RU2360221C2 - Pressure sensor - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: proposed pressure sensor has a case which houses a detecting element with a measuring plate, heat-producing element, connected to a slip connector, and a screen. An opening is made in the case for communication with the atmosphere, which goes into a threaded joint of the case with the detecting element. The screen is electrically connected to the case, rests on it and is fixed in it along the perimetre such that, it is divided into two insulated cavities. The heat-producing element is installed in the upper cavity on the screen, and the measuring plate with the detecting element is installed in the lower cavity. Along the perimetre, the screen has lugs, with which it is fixed in the case.

EFFECT: increased accuracy of measurement, reduced time of setting up the required output signal and simple design.

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Description

The invention relates to measuring equipment, namely to small-sized pressure sensors, and can be used in metering systems, automatic control and regulation of industrial processes, etc.

Known pressure sensors CJSC "Research and Production Complex" VIL "(Product Catalog, Yekaterinburg, 2004, p.4-11) and small-sized pressure sensors" Metran-55 "of the Industrial Group" Metran "(Thematic catalog No. 1, issue 2, p.128-131). Each sensor contains a strain gauge located in a common cavity of the housing with a measuring board and a fuel element. The electrical circuit located on the measuring board is a fuel element.

All thermal and electromagnetic effects from the heat source and sensor connection circuits propagate in one of its cavities. In addition, the heat source is located near the measuring board and the sensing element of the strain gauge. All this increases the error of the sensor, reduces the accuracy of the measurement.

A known sensor according to Russian patent No. 2261419, G01L 9/00, comprising a sensing element located in a common cavity of the housing with a measuring board and a fuel element that is connected to the plug block and is made in the form of a hybrid integrated circuit integrated into the measuring board. A hybrid integrated circuit is glued to the sensor.

All thermal and electromagnetic effects from the heat source and sensor connection circuits propagate in one of its cavities. In addition, the heat source is located near the measuring board and the sensing element, which changes their electrical parameters, increasing the error of the sensor.

When the measuring board is in direct contact with the pressure contacts and plug-in contacts, the induced electromagnetic pulses in the elements of the measuring board adversely affect the conversion function of the hybrid integrated circuit and other connection circuits. This impairs magnetic compatibility, increasing the accuracy of the sensor.

Using the pressure contacts, mechanical forces are transmitted directly to the metal sleeve and the sensitive membrane through the contact points. This creates uneven mechanical effects that increase the accuracy of the sensor. The force transmitted by the spring contacts to the sensitive membrane has an additional dependence on the ambient temperature, which increases the error of the sensor.

During the adhesive contact of the hybrid integrated circuit with the sensitive element, mechanical stresses arise due to the mismatch of the temperature expansion coefficients of various contacting materials, which also increases the error of the sensor.

All this reduces the accuracy of the measurement.

In addition, all these thermal and mechanical effects increase the transient time associated with setting the required output signal after the sensor is turned on and after each pressure change.

Also known is an overpressure sensor MIDA-DI-13P CJSC Microelectronic Sensors and Devices (Technical Description and Operating Instructions, TNKI. 406233.033 TO, 2002, p.6-7, Fig.1a), adopted as a prototype and containing a sensing element located in a common cavity of the housing with a measuring board and a fuel element that is connected to the plug block. The electrical circuit located on the measuring board is a fuel element. A hole is made in the upper part of the housing, which extends into the cavity of the housing to communicate with the atmosphere. A filter is installed in the hole, and a cap is put on top of the case to protect the body cavity from dust and moisture.

Since the pressure-sensitive element is located in the immediate vicinity of the fuel element, it heats up and expands, perceiving mechanical stresses that create slowly relaxing stresses and deformations of the elements. This changes their electrical parameters, increasing the accuracy of the sensor.

In addition, all these thermal and mechanical effects increase the transient time associated with setting the required output signal after the sensor is turned on and after each pressure change. Since pressure changes in the systems under study can usually occur frequently, it turns out that most of the time a sensor is used that does not provide the declared accuracy class, which reduces the measurement accuracy to 0.5%.

The hole in the housing, which goes directly into its cavity, is through. It communicates with the atmosphere the cavity of the sensor, but to ensure reliable operation, it is necessary to protect the internal elements of the sensor from moisture and dust that can penetrate into the open hole. To do this, a filter and a protective cap are installed, which complicate and increase the cost of construction.

The objective of the invention is to increase the accuracy of measurement, reducing the installation time of the desired output signal and simplifying the design.

The pressure sensor contains a sensing element located in the housing with a measuring board and a fuel element associated with the plug block, an opening is made in the housing for communication with the atmosphere.

Unlike the prototype, it contains a screen that is electrically connected to the body, abuts against it and fixed in it around the perimeter in such a way that it divides into two isolated cavities. A fuel element is installed on the screen in the upper cavity, and a measuring board with a sensitive element is installed in the lower cavity.

The perimeter screen is made with elastic petals, with the help of which it is fixed in the housing.

The hole in the housing for communication with the atmosphere of the lower cavity of the sensor goes into the threaded connection of the housing with the sensing element.

Since the screen corresponds in shape to the internal section of the housing, abuts against it and is fixed in it around the perimeter, the screen divides the housing into two isolated cavities, which makes it possible to separate and maximize the removal of the fuel element from the sensing element with the measuring board. This reduces the thermal and electromagnetic effects on the sensing element and the measuring board, reducing the error of the sensor.

As a result, all this increases the measurement accuracy by 0.3%.

Reducing the effect of thermal and electromagnetic influences on the sensor element and the measuring board reduces the transient time associated with setting the required output signal after the sensor is turned on and after each pressure change.

The implementation of the screen with curved elastic petals located along its perimeter, facilitates its fastening to the housing.

The hole in the housing opposite the threaded connection provides a connection of the sensor cavity with the atmosphere. However, the edges of the hole abut against a thread that overlaps it, protecting it from moisture and dust. Tests showed that the threaded connection allows air to enter the body cavity, but does not allow moisture and dust to pass through, as they cannot overcome a long circular path along the threads. This eliminates the need to install the filter in the hole and protect it with a cap, which simplifies and reduces the cost of construction.

Thus, all the signs are significant and solve the problem.

The invention is presented in the drawings.

Figure 1. Pressure meter. General view in section.

Figure 2. Screen. Top view, enlarged, petals unbent.

The pressure sensor includes a housing 1, in which a metal screen 2 is rigidly fixed around the perimeter, dividing it into two isolated cavities: the lower 3 and the upper 4. A sensing element 5 is installed in the lower cavity 3, for example, a strain gauge, to the collectors 6 of which a measuring board 7 is fixed. A hole 8 is made in the housing 1 for communicating the cavity of the sensor 3 with the atmosphere. In the upper cavity 4 on the screen 2, a fuel element 9 is installed, for example, a powerful transistor connected electrically to the plug block 10. It is possible to fix the transistor 9 to an auxiliary PCB board 11 and then install it on the screen 2, Fig. 1.

The screen 2 is installed in the housing 1, providing its contact with the inner wall of the housing using elastic petals 12, figure 1, figure 2. The petals 12 are fixed in the housing 1 around the perimeter, for example, with heat-conducting adhesive. Thus, in the housing 1, two cavities 3 and 4 are isolated from each other.

As a result, screen 2 performs several functions:

- a body divider into two isolated cavities;

- shielding (isolation) of the strain gauge and the measuring board from electromagnetic and thermal effects of the transistor and sensor connection circuits;

- ensuring electrical connection of the housing to the measuring board;

- holder for the transistor.

The most optimal is the execution in the housing 1 of the hole 8 opposite the middle of the length of the threaded connection 13 of the housing 1 with the strain transducer 5.

Claims (3)

1. A pressure sensor comprising a sensing element located in the housing with a measuring board and a fuel element connected to the plug connector, a hole is made in the housing for communication with the atmosphere, characterized in that it further comprises a screen electrically connected to the housing and fixed in it by the perimeter in such a way that it divides into two isolated cavities, a fuel element is installed on the screen in the upper cavity, and a measuring board and a sensing element are installed in the lower cavity. 2. The pressure sensor according to claim 1, characterized in that around the perimeter of the screen there are elastic petals with which it is fixed in the housing. 3. The pressure sensor according to claim 1, characterized in that the hole in the housing for communication with the atmosphere of the lower cavity of the sensor goes into the threaded connection of the housing with the sensing element.

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