SU1631326A1 - Pressure measuring device - Google Patents

Abstract

The invention relates to a measurement technique, in particular to pressure sensors. The aim of the invention is to reduce the nonlinearity of the output characteristic due to the reduction of errors caused by the non-linear dependence of the measurement result on the size of the gap between the electrodes, and the elimination of errors caused by the non-planarity of the surfaces of the electrodes. The goal is achieved by additionally introducing into the device an auto-generator 7, a voltage amplitude meter 3 and a fixed electrode 6 forming a flat capacitor with the moving electrode 3, one edge of the moving electrode 3 fastened to the membrane 2 and the other moving freely around the fixed axis of rotation. The stationary electrode 6, having a uniform resistive resistance, is isolated from the housing 1, the conclusions of the autogenerator 7 are connected to opposite terminals of the resistive stationary electrode 6, and the voltage amplitude meter 3 is connected to the moving electrode 3 and the common output of the autogenerator 7. 3 Il. with SS C / 3

Description

The invention relates to a measurement technique and can be used to measure the pressure of liquid and gaseous media or small movements.

The purpose of the invention is to reduce the nonlinearity of the output characteristic.

Figure 1 is a diagram of the proposed pressure gauge; Fig. 2 is an electrical replacement circuit for a pressure sensor; in FIG. 3, the output characteristics DL / I0 f, (r) of the proposed device for different values of b.

The pressure gauge includes a sensor comprising a housing 1, on

which is rigidly fixed around the perimeter of the pressure-sensitive membrane 2, made in the form of an elastic plate, a movable electrode 3, electrically isolated from the membrane 2 and fastened to it with one edge at the central point of the membrane 2 using a pin 4, which is spring-loaded spring 5, and the other edge the moving electrode 3 moves freely around a fixed axis of rotation, a fixed electrode 6 having a uniform resistive resistance and forming a flat capacitor with a moving electrode, an autogenerator 7, the conclusions of which th connected with vyvotl

С & СО

with

05

The resistive layer of the fixed electrode 6 and the voltage amplitude meter 3 connected to the movable electrode 3 and the common output of the oscillator 7.

The electrical replacement circuit of the pressure sensor is shown in Fig. 2, where RO is the impedance of the resistive layer of the fixed electrode (between opposite terminals); C is the capacitance between the surfaces of the movable and stationary electrodes and reduced to the electrical center, whose position is determined by the equality of the distributed capacitances on both sides relative to this center; & R is the change in the resistance of the stationary electrode area determined by the distance between the electric center with parallel movable and stationary electrodes, and the electric center determined by the movement of the movable electrode under the action of the membrane.

The pressure gauge operates as follows.

When the power is turned on, the autogenerator 7 generates a alternating voltage with amplitude U0, which is applied to the terminals of the fixed electrode 6. As a result, the voltage amplitude meter 8, whose input resistance is much greater than the resistance introduced by the communication capacitance, will fix the voltage Ugc) y equal to

Rjj / 2jL4R RO

 t. about ± 21ЛК

 U0 7 P

willow io

2- Rc

where R p-1; p - running resistance; 1 is the distance between the electrical centers for parallel and skewed electrodes.

The change in resistance D R is proportional to the displacement of the electric center, which is dependent on the displacement g of the edge of the moving electrode 3 under the influence of pressure (Fig. 2a). For the analysis of the nonlinearity error, we divide the flat capacitor formed by the moving to the stationary electrodes along the length into infinitely small sections of length dj (

ten

15

(1C

Ј60ndx

b - xtgfll

where C is the relative dielectric constant of the medium; 50 absolute dielectric

vacuum permeability; n is the width of the resistive layer; b is the distance between the surface of the stationary electrode and the axis of rotation of the movable electrode; On - the angle between the movable and stationary electrodes; X - the current coordinate of the area under consideration. At small angles оЈ tg About «0 Regarding the electric cent

See SSPrava, i.e.

  f ..

Jb - xrf. b

-bfZ

Integrating, we get

ln (b - - In (b-xoi) b b + y

-e / 2

t

4zo - Y y

 L2-OL 12/4

(b-yoO

From here

35 bibLi ii M

Have

06

Let us express the displacement of the electric center y through the displacement of the edge of the mobile electrode g, since (to tg o

2nd - d for small g, then

45

- -2-1- a, -F

-g.

Since the fixed electrode 6 has a uniform resistance, the sensitivity of the proposed sensor is determined as follows.

i UebW

2r

Ur i

R; r (b - Jb2 - r2).

(2)

Increasing the linearity of the output characteristic is achieved by

The fact that the nonlinearity of the dependence of the resistance on the magnitude of the displacement of the membrane is less than the nonlinearity of the dependence of the capacitance on the analogous displacement of the membrane (in the known meter) is approximately an order of magnitude. sensor.

Claims (1)

Invention Formula A pressure gauge comprising a pressure sensor with a housing, a membrane mounted therein and connected to the center of the membrane and insulated from it by a movable electrode located on the side of the membrane opposite to the supply side of the measured medium, characterized in that, in order to reduce the nonlinearity of the output characteristic, he introduced an oscillator and a voltage amplitude meter, and a fixed electrode, having a uniform resistive resistance, was additionally inserted into the pressure sensor; A flat capacitor that connects with a movable electrode and a rotating axis of the movable electrode are installed in the center of the membrane, with one end of the movable electrode mounted on the axis of rotation, and the other free is connected to a voltage amplitude meter connected to one of the outputs of the autogenerator, and the fixed electrode is insulated from the case and with their ends connected to the terminals of the oscillator. 1J- + & R $ g- ± hR T 0 FIG. 2 nonlinearity OM 1020JO Fig.Z BO, MKN