SU759941A1 - Capacitive once-through sensor - Google Patents

Description

The invention relates to a measuring technique and can be used to study various liquid and gaseous media, as well as to control their quality 5 directly in the main pipelines of industrial installations and devices in chemical, petrochemical, oil refining and other industries. YU

Known capacitive flow sensor designed to measure the dielectric constant or electrical conductivity of liquids, containing two coaxial electrodes, internal and external, centering insulating rings, channels for input and output of the source of liquid, in this sensor are applied metal-ceramic washers installed in the end parts of the inner electrode [1].

Disadvantages! Such a sensor are low sensitivity and 25 large hydraulic resistance to flow through the sensor. Attempts to increase sensitivity by increasing the size of the electrodes and reducing 30

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the distances between them lead to a decrease in measurement accuracy due to the deterioration of the dynamic properties of the sensor.

Also known is a flow-through sensor of fluid density of a capacitive type, comprising a housing and a flat multiplattine capacitor made in the form of two insulated packages of flat plates of different polarity fixed in the slots of the housing [2].

The disadvantages of this design is the lack of rigidity of the electrodes, the unevenness of the electric field between the capacitor plates and a small specific capacitance.

The closest technical solution is a capacitive sensor consisting of a housing with a lid, fittings for entering and exiting the product under study, coaxial electrodes and means for fastening them, with aluminum contributions being used to center the electrodes [3].

Grounded pins and metal liners significantly violate the uniformity of the electric field between the electrodes of the capacitor and

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reduce their useful area, which reduces the accuracy of measurements, and with it the sensitivity. In addition, the increase in the number of coaxial electrodes in this design is associated with an increase in the number of conclusions, which in turn leads to an increase in the parasitic capacitance of the sensor. .

The disadvantages of the known design can be attributed to the complexity of maintenance during maintenance work.

The aim of the invention is to improve the sensitivity and accuracy’'measurement of the electrophysical parameters of various liquid and gaseous media in the stream. '.

The goal is achieved by the means for fixing coaxial electrodes in the proposed coaxial capacitive flow-through sensor made in the form of two cross-shaped bases interconnected by an insulating rod, on which two packs of coaxial electrodes of different polarities are fixed on the center of the sensor cover, provided with a direction; grid and a collector, with ¹ distribution grid installed at the sensor input.

The proposed means for attaching the coaxial electrodes maximizes the utility area of the electrodes, 'without violating the uniformity of the field' in me'Zhelektrodnom space, greatly reduce the parasitic capacitance "7 ^ e $ 's ~ vEY1Shv" de ^l * ^ u p' Tai “kyuyu''k- the number of electrodes almost does not render! influence on the magnitude of the parasitic capacitance conclusions. The use of a grating jointly in the sensor of distribution guides together with a collector allows to evenly distribute the flow in the interelectrode spaces of the multi-plate capacitor and eliminates the possibility of the formation of stagnant zones. Since any capacitive 'sensor gives an integral assessment of the electrophysiivcbqgd'd ......

parameter, the irregularity of the flow d "interelectrode spaces and the presence of stagnant zones can introduce significant errors in the measurement result, and the magnitude of this error will depend on the rate of change of the environment parameters. Thus, the proposed design of a multi-plate coaxial flow sensor allows to increase the sensitivity and accuracy of measurement electrophysical parameters of various liquid and gaseous media.

In order to create comfort when carrying out maintenance work

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....... The hooplate coaxial capacitive flow-through sensor is made collapsible.

FIG. 1 shows a multi-plate coaxial capacitive flow sensor in section; in fig. 2 5 section aa in fig. one.

The sensor has a housing 1 with a lid 2 screwed onto it. In the center of it a top base 3 is fixed on the thread with a set of coaxial electrodes 4 forming a package of one polarity with soldering or welding power.

Another packet is inserted into the annular gaps between the electrodes of this package.

15 coaxial electrodes 5 of reverse polarity, mounted in the same way as the first one on the lower base 6, which is connected to the upper base on an insulating thread.

20 rod 7, located in the center of the grounds. The coaxiality of the coaxial electrodes during installation is provided by concentric grooves 8, made in the bases. The sensor is sealed by two shims 9,10. To create uniform flow in the interelectrode; ·· spaces in the lower part of the corpus installed distribution grid 11, reinforced with a ring 12, and at the output of the sensor has a guide grille 13, made in the lid, and the collector 14, The sensor is equipped with fittings inlet 15 and output 16 of the product. Electrical output For one package of electrodes, the case itself serves, and output 17 from another package of electrodes passes through the center of the sensor and is isolated from the first output ’by insulator 18.

40 ‘In FIG. 2 shows the section of the sensor AA-A, on which the construction of the upper cruciform base 3 is clearly visible. Structurally, the lower base is made similar to 45 but the upper one.

The device works as follows. in a way. The output of the 17th case 1 is connected to a dielectric meter with the help of a coaxial cable.

50 permeability or conductivity. In the general case, the sensor can be connected to an AC bridge with a §-meter or 2-meter. Investigated flow of liquid or gas from the main pipelines through the nozzle. 15 enters the body 1 of the sensor, and

then through the distribution grid 11 passes into the interelectrode spaces formed by packages of coaxial electrodes 4.5.

60 Next, the flow passes through the guide grate 13, is collected in the collector 14 and is returned back to the main line through the outlet fitting 16 ′. Changes in the electrophysical parameters of the meters studied or controlled ν 4

759941

the substance passing through the sensor, such as dielectric constant, conductivity, dielectric loss tangent, etc. cause a change in the electrical parameters of the capacitive sensor, which are fixed by the measuring device.

The use of this sensor will increase the sensitivity of measurements due to the most complete use of useful electrode area, as well as increase the accuracy of electrophysical measurements by eliminating the non-uniformity of the electric field between the coaxial electrodes, reducing the parasitic capacitance of the sensor terminals and leveling the flow of material that runs through the sensor. y-

Claims (1)

Claim Capacitive flow sensor consisting of a housing with a lid, fittings for inlet and outlet of the product under investigation, coaxial electrodes and means for their attachment, distinguished by the fact that, in order to increase the sensitivity and accuracy of measurement; . The means for fixing coaxial electrodes is made in the form of two cross-shaped interconnected by an insulating rod. bases on which two coaxial packages are rigidly fixed There are 10 electrodes of different polarity, and the capacitor thus formed is fixed in the center of the sensor cover, fitted with a guide grid and a collector, with a distributor installed at the entrance to the sensor? telny lattice. "