RU1781574C - Pressure difference pickup - Google Patents

Abstract

Usage: in instrumentation and can be used to measure the differential pressure or flow rate of liquid and gas SUMMARY OF THE INVENTION: a rigid partition is placed in the sensor housing, on both sides of which membranes are made of elastic material. Under the action of the differential pressure, the console is made in a rigid partition deviates, and on the displacement transducer into an electric signal located in the groove of the rigid partition at the free end of the console, a mismatch signal appears, the value which is a measure of pressure. The transducer of movement into an electrical signal is made in the form of an eddy current sensor. 3 ill.

Description

The invention relates to instrumentation and can be used in the development of highly sensitive pressure difference converters, liquid and gas flow meters, and the like. appliances.

When diagnosing modern gas turbine engines (GTE), it is required to measure very small pressure drops of 10-5C 0 Pa in the frequency range 0-1000 Hz under conditions of high static pressure of 10 MPa or more.

Known pressure differential transducers containing receiving membranes and strain-gauge lever-membrane type. The pressure difference causes deflection of the membranes, which deforms the sensitive elements of the genomemodule by means of a lever. An electrical signal from the strain gauge module is applied to an electronic normalization amplifier.

Despite the fact that the known strain gauges are accurate and meet the requirements, they have the following disadvantages: zero offset of the output signal, and sometimes a change in characteristic over time; the effect of temperature on the readings of the converter, although it contains elements for temperature compensation,

In addition, they have large dimensions and weight, low reliability and high cost. The supply of strain gauges by the domestic industry is limited due to a shortage of semiconductor strain gauges,

The closest in technical essence and the achieved result is a parametric-type pressure difference sensor containing a housing with two inlet fittings, between which a transducer for displacement into an electrical signal and a rigid bulkhead is installed, on which both membranes are placed on both sides, and also a signal processing circuit.

The sensor is a capacitive type converter, on the rigid partition of which a central electrode is formed, and the membranes function as movable electrodes. Thanks to the rigid core connecting the centers with the membrane to their profiling, high metrological characteristics were achieved by converting the bodies.

However, the disadvantages of the sensor include a narrow range of operating pressures, the upper limit of which is not more than 0.15 MPa. Expanding the operating range of the sensor requires an increase in the thickness of the membranes, which is associated with the loss of its sensitivity. In addition, the known sensor has additional errors due to non-linearity (0.3%). hysteresis (0.5%) and

temperature (0.05%%

° C

An object of the invention is to increase the sensitivity of the sensor to high static pressure drops.

The goal is achieved in that in the pressure difference sensor containing the displacement transducer into an electric signal, a rigid partition and membranes, the displacement transducer is made in the form of an eddy current sensor, and a U-shaped through groove is made in the rigid partition to form a cantilever, while the eddy current sensor placed in the groove of the rigid partition in the area of the free end of the console, and the membranes are made of elastic material and are located on the surfaces of the rigid partition made of metal, and the length I onsoli selected from ratios

ugg

I

mk

where E is the modulus of elasticity of the material of the rigid partition;

b is the width of the console;

h is the thickness of the console;

mk is the mass of the console;

Tg is the pressure differential time.

In the known sensor, in contrast to the prototype, an elastic cantilever and a groove are formed in the rigid partition in which the current transducer is installed. This allowed on the one hand to increase the sensitivity of the converter by using the cantilever effect, and on the other hand, to expand its operating range due to the high mechanical strength of the sensor

- The totality of the signs given the totality is not found in the scientific, technical and patent literature. Individual features of the invention are known in other populations, where they are

various properties.

Known console with linear displacement of the free end, which is loaded with concentrated force F. In the proposed device, the console is made in one piece with a rigid partition and load. evenly distributed over its area by pressure. Since the cantilever deflection is proportional to the force F - PS, where P is the measured pressure, S is the area

console, the sensitivity of the converter can be significantly increased by using the area S of the console. The deviation of the free part of the cantilever is measured using an eddy current transducer. This solution made the eddy current transducer flat and installed at the end of the console in the groove of the rigid partition. In the present device, in addition to the well-known properties inherent in the considered features, there is a combination of such conditions that lead to the appearance of new features in these features.

So, a system consisting of a console and an eddy-current displacement transducer, unlike the prototype, is free from disadvantages such as hysteresis, nonlinearity, and temperature. The console has displacement from fractions of a micron to one millimeter and is made of high-quality temperature-resistant materials. Moving the end of the console measured by eddy current transducer having an operating range exceeding the range of movement of the console

In the inventive transducer, pressure sensing membranes are made of an elastic material. The main

the purpose of the membranes is to isolate the receiving chambers from each other. Since a pressure difference of the same order is measured, the requirements for the mechanical strength of the membranes are insignificant. They perceive

it’s only a pressure drop, and the opposing force, unlike the known devices, is created by the console itself. To exclude the possibility of membranes moving away from the console when measuring pressures below

the atmospheric cavity between them may be vacuumed

Compared to metal membranes, the receiving surface of which is limited by the nonlinearity of the transducer, the working surface of the console can be chosen large enough. It can be shown that the deviation D (5 of the end of the console under the action of the measured differential pressure A P is:

Lv

Et3

(1)

Where

- console length

t is the thickness of the console;

E is the modulus of elasticity of the material of the console.

As can be seen from the expression (1), the movement of the free end of the console depends on the length of the console to the fourth degree. Varying the length of the cantilever within small limits, it is possible to widely control the movement of its free end and obtain a correspondingly high resolution of the transducer. Having a set of identical plates with consoles of different lengths made in them, you can easily assemble the transducers for any pressure

It should be noted that the choice of console length is not unlimited. The maximum allowable cantilever length is limited by the differential pressure time. When designing the converter, it is necessary to choose the length of the console, starting from the expression.

s

0.3

E bh3rЈ

GG1k

where E is the modulus of elasticity of the material of the rigid partition;

b, h - width and thickness of the console;

mk is the mass of the console;

mp differential pressure time.

In FIG. 1 shows a rigid partition with a console, a displacement transducer and a normalizing amplifier; in FIG. 2 is a transverse section of the sensor, side view; in FIG. 3 is a waveform illustrating the operation of the converter.

The differential pressure sensor contains a rigid partition 1. in which the console is cut out by an electroerosive or laser method 2. The gap between the console and the partition is not more than 400 microns. A groove 3 is made in the partition, in which a vortex transducer 4 is installed. The gap between the ends of the displacement transducer and the console is 400 microns. The sensor output is connected to the filtration unit 5 and a normalizing amplifier 6. Elastic membranes 7 and 8 are applied on the surface of the partition from two sides. of thin rubber Partition 1, the transducer L displacement and

membranes 7.8 are installed between two pressure receiving chambers 9 and 10. The receiving chambers are provided with protrusions 11 and 12 to limit the travel of the console. The sensor assembly is secured with screws passing through

through holes 13 and 14.

The sensor operates as follows. If the pressures PI and P2 are equal, the console is in the neutral position and the signal output from the normalizing amplifier

equal to zero. At a pressure differential, when, the cantilever deviates from the equilibrium position in proportion to the measured pressure P. The cantilever deviation is measured using eddy current

a transducer, the signal from which, after filtering, enters the input of the normalizing amplifier 6. Due to the constructive isolation of the ends of the cantilever and the eddy current transducer, the sensor is insensitive to temperature changes. The effect of aftereffect and hysteresis in it is minimized due to the implementation of a partition made of a 70NHBMYu precision alloy, in which the physicomechanical properties are stable up to a temperature of 500 ° C. The resolution of the sensor is 10 Pa (see Fig. 3).

The use of the proposed technical solution in the national economy of the country will improve the accuracy and reliability of diagnostic tools for gas turbine engines, power plants, gas and oil pipelines, etc. equipment.

Claims (1)

The claims A pressure difference sensor comprising a housing with two supply fittings, between which a displacement transducer into an electrical signal and a rigid partition are installed, on which both membranes are placed on both sides, characterized in that, in order to increase the sensitivity, the displacement to electric signal transducer is made therein in the form of an eddy current sensor, and in the rigid partition a U-shaped through groove is made with the formation of the console, while the eddy current sensor is placed in the groove of the rigid partition and in the the rim end of the console, and the membrane where E is the elastic modulus of the rigid material Crayons are made of elastic material and partitions: located on the surfaces of a rigid partition made of metal, and the length I of the console is selected from a ratio of 5 b cantilever width, h - cantilever thickness: mk cantilever mass: gp differential pressure time. , / I V E b h3 Ј GPC b cantilever width, h - cantilever thickness: mk cantilever mass: gp differential pressure time. ... 2Y Fig. 1 w yr t l “T t: i, , hG2 H-i- J {- -L , jR $ f,%} Ј    ; ; r &/; Ј.,. Lza x1 u.J Jfvjl S, TAG G L U v (  ViUj-w. P i l ". K w iJ "i t r with i j" r Ј v d i f-f v tvwt w: G1, ". v s “- h“ TI TA v.gp; i {I g S S h j J & cW h-hr - - GtTO W- f bWldL; 4 $ rCfcf i jJiW + W MS r / - .it. V   ,,. -. -,, t s-jj yes, r .JlL.i jk SES SKsJS g j