SU1334050A1 - Pressure of substances in pipeline - Google Patents

Description

one

The invention relates to a measurement technique and can be used to measure the pressure of substances in a pipeline.

A known capacitive pressure transducer of substances consisting of a pressure sensing membrane, a movable electrode of a capacitive transducer integral with the screen, and a fixed electrode forming an electrical capacitance with the membrane. A change in the pressure of a substance on a membrane leads to its movement and, consequently, to a change in the capacitance between the stationary electrode and the membrane, according to which the pressure of the substance is judged.

The disadvantage of this transducer is its low accuracy due to the influence of temperature and the action of corrosive environments surrounding the transducer, which during long-term operation cause corrosion of the electrode surface, change the distance between the fixed electrode and the membrane and cause a transducer capacitance deviation, which leads to conversion error.

The closest to the proposed technical essence and the achieved result is a device for measuring the pressure of substances in the pipeline, containing working and compensating electrical transducers of the deformation of the pipe, performed in the form of strain gauges, glued respectively around the circumference and forming the pipeline and connected in a bridge circuit.

This device has a small time stability of parameters, as well as a large error at high temperatures.

The purpose of the invention is to increase the accuracy of the pressure measurement.

The goal is achieved by the fact that the working transducer is made in the form of a capacitor formed by ring-shaped pipes covering the gap and axially spaced by two working electrodes and a common screen in the form of a hollow cylinder, the working electrodes are located on insulators inside this screen, and The compensation converter is made in the form of a second capacitor formed by one of the indicated working electrodes.

ten

34050. 2

opposite a neg-o on insulators inside a common screen, a compensation ring-shaped electrode, a common screen and an additional screen coaxial with a gap located between the compensation electrode and the pipeline.

The drawing is a device, general view,

The device contains a screen 1, high-grade 1 and 2 low-potential 3 electrodes, which form a working capacitor with a tube 4 in cross section, an insulator 5, a high-potential electrode 6 of a compensation capacitor with an additional screen 7. Measuring and compensating capacitors are included in the adjacent ple - 2Q Chi Transformer Bridge.

The Converter operates as follows.

A change in the pressure of a substance in a pipeline leads to a change in the external radius of the pipeline, which leads to a change in the capacitance of the working capacitor, which is fixed by the measuring circuit.

If a dielectric film is placed on the surface of the pipe, the capacitance C is

f

 / 2K. ё, H El 35

X (1-1p2) +.

...,

(one)

g

0

five

,, IP2

0

if the dielectric film is placed on a potential electrode, then

 1 + 2 1f9)

 where is the film thickness;

E is the dielectric constant of the film;

initial capacity of the cross capacitor;

H is the distance between potential or screen electrodes of a cross capacitor;

L is the average harmonic length of the capacitor.

During corrosion, dielectric films arise on the surfaces of screen and potential transducer electrodes, which in the first case cause a decrease in capacitance, and

in the second - an increase. The total change in the capacitance of the converter has a fourth order of smallness.

2b

((-)) which can be neglected, H

Since the initial capacitance C ,, of the converter is proportional to the dielectric potential B of the environment and the length of the electrodes L, to eliminate errors associated with the change of these factors, a compensation capacitor with potential electrodes 3, 6 and screens 1 and 7 is introduced. and compensating converters to the adjacent shoulders of a transformer bridge, the change in dielectric constant and ambient temperature does not affect the accuracy of the change with equal length L of both condensates. ditch

Editor M. Tsitkina

Compiled by A. Sokolovsky

Tehred M. Khodanich Proofreader A.Obruchar

Order 3957/41 Circulation 776 Subscription

VNIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Production and printing company, Uzhgorod, Projecto st., 4

To eliminate the error of the converter associated with the temperature change of the substance in the pipeline, the pipe, screen and electrodes of the device should be made of the same material,

In order to reduce the errors associated with the physicomechanical properties of the pipe, the calibration of the converter should be performed assembled.

The technical and economic efficiency of the image lies in the fact that the device makes it possible to increase the accuracy of pressure conversion by reducing the effect of corrosion during long-term operation, as well as by eliminating the effect of temperature and the dielectric constant of the environment.

Claims (1)

A DEVICE FOR MEASURING PRESSURE OF SUBSTANCES IN A PIPELINE, containing a working and compensating electric strain transducer, distinguishing with the fact that, in order to improve accuracy, the working transducer is made in the form of a capacitor formed by an annular, spanning pipeline with a gap and spaced apart axial direction by two working electrodes rf a common screen in the form of a hollow cylinder, and the working electrodes are located on the insulators inside this screen, and the compensation converter ying in "a second capacitor formed by one of said working electrodes mounted opposite to it on the screen within a common isolators annular compensation electrode common screen and additional screen coaxially disposed with a gap between the electrode and the compensating duct. 1334050 A1 1334050 2