the sensor design that connects the membrane unit to the strain gauge. It is proposed to use a spring or a bellows as an elastic element. In addition, the membrane unit is made in the form of two identical interconnected membranes, one of which is fixed in the sensor housing, and the other has a rigid center that receives pressure.

The figure 2 shows a structural diagram of a sensor made according to the alleged invention, with an elastic element in the form of a spring. The membrane unit 1 is connected to the plate 3 of the strain gauge along the load axis through an elastic element 2 (spring), mounted on the rigid centers of the plate 3 and the membrane unit 1.

The figure 3 shows a structural diagram of a sensor made according to the alleged invention, with an elastic element in the form of a bellows. The membrane unit 1 is connected to the plate 3 of the strain gauge along the load axis through an elastic element 2 (bellows), mounted on the rigid centers of the plate 3 and the membrane unit 1.

When applying pressure P to the membrane unit 1, the transfer of force to the plate 3 of the strain transducer occurs through an elastic element 2 (spring or bellows). Under the action of the load, the movement of the membrane unit 1 continues until the stop of its rigid center 4 in the housing part 5 of the strain gauge, rigidly fixed in the housing of the pressure sensor. With a further increase in the load, movement of the rigid center 4 of the membrane unit 1 does not occur, as a result of which the force is not transmitted to the plate 3.

The introduction of the connection of the membrane unit 1 and the plate 3 through the elastic element 2 allows you to protect the plate 3 of the strain transducer from vibration and shock loads, and to provide the necessary output signal with the ratio of the stiffnesses of the membrane unit 1, the elastic element 2 and plate 3 for each measurement range.

Using one version of the strain gauge with an elastic element (spring or bellows) in the pressure sensors, and using membrane blocks of various sizes and stiffness, it is possible to provide pressure measurement in the ranges from 6.3⋅10 ^-3 to 4 MPa.

A positive technical result from the application of the proposed invention is:

- improving the reliability of pressure sensors;

- the possibility of using pressure sensors in working conditions with the probability of shock loads and during static pressure overloads;

- the possibility of increasing the sensitivity of pressure sensors due to the use of membrane blocks of various sizes and stiffnesses.

INFORMATION SOURCES

1 Measuring converter "Sapphire-22". Technical description and instruction manual. 08919030 TO.

Ministry of Instrument Engineering, Automation and Control Systems, Moscow, 1983

Claims (4)

1. A pressure sensor comprising a housing with a strain gauge located inside, the sensitive element of which is a plate with strain gauges connected to a measuring bridge, and a membrane unit that receives pressure and contains at least one membrane, characterized in that the connection between the membrane unit and the sensitive element of the strain gauge is made in the form of an elastic element. 2. The pressure sensor according to claim 1, characterized in that a spring is used as the elastic element. 3. The pressure sensor according to claim 1, characterized in that a bellows is used as the elastic element. 4. The pressure sensor according to claim 1, characterized in that the membrane unit is made of two identical interconnected membranes, one of which is fixed in the housing, and the other has a rigid center that receives pressure.

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