SU712703A1 - Pressure sensor - Google Patents

Description

The invention relates to the field of instrumentation, in particular to devices for measuring pressure.

Known pressure sensors containing a cantilever fixed rod of semiconductor material with p - "junctions as a sensitive element [1] · The disadvantage of these sensors is either a low operating frequency or low sensitivity. I

A known pressure sensor containing a strain transducer and a pressure concentrator in the form of two elements with different volumetric stiffness, rigidly fastened together by the ends. One 1 pair of ends is fastened through a strain gauge transducer, for example, in the form of a p - "transition [2].

When the pressure changes, the elements, due to the difference in volumetric rigidity, move 2 by a different amount, as a result of which the strain gauge transformer is deformed, its electrical resistance changes, and a signal appears on the output of the measuring circuit, 2 proportional to the value of the measured pressure.

The disadvantage of such a sensor is a decrease in the accuracy of pressure measurement under conditions of uncontrolled fluctuations with the ambient temperature due to the high sensitivity to temperature due to differences in the temperature coefficients of linear expansion of the concentrator elements.

The selection of a pair of elements with the same temperature coefficients of linear expansion and significantly different volumetric stiffness is difficult in accordance with the general physical laws?. !!! that relate the pressure and temperature compressibility of solids (for example, through the Grüneisen relation).

The purpose of the invention is to improve the accuracy of pressure measurements.

This goal is achieved by the fact that in a pressure sensor containing a strain gauge transducer and a pressure concentrator of two elements with different volumetric stiffness, rigidly fastened to each other by ends, one of the elements of the pressure concentrator is made of two parts, temperature 5 is the coefficient of linear expansion coefficient ccj of the first of is greater than, and the second ₂ and - lower temperature coefficient of linear expansion al another element interconnected through tenzoelek0 trncheskpy transducer, The longer the

Z] and Ζ ₂ parts satisfy the relation

Z,, Ζ ₂

--H tp-h + ι> L + A

3 '(1)

This embodiment of the pressure sensor 5 avoids the appearance of a mechanical force acting on the tensoelectric transducer from the pressure concentrator when the ambient temperature changes. As a result, the accuracy of pressure measurements is substantially increased.

The drawing schematically shows the proposed sensor.

The sensor contains a strain gauge 15 transducer 1, a pressure concentrator in the form of two elements 2 and 3 with different volumetric stiffness, rigidly fastened together by the ends. One of the elements 2 is made of two parts 4 and 20 5, interconnected via a strain gauge transducer 1. To connect the strain gauge transformer 1 to the measuring circuit, electrical outputs 6 are used. 25

The volumetric stiffness of the element 3 is determined by its linear dimensions and volumetric stiffness modulus a _{3 of the} material from which it is made.

The volumetric stiffness of element 2 is determined by the linear dimensions of parts 4 and 5 and the volumetric stiffness modules of the materials from which they are made. The linear dimensions of the strain gauge, as a rule, are much smaller than the sizes of 35 parts 4 and 5. Therefore, the absolute deformation of element 2 in the direction of the compression axis of the strain gauge per unit pressure is

1 ⁴ θ ./ q__L. 1

Зх, ^{1 Н} Зх, ² 'where and are the bulk moduli of the materials from which the parts of the composite element are made. 45

In order for the concentrator to efficiently convert pressure to strain of the strain gauge transducer, the condition

C ₊ 1 Z ₂ I ⁵⁰

Xi l \ -P 1% Xg Z, 4- Z ₂ x ₃

i.e., different volumetric stiffness of the elements.

To exclude the influence of temperature changes on the strain of the strain gauge transducer, the lengths of the parts of the composite element are selected from condition (1).

In the event of a change in pressure, the concentrator elements 60 due to differences in volume

Order 2782/2 Ed. Number 117 Draw 1033

Printing house, 2 Sapunova ave.

The NPO “Search” stiffness changes its linear dimensions by a different value, as a result of which the strain transducer is deformed. In this case, its electrical characteristic changes and a signal proportional to the value of the measured pressure appears at the output of the measuring circuit. Due to the equality of the temperature coefficients of the linear expansion of the concentrator elements, the tensoelectric transducer does not deform when the temperature changes and a signal proportional to the temperature change does not appear at the output of the measuring circuit.

Claims (1)

Claim A pressure sensor comprising a strain gauge transducer and a pressure concentrator of two elements with different volumetric stiffness, rigidly fastened to each other by ends, characterized in that, in order to increase the accuracy of measurements, one of the elements is made of two parts, the temperature coefficient is "1 linear expansion the first of which is larger, and the second a ₂ is less than the temperature coefficient a _{3 of the} linear expansion of another element, interconnected via a strain gauge transducer, and the length n / ₂ parts satisfy the relation