RU45526U1 - PRESSURE METER - Google Patents

Abstract

The utility model relates to the field of instrumentation, namely to strain gauge devices for measuring pressure, and can be used mainly in converters of pressure, vacuum, pressure difference, flow rate and level of liquid and gaseous media into an electrical signal.

The goal is to increase sensitivity, minimize overall dimensions, reduce the consumption of expensive materials, improve the manufacturability of the design.

The device contains a membrane and a strain gauge element. The membrane contains an outer thick annular bezel, a thin annular part, perceiving pressure, and a thick rigid center. A strain-sensitive element is rigidly fixed to the membrane’s flat surface, which is a rectangular dielectric substrate having a length to width ratio of at least 3: 1, located symmetrically relative to the center of the membrane and covering no more than 30% of the outer surface of the membrane, whose strain-sensitive resistors are located on the surface of the dielectric substrates in the transition zones from the thin part to the thick part, both in the zone of the outer ring and in the zone of the rigid center, and all have the same op entatsiyu or only along the long side, or only perpendicular to it. In addition, the receiving membrane with its lower part can be welded to the housing of various shapes, for example, cylindrical with additional cutouts, grooves and threads, to ensure installation in various measuring devices. In addition, on the receiving membrane on a rigid outer ring from the side of the strain-sensing element can be fixed through a metal sleeve or directly to a dielectric collector with metal contacts, and a dielectric cover can be mounted on it.

The device provides high strain sensitivity and accuracy in a single-membrane design with small overall dimensions, a small change in the output signal with a change in temperature, long-term stability and reliability in a wide temperature range and is characterized by

compactness, manufacturability, low consumption of expensive materials. 6 p. Fs, 5 ill.

Description

The utility model relates to the field of instrumentation, namely to strain gauge devices for measuring pressure, and can be used mainly in converters of pressure, vacuum, pressure difference, flow rate and level of liquid and gaseous media into an electrical signal.

A device for measuring pressure, described in A.S. USSR No. SU 1719940 according to class G 01 L 9/04.

The known device contains a sapphire substrate of square shape, rigidly connected to a metal membrane, machined at the same time with the body, and covering almost all of the upper surface of the membrane. On the surface of the substrate near the membrane contour there are silicon strain gages oriented in parallel (two resistors) and perpendicular (also two resistors) to the radius of the membrane and connected to a bridge circuit.

The disadvantage of this device is its low sensitivity to the measured pressure, which allows it to be used to measure pressures of more than 4 MPa.

The closest in technical essence to the proposed and adopted as a prototype is a pressure transducer type D16, described in the article - Perepelitsyn O.P., Blagodetelev S.V., Design and technical characteristics of strain transducers based on silicon-sapphire structures, Sensors and systems, 2002, special issue to No. 10.

The known pressure-sensitive device is a structure consisting of a housing and measuring membranes rigidly connected to each other by a welded joint. On the upper surface of the measuring membrane, a square-shaped dielectric substrate made of a single-crystal material with silicon strain gauges is rigidly fixed, covering almost completely the upper surface of the membrane. The upper measuring membrane has a thin part and a rigid center. The measured pressure acts on the membrane, deforming both the membrane and the dielectric substrate with

strain gages.

The disadvantages of the prototype include the significant rigidity of the measuring membrane with a dielectric substrate attached to it with silicon strain gages, which has an elastic modulus of 3-4 higher than the membrane material, and also has technological limitations on reducing its thickness, which does not significantly increase the sensitivity, by reducing the thickness of the membrane. An increase in diameter leads to an increase in the area of an expensive crystal, the overall dimensions of the sensors in which a device for measuring pressure is used, which in some cases is unacceptable. In addition, there are technological difficulties and limitations in the manufacture of large-diameter membranes having a unitary design with a thick edge rim that compensates for parasitic deformations during fastening, with a thin part of a large area and a thick rigid center. These disadvantages of the prototype do not allow it to be used in highly sensitive small-sized industrial measuring transducers of pressure, vacuum, pressure difference, flow rate and level of liquid and gaseous media into an electrical signal.

The purpose of the claimed utility model is to significantly increase the sensitivity of the device for measuring pressure based on the strain effect, minimize overall dimensions, reduce the consumption of expensive materials and improve the manufacturability of the design.

This goal is achieved by the fact that in a pressure measuring device containing a membrane having a thick outer ring, a thin part in the form of a ring, a thick rigid center, and at least two strain gages placed on a dielectric substrate rigidly fixed to the upper surface of the membrane, near areas of transitions of a thin part into a thick one, according to a utility model, an elongated rectangular dielectric substrate with a side ratio of at least 3: 1 and covering the four part of the membrane area, and on the dielectric substrate, on the upper surface of the measuring membrane, in the four regions of transition of the thin part to the thick part, four strain-sensitive resistors are placed near the outer ring and near the rigid center, which have the same orientation along the long side of the membrane or perpendicular to it and connected in

bridge or other circuit.

In addition, the lower side of the membrane can be rigidly connected along an external rigid ring with a housing of various shapes.

In addition, an insensitive to deformation and temperature-sensitive resistor made of heteroepitaxial silicon or other material can additionally be placed on the dielectric substrate.

In addition, a transition ring can be rigidly fixed to the outer thick membrane ring.

In addition, a collector made of dielectric material with metallized conductors can be rigidly fixed to the adapter ring.

In addition, a cap of dielectric material may be rigidly fixed to the collector.

Due to the fact that the dielectric substrate has an elongated rectangular shape, having an aspect ratio of at least 3: 1, and covers only a smaller part of the membrane area, the membrane stiffness is reduced 1.5–2 times, since the elastic modulus of the dielectric substrate (leucosapphire) is 3 -4 times higher than the modulus of elasticity of the membrane (titanium alloy), and thus the sensitivity of the device to the measured pressure is increased 1.5-2 times, and due to the placement of four strain gages located in the positive zones on the dielectric substrate deformation (near the rigid center) and negative deformation (near the outer ring) under the influence of the measured pressure, connected in a bridge circuit and oriented equally along or perpendicular to the long side, high pressure sensitivity and low temperature sensitivity are achieved, since when exposed to temperature all strain gages are either compressed or stretched to the same degree, automatically compensating for the change in the output signal.

An additional advantage of the device is a 2-3-fold reduction in the consumption of an expensive dielectric substrate with a layer of a strain-sensitive semiconductor material deposited on it, for example, silicon-on-sapphire, as well as an improvement in manufacturability, which eliminates two welded joints due to the absence of a second membrane .

The inventive device for measuring pressure has a novelty in comparison

with the prototype, differing from it by such significant features as a rectangular shape of the dielectric substrate with an aspect ratio of 3: 1 or more, which covers a smaller part of the membrane area, the use of four longitudinal strain gages placed on the dielectric substrate in the transition zone of the thin part to the thick one near the hard center and near the outer thick ring, and oriented equally along the long side of the rectangular measuring membrane or perpendicular to it and connected to a bridge circuit or another scheme, which together provide a high sensitivity of the device to the measured pressure and low parasitic influence of temperature.

The inventive device for measuring pressure can be widely used in measuring technology and therefore meets the criterion of "industrial applicability".

The inventive utility model is illustrated by drawings, which are presented on:

- figure 1 - device for measuring pressure - top view;

- figure 2 is a section aa from the side of the end;

- figure 3 - option 1 of the device for measuring pressure is a section along the axis;

- figure 4 is an embodiment 2 of a device for measuring pressure.

The pressure measuring device (FIG. 1, FIG. 2) comprises a measuring membrane 1 and a dielectric substrate 2, while the measuring membrane 1 consists of an external thick ring, a thin part of the membrane 3 and a thick rigid center 4, and the dielectric substrate contains strain gauges 5 and 6, equally oriented and located near the transition zones of the thick part to the thin part, which are the zones of greatest deformation under pressure. Strain gages 5 are placed in zones with a positive strain sign, and strain gages 6 in zones with a negative strain sign under pressure, which, with the same orientation, leads to a change in resistances with different signs, providing an imbalance of the bridge circuit. The unitary construction of the measuring membrane 1 is made of an elastic alloy, for example, of a titanium alloy.

The dielectric substrate 2 has a rectangular shape with an aspect ratio

3: 1 or more and is made, for example, from a plate of artificial leucosapphire with a certain crystallographic orientation, for example (1012), on the surface of which a silicon layer is grown, from which strain gages 5 and 6 are formed, oriented along the crystallographic directions (011) of silicon, and possibly insensitive to deformation and temperature-sensitive resistor 7, oriented in the direction of minimum strain sensitivity, for example, at 45 ° to the crystallographic direction (011) of silicon. The sapphire substrate 2 can be mounted on the surface of the titanium alloy measuring membrane 1 by high-temperature brazing with silver-containing solder, for example, ПСР-72, while a high limit of plastic deformation and a small thickness of the solder layer provide high metrological characteristics of the device.

Figure 3 shows an embodiment of a device for measuring pressure, further comprising a housing 8, which may have threads and various chamfers and cutouts.

Figure 4 shows an embodiment of a pressure measuring device in which, in addition to the previous embodiment, there is a metal sleeve 9 and a collector 10 made of dielectric material with metal contacts. The sleeve 9, for example, of a titanium alloy, is connected to the measuring membrane 1 by laser or argon-arc welding. The collector is connected to a sleeve, such as glue. Silicon strain gauges connected to the bridge circuit are connected by thin conductors, for example, gold or aluminum, to the metal contacts of the collector. In addition, with the help of glue or in another way, a cap 11 made of dielectric material can be fixed to the collector, which covers the measuring membrane and the dielectric substrate with silicon strain gauges from external influences.

A device for measuring pressure operates as follows.

The measured pressure is applied to the membrane 1 in the direction of the dielectric substrate 2, causing a deflection of the membrane 1 and the dielectric substrate 2, proportional to the applied pressure. In this case, under the influence of deformation, the strain gauges 5 and 6 included in the bridge or differential measuring circuit (not shown) will change their initial resistance, and the strain gauges

5 (FIG. 1) increase, and strain gages 6 (FIG. 1) reduce their resistance, as a result of which a signal proportional to the measured pressure appears at the output of the measuring circuit.

At the places where the thin part of the membranes passes to the thick part, there are rounding radii that form a smooth extremum of bending stresses on the surface of the dielectric substrate in the zones of the strain gauge, which increases the overload capacity of the pressure measuring device, increases its operational reliability, long-term stability and performance.

Thus, as can be seen from the description of the device and its operating principle, a new technical solution is obtained, which ensures high sensitivity of the output signal, high measurement accuracy (0.05-0.1%), high linearity (0.1-0.25 %), low temperature coefficient of change of the initial signal when the temperature changes, high overload capacity, long-term stability of measurements, reliability in a wide temperature range (from minus 50 to plus 120 ° С and more), compactness and simplicity of design (for example, the outer diameter of membrane 1 for a nominal pressure of 400 kPa is 16 mm). A device for measuring pressure, made according to the description, it is advisable to use for the upper limits of pressure measurements in the range of 50-400 kPa in small-sized devices for pressure, vacuum, pressure difference, flow rate, level.

Compared with the prototype, the claimed utility model has a sensitivity of 1.5-2 times higher with similar overall dimensions, diameters and thicknesses of the membrane.

Claims (6)

1. A device for measuring pressure, containing a membrane having an outer thick ring, a thin part and a rigid center, and at least two strain gages placed on a dielectric substrate rigidly fixed to the upper surface of the measuring membrane, near the transition regions of the thin part to thick, different the fact that the dielectric substrate has an elongated rectangular shape with an aspect ratio of at least 3: 1, covering a smaller part of the surface area of the measuring membrane, and on the surface of the dielectric In the regions of transition of the thin part of the membrane to the thick part, both near the outer ring and near the rigid center, four strain-sensing resistors are placed that have the same orientation along the long side of the membrane or perpendicular to it. 2. The device according to claim 1, characterized in that on the dielectric substrate is additionally insensitive to deformation and temperature-sensitive resistor made of heteroepitaxial silicon or other material. 3. The device according to any one of claims 1 and 2, characterized in that the lower side of the receiving membrane can be rigidly connected to the housing of various shapes. 4. The device according to claim 1 or 3, characterized in that the adapter ring can be rigidly fixed to the outer thick ring of the measuring membrane. 5. The device according to claim 4, characterized in that the collector of dielectric material with metal contacts can be rigidly fixed to the adapter ring. 6. The device according to claim 5, characterized in that the cap of dielectric material can be rigidly fixed to the collector.