RU2330251C1 - Density pickup - Google Patents

Abstract

FIELD: microelectronic instrument making.

SUBSTANCE: density pickup has a casing accommodating a measuring vertically arranged membrane forming a tight chamber inside the casing and a strain converter, the said chamber being filled with a liquid. The said strain converter interacts with the membrane to record the angle (force) of the membrane central part about horizontal axis by means of a rod connected to the membrane central part and arranged perpendicular to its plane. Here note that rod end can be coupled with the strain converter or the casing by a flexible linkage oriented perpendicular to the rod axis along the top-bottom direction. The membrane edges are, preferably, made corrugated and elongated in the vertical shape direction with the relation between the longer and shorter sides equal to 1.5-3. The tight chamber is filled with vacuum-treated silicon-organic liquid.

EFFECT: simpler design and higher accuracy.

7 cl, 4 dwg

Description

The invention relates to microelectronic instrumentation and can be used in the construction of a wide class of microelectronic devices equipped with a sensitive element of the membrane type, in particular density sensors.

Known membrane densitometer, which is an elastic rubber caps, tightly worn on metal boxes, the cavities of which are connected by impulse tubes with a mercury differential pressure meter (IP Glybin. Automatic densitometers. Technique, Kiev, 1965, p. 93-94).

A disadvantage of the known densitometer with air filling of the system is that these devices are reliable in operation only with a special method of filling the system with air, certain conditions for the deformation of the membrane caps and a rational form.

A known membrane-type sensitive element containing a single-crystal silicon substrate with a basic orientation, a membrane comprising a layer of silicon nitride and silicon carbide located above the hole made in the substrate for forming the membrane chamber, and an informative signal pickup unit based on the end fiber optic Fabry-Perot interferometer, which is installed with the possibility of recording the deflection of the membrane (RF Patent No. 2247443, IPC H01L 29/84, 2003).

A disadvantage of the known device is the design complexity.

A known density sensor membrane assembly comprising a housing, an elastic flat or corrugated membrane fixedly mounted inside the housing, and an adjustment device, characterized in that the adjustment device consists of a membrane tension corrugation, an elastic spacer ring, a conical cracker, a micrometer screw and a reading device ( RF patent No. 2280242, IPC H01L 7/08, 2006).

A disadvantage of the known device is the inability to measure the density of the material, which narrows the scope of its application.

The prototype of this invention is a pressure difference sensor containing a housing attached to it with the formation of two sealed and two open chambers filled with evacuated organosilicon liquid, one measuring and two separation membranes (Pressure difference sensors Metran-44-DD. Nomenclature catalog. Issue 2.01. Group Metran enterprises. Pages 43, 46).

The disadvantage of the prototype is that interference from excessive pressure, forces from thermal expansion and the measured force, i.e. weight of liquid column, act in one direction. Therefore, in order to distinguish a relatively weak signal about the density, it is necessary to select the membranes very precisely according to their rigidity, and to control the volumes. The amount of fluid in the cavity plays a very important role, since its compressibility affects the readings of the sensors. The prototype design is rather cumbersome, since it contains at least three membranes, a lot of metal-to-metal seals (rubber seals are not allowed, since they are compressed at high pressures and change the volume of the cavities). In addition, leaks are possible through the rubber, which distorts the readings (zero floats).

The objective of the invention is to simplify the design and improve the accuracy of measuring the density of the material.

This technical result is achieved due to the fact that in the density sensor comprising a housing mounted therein with the formation of a sealed chamber, a measuring membrane oriented vertically and a strain gauge, the chamber being filled with liquid, additionally the strain gauge interacts with the membrane with the possibility of detecting rotation angle (force) its central part around a horizontal axis. Alternatively, a rod located perpendicular to the plane of the membrane is attached to the membrane in its central part, through which the strain gauge interacts with the membrane. The end of the rod can be connected to the strain gauge by a flexible connection, oriented perpendicular to the axis of the rod in the direction of the top-bottom. The end of the rod can also be connected to the housing by a flexible connection, oriented perpendicular to the axis of the rod in the top-bottom direction. Preferably, the membrane at the edges is corrugated and is made elongated in the vertical direction of the form with a ratio of the lengths of the larger and smaller sides of 1.5-3. The sealed chamber is preferably filled with evacuated organosilicon liquid, for example PMS-300.

The invention is illustrated by drawings, where

figure 1 shows a density sensor with a round membrane and with a rod connected to a strain gauge, a longitudinal section;

figure 2 is the same front view;

figure 3 - density sensor with an elongated membrane and with a rod connected to the housing, a longitudinal section;

figure 4 is the same front view.

The positions in the drawings indicate: 1 - housing, 2 - sealed chamber, 3 - membrane, 4 - strain transducer, 5 - rod, 6 - flexible connection.

The density sensor comprises a housing 1, in which a vertically oriented measuring membrane 3 is mounted with the formation of a sealed chamber 2. A strain gauge 4. mounted in the housing 1 interacts with the membrane 3 to register the angle (force) of rotation of its central part around the horizontal axis 4. For this, in the central part of the membrane 3, a rod 5 interacting with the strain gauge 4 located perpendicular to the plane of the membrane 3 is attached to it. The end of the rod 5 can be connected to the strain gauge 4 with a flexible connection 6, oriented perpendicular to the axis of the rod 5 in the direction of the top-bottom. The end of the rod 5 can also be connected by a flexible connection 6, oriented perpendicular to the axis of the rod 5 in the direction of the top-bottom with the housing 1. Preferably, the membrane 3 at the edges is made corrugated and elongated in the vertical direction with a ratio of lengths greater than “a” and smaller “b” sides 1,5-3. The sealed chamber 2 is filled with a high compression ratio liquid, preferably an evacuated organosilicon liquid, for example PMS-300. In a preferred embodiment, its amount is minimal, which is determined from structural considerations by minimizing the volume of the sealed chamber 2. Outside of the membrane 3, a rubber membrane (not shown) can be fixed.

The density sensor operates as follows. The membrane 3 perceives the external pressure of the medium acting on it. Since at this pressure there is a component of the weight of the column of the environment caused by its density, its value varies in height: it is larger in the lower part of the membrane and less in the upper. The total pressure of the column of the external environment and other external sources, including from the thermal expansion of the liquid, is symmetric about the axis of the membrane and is balanced by the back pressure of the incompressible evacuated organosilicon liquid, the amount of which is also minimal. Under the influence of pressure varying in height, the membrane 3 takes a curved shape: concave in its lower part and convex in the upper. As the measured factor, the angle of rotation of the central part of the membrane 3 relative to the horizontal axis of symmetry when bending is used, as measured by the strain gauge 4.

To obtain information about the density of the environment by the angle of rotation of the central part of the membrane 3 relative to the horizontal axis of symmetry, when it is bent, the density sensor is checked against calibration liquids separately from the measurements.

By calculating the integral values of the pressure of the liquid column on the vertically arranged membrane 3, it can be determined that the magnitude of the moment relative to the horizontal axis of symmetry for the round membrane 3 (Fig.1, 2)

,

,

where ρ is the density of the medium, R is the radius of the membrane 3, i.e. increases sharply with increasing membrane size 3.

Also the magnitude of the moment relative to the horizontal axis of symmetry for elongated in the vertical direction of the membrane 3 (Fig.3, 4)

,

,

where l is half the distance of the centers posting (figure 3).

From these dependencies it follows: the implementation of the membrane 3 elongated in the vertical direction of the form allows you to take in more torque due to the pressure of the liquid due to the increase in elevation and, accordingly, caused by this pressure drop. At l = R, it is 4.03 times the moment on the round membrane 3. At values less than 1.5, the effect of elongation of the membrane shape is insignificant, at large 3, the deformation of the corrugations increases significantly. The connection of the rod 5 with the strain gauge 4 by means of a flexible connection 6 allows you to unload the system from external pressure. At the same time, the rod 5 serves as a support to which the torque transmitted by the membrane 3 and, accordingly, the voltage to the strain gauge are transmitted. The transverse force is transmitted to seal the membrane 3 near its middle part, since this is the minimum and most rigid (along the corrugations) transmission of force, without significantly affecting the freedom of rotation of the membrane 3. The number of seals in the proposed device is minimal. In the case of welding, there are only two of them - a pressure seal and a screw. In an embodiment of the device without welding, a back cover seal is added to these two.

The parameters are substantiated and detailed documentation for the manufacture of a prototype is developed.

Thus, the application of the invention allows to simplify the design and improve the accuracy of measuring the density of the material.

Claims (7)

1. Density sensor, comprising a housing mounted in it with the formation of a sealed chamber, a measuring membrane oriented vertically, and a strain gauge, and the chamber is filled with liquid, characterized in that the strain gauge interacts with the membrane with the possibility of recording the angle (force) of rotation of its Central part around the horizontal axis. 2. The density sensor according to claim 1, characterized in that a rod located perpendicular to the plane of the membrane is attached to the membrane in its central part, through which the strain gauge interacts with the membrane. 3. The density sensor according to claim 2, characterized in that the end of the rod is connected to the strain gauge by a flexible connection, oriented perpendicular to the axis of the rod in the up-down direction. 4. The density sensor according to claim 2, characterized in that the end of the rod is connected to the housing by a flexible connection, oriented perpendicular to the axis of the rod in the up-down direction. 5. The density sensor according to claim 1, characterized in that the membrane is corrugated at the edges. 6. The density sensor according to claim 1, characterized in that the membrane is made elongated in the vertical direction of the form with a ratio of the lengths of the larger and smaller sides of 1.5-3. 7. The density sensor according to claim 1, characterized in that the sealed chamber is filled with evacuated organosilicon liquid.

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